WEBVTT 1 00:00:00.440 --> 00:00:03.240 Okay, So our next section we're going to talk about 2 00:00:03.720 --> 00:00:10.080 basics of digital modes, packet receiving, transmitting, digital mode, digital operation, 3 00:00:11.039 --> 00:00:13.759 digital modes. It's gonna be a lot of fun, all right. 4 00:00:14.759 --> 00:00:17.120 So some of the basics of a digital mode where 5 00:00:17.160 --> 00:00:22.079 to find digital activity. So communications are digital modes if 6 00:00:22.120 --> 00:00:26.760 the information is exchanged as individual characters encoded as digital 7 00:00:26.839 --> 00:00:32.079 bits such as Morse code, radio, teletype PSK, thirty one 8 00:00:32.200 --> 00:00:35.320 ft eight D star, DMR, slow scan TV, those are 9 00:00:35.320 --> 00:00:41.359 all forms of digital modes. Digital modes are restricted to 10 00:00:41.479 --> 00:00:46.640 CW SLASH data segments and the HF bands. They're found 11 00:00:46.719 --> 00:00:51.000 near the top of the CW segment on twenty meters. 12 00:00:51.000 --> 00:00:54.920 Most PSK stations are near fourteen seventy r TTY, other 13 00:00:55.039 --> 00:01:01.000 modes between seventy and fourteen. Table coming up to show 14 00:01:01.039 --> 00:01:04.319 some of that. CW isn't formally restricted anywhere in the bands. 15 00:01:04.319 --> 00:01:06.359 It's a digital mode, but you can use it anywhere. 16 00:01:06.799 --> 00:01:13.400 They has special privileges. Data rates and bandwidths are specified 17 00:01:13.439 --> 00:01:17.239 by the FCC rules. Digital codes not specified by the 18 00:01:17.280 --> 00:01:21.280 FCC must be public. You can have an experimental mode, 19 00:01:21.319 --> 00:01:23.120 but it's got to be published. People have to know 20 00:01:23.159 --> 00:01:27.840 what it is. Radio teletype originally used mechanical teleprinters, but 21 00:01:27.959 --> 00:01:31.480 migrated as computer sound cards. Most people use a computer 22 00:01:31.560 --> 00:01:33.879 sound card to generate their digital tones in these days. 23 00:01:34.719 --> 00:01:37.920 PSK thirty one Real, Real Popular, it's a good Week. 24 00:01:38.000 --> 00:01:43.840 Signal mode uses load transmit, packet teletype over radio win 25 00:01:43.959 --> 00:01:49.640 more is Windows based messaging over radio win war All 26 00:01:49.719 --> 00:01:53.799 those are popular types of HF digital modes. And there's 27 00:01:53.840 --> 00:01:57.359 packet radio common on VHF U HF twelve and nine 28 00:01:57.439 --> 00:02:02.560 six hundred bought on those bands. Okay, so here's the bands, 29 00:02:02.560 --> 00:02:05.280 here's the frequency range or where you will find some 30 00:02:05.319 --> 00:02:09.120 of the digital stuff hanging out. Most people here to 31 00:02:09.159 --> 00:02:13.000 that's pretty people follow it pretty well. So here's some 32 00:02:13.080 --> 00:02:16.759 definitions you might want to know for digital stuff. Airlink 33 00:02:16.879 --> 00:02:19.560 that's the part of the comp system that involves radio 34 00:02:19.599 --> 00:02:23.599 transmission and reception of signals. I don't think I've ever 35 00:02:23.680 --> 00:02:27.599 used that much, but air that's an airlink. Bit is 36 00:02:27.639 --> 00:02:30.280 the fundamental unit of data, as zero or a one, 37 00:02:31.159 --> 00:02:34.719 representing all the part of a binary number. There's the 38 00:02:34.759 --> 00:02:37.800 bit rate. That's the number of digital bits per second 39 00:02:38.199 --> 00:02:42.400 sent from one system to another. Bod is a number 40 00:02:42.439 --> 00:02:47.400 of symbols per second, and Symbols can be ten bit 41 00:02:47.520 --> 00:02:50.520 or eight bit based on the protocol you're using, but 42 00:02:50.599 --> 00:02:53.599 it's symbols per second sent from one station to another. 43 00:02:54.039 --> 00:02:55.960 The duty cycle is the ratio of the time that 44 00:02:56.000 --> 00:02:58.800 the transmitter is on to the total time plus the 45 00:02:58.879 --> 00:03:03.319 off time. Protocol are the rules that control the method 46 00:03:03.400 --> 00:03:07.280 used to exchange data between systems, and the mode is 47 00:03:07.280 --> 00:03:11.919 the combination of a protocol with the modulation method. Digital 48 00:03:11.960 --> 00:03:16.560 modes are regulated as voice emissions by the FCC. Digital 49 00:03:16.639 --> 00:03:21.599 Voice modes and those include d STAR System, fusion AR 50 00:03:21.879 --> 00:03:28.120 Digital Voice System d DMR. FSK individual bits of data 51 00:03:28.199 --> 00:03:32.919 encoded as tones. FSK uses tones as data are transmitted. 52 00:03:32.960 --> 00:03:35.759 Different tone frequencies are used to represent the one or 53 00:03:35.759 --> 00:03:39.080 the zero. The frequencies in a two tone FSK system 54 00:03:39.199 --> 00:03:43.319 called mark in space, space represents a zero and mark 55 00:03:43.400 --> 00:03:48.599 represents a one. In direct FSK, the frequency of the 56 00:03:48.599 --> 00:03:52.400 transmitter's BFO is controlled by a digital data signal from 57 00:03:52.400 --> 00:03:55.599 the computer, So either can send two tones through the 58 00:03:55.639 --> 00:04:00.120 audio passband or you can actually change the carrier frequency 59 00:04:00.960 --> 00:04:04.759 the same thing. It's a frequency shift. It's the same 60 00:04:04.759 --> 00:04:09.479 result audio frequency shift K, which is probably ninety eight 61 00:04:09.520 --> 00:04:11.439 percent of what we do in the hand radio is 62 00:04:11.560 --> 00:04:15.000 use audio tones modulated on single sideband or FTEM through 63 00:04:15.000 --> 00:04:21.240 the microphone input generated by a sound card. Typically, multiple 64 00:04:21.279 --> 00:04:23.519 FSK uses more than two tones and are used to 65 00:04:23.560 --> 00:04:31.439 create more codes. Most common type of the fs the 66 00:04:31.639 --> 00:04:35.639 PSK the face shift king. Most common type of face 67 00:04:35.680 --> 00:04:40.000 shift is to invert one of the tone waveforms by 68 00:04:40.000 --> 00:04:43.800 shifting at one hundred and eighty degrees. Rapid changers and 69 00:04:43.959 --> 00:04:47.199 face can be heard from from the human ear as 70 00:04:47.240 --> 00:04:50.639 a rasp, noise or buzz. The signature of a PSK 71 00:04:50.759 --> 00:04:54.079 sitting on the air received by by CW or CW 72 00:04:54.680 --> 00:04:58.240 single sideband receivers sort of sound like an old computer mode. 73 00:05:00.199 --> 00:05:02.399 Let's let's talk about some questions here in what segment 74 00:05:02.439 --> 00:05:05.399 of the twenty meter band are most digital modes operations 75 00:05:05.439 --> 00:05:12.800 commonly found. It's around between fourteen seventy and four D. 76 00:05:13.839 --> 00:05:20.680 What is a direct binary FSK modulated signal direct? Now 77 00:05:20.680 --> 00:05:23.120 we're doing direct, so you want to key the oscillator 78 00:05:23.160 --> 00:05:28.240 directly with their digital signal? Must be v okay. How 79 00:05:28.439 --> 00:05:32.040 are the two separate frequencies of a frequency shift key 80 00:05:32.199 --> 00:05:39.040 signal identified? Usually do marking space? Which of the following 81 00:05:39.079 --> 00:05:44.399 provided digit number of digital voice modes Okay, remember digital 82 00:05:44.439 --> 00:05:49.199 voice modes DMR D Star infusion. Those are digital voice modes. 83 00:05:49.240 --> 00:05:54.319 All these other ones have non voice modes. Okay, talk 84 00:05:54.360 --> 00:05:59.519 about some character based modes. Simplest use of digital communications 85 00:05:59.759 --> 00:06:03.199 as mode in which individual characters entered by an operator 86 00:06:03.279 --> 00:06:05.800 and transmitted to another station and they appear on another 87 00:06:06.240 --> 00:06:12.279 by another read by another operator, such as Morse code. Uh. 88 00:06:12.439 --> 00:06:15.199 Speeds are low but convenient to use and require a 89 00:06:15.199 --> 00:06:18.199 little additional equipment than a sound card or modem. So 90 00:06:18.279 --> 00:06:20.759 a lot of times it's a keyboard to keyboard. I 91 00:06:20.800 --> 00:06:24.079 typed the letter A, I transmitted it, and receive station 92 00:06:24.160 --> 00:06:26.279 gets it puts on his computer A. So we just 93 00:06:26.360 --> 00:06:30.720 did some character based transmission, sometimes referred to as keyboard 94 00:06:30.720 --> 00:06:34.560 to keyboard or chat. You transmit a stream of characters 95 00:06:34.600 --> 00:06:39.600 without additional data. That's referred to as unstructured. Oldest form 96 00:06:39.639 --> 00:06:44.439 of hand radio digital communication is r tt Yuh. This 97 00:06:44.759 --> 00:06:47.839 you sends the This is called BOTTO. It's a timing 98 00:06:47.839 --> 00:06:51.439 sequence for the bit pattern. Uh. Here we're trying to 99 00:06:51.480 --> 00:06:54.000 send the letter DS and dog. It starts a bit 100 00:06:54.120 --> 00:06:56.240 is set. You have some bits that tell it when 101 00:06:56.240 --> 00:06:59.120 it's starting. Then the data comes across and then you 102 00:06:59.160 --> 00:07:03.720 get a stop bit and you're done, and how fast 103 00:07:03.800 --> 00:07:09.480 it goes out is a bawd raad okay. R t 104 00:07:09.600 --> 00:07:12.560 t Y uses the BODO code, which is which represents 105 00:07:12.600 --> 00:07:15.720 each character has a five bit sequence. Five bit allows 106 00:07:15.759 --> 00:07:18.319 for thirty two different characters. That's not enough for their 107 00:07:18.399 --> 00:07:23.040 attire English language, you know, numerals and punctuation. There's two 108 00:07:23.079 --> 00:07:25.759 special flags, letters and figs that are used to switch 109 00:07:25.800 --> 00:07:29.079 between the two characters sets, and that doubles the amount 110 00:07:29.120 --> 00:07:32.920 of characters that can be sent. So there's a special 111 00:07:33.000 --> 00:07:35.439 character as a guy sending letters or numbers or something. 112 00:07:35.480 --> 00:07:38.160 You can set it and you get you know, you 113 00:07:38.160 --> 00:07:41.680 don't increase your your your five bits don't have to 114 00:07:41.680 --> 00:07:45.959 get bigger. Difference between mark and space tones is called 115 00:07:45.959 --> 00:07:51.120 the signal shift rtt Y. Usually that's at one hundred 116 00:07:51.120 --> 00:07:54.040 and seventy hertz. It's most common. It's not a rule, 117 00:07:54.079 --> 00:07:58.240 but that's what just better Buy uses. PSK thirty one 118 00:07:58.399 --> 00:08:02.120 is another mode. It's probably the most popular face shift 119 00:08:02.279 --> 00:08:05.720 key mode. It's called thirty one BOD by some people 120 00:08:06.240 --> 00:08:09.199 US as a sound card to generate the the rtt 121 00:08:09.399 --> 00:08:13.000 Y signals. Thirty one is the symbol rates Actually thirty 122 00:08:13.040 --> 00:08:16.800 one point twenty five bod designed for keyboard to keyboard 123 00:08:16.800 --> 00:08:21.199 communication typing at rates up the fifty words per minute. 124 00:08:21.279 --> 00:08:23.759 So that's fast enough for me because I couldn't type 125 00:08:23.759 --> 00:08:28.800 that fast and as referred to as BPSK thirty one 126 00:08:30.279 --> 00:08:35.399 QPSK since two audio tones, so there are now four 127 00:08:35.440 --> 00:08:42.000 possible phase combinations. Okay, so since PSK has two tones, 128 00:08:42.039 --> 00:08:44.960 you have to select the right sideband to the correct 129 00:08:45.000 --> 00:08:47.480 sideband here, either upper or lower. If you're in the 130 00:08:47.519 --> 00:08:50.279 wrong sideband, you're gonna you're gonna invert your tone, so 131 00:08:50.320 --> 00:08:53.200 you're not gonna decode it. So make sure you understand 132 00:08:53.240 --> 00:08:56.720 what band you're on. Usually it's upper sideband even no 133 00:08:56.720 --> 00:09:00.440 matter what band you're on for the for the digital modes, 134 00:09:00.919 --> 00:09:04.120 but if you're tuned in and you're not copying, swap 135 00:09:04.200 --> 00:09:07.200 sidebands and see if it starts reading correctly, so it 136 00:09:07.279 --> 00:09:13.639 is sideband sensitive. PSK uses a variable link character called 137 00:09:13.759 --> 00:09:16.600 very COODE that assigns shorter codes to common characters and 138 00:09:16.639 --> 00:09:21.039 longer codes for uncommon characters like Morse code, capital letters, 139 00:09:21.039 --> 00:09:24.200 and punctuation take longer decent if you're using If you're 140 00:09:24.279 --> 00:09:28.440 used to do RTTY with no lowercase, turn off caps 141 00:09:28.480 --> 00:09:31.960 lock because they take more. Something I didn't know for 142 00:09:32.000 --> 00:09:34.720 a while was I didn't know it was any different 143 00:09:34.879 --> 00:09:38.559 on you know, the character you sent, whether it's sent 144 00:09:39.559 --> 00:09:41.799 eight characters or three, was based on what you had tied. 145 00:09:41.840 --> 00:09:45.279 Good news. Really, I couldn't die types so slow. It 146 00:09:45.279 --> 00:09:48.159 didn't make any difference. But that's interesting fact there. So 147 00:09:48.279 --> 00:09:51.200 QPSK thirty one and PSK thirty one have about the 148 00:09:51.200 --> 00:09:55.720 same band with two point five killer hertz. QPSK is 149 00:09:55.759 --> 00:10:01.679 sideband sensitive and it's encoding provides error detection. So what's 150 00:10:01.720 --> 00:10:04.840 the most common frequency shift E mission on the amateur 151 00:10:04.960 --> 00:10:08.440 HF bands on the shift one hundred and seventy hertz 152 00:10:08.519 --> 00:10:11.279 number B letter B? Which of the following is characteristic 153 00:10:11.320 --> 00:10:18.039 of QPSK coding error corrections approximately the same? Sideband sensitive? 154 00:10:18.080 --> 00:10:20.840 I think all those sound right, that's correct. Which of 155 00:10:20.919 --> 00:10:25.519 the following describes a BOTTO code? It's a five big 156 00:10:25.639 --> 00:10:29.279 code at BC. Which of the following statements is true 157 00:10:29.279 --> 00:10:35.559 about PSK thirty one upp acase on use very coode 158 00:10:36.639 --> 00:10:40.639 b B with b B. Which type of code is 159 00:10:40.720 --> 00:10:44.559 used for sending characters in a PSK thirty one signal 160 00:10:46.519 --> 00:10:50.960 very code A? All right, talk about some packet based. 161 00:10:50.960 --> 00:10:55.440 These are structured modes and they're derived from early teletype 162 00:10:55.440 --> 00:10:59.480 over radio or computer to computer network systems. Hams have 163 00:10:59.519 --> 00:11:03.200 adapted the protocols creating packet radio, pack tool, win More 164 00:11:03.240 --> 00:11:07.840 and other communication systems. Some packet modes JT sixty five 165 00:11:07.879 --> 00:11:14.320 and FT eight require precisely defined transmission periods. The utility 166 00:11:14.360 --> 00:11:17.279 software is a able to keep your computer synchronized within 167 00:11:17.320 --> 00:11:19.960 one second of the standard time. So some of these 168 00:11:19.960 --> 00:11:22.919 modes like FT eight get you sixty five your your 169 00:11:22.919 --> 00:11:25.480 local time source is important to have it sync within 170 00:11:25.519 --> 00:11:29.679 a second of the guy you're talking to. So some 171 00:11:29.720 --> 00:11:33.080 of the basis of packet packet refers to the transmission 172 00:11:33.120 --> 00:11:41.360 of data and structured groups called frames. Packet communication systems 173 00:11:42.279 --> 00:11:45.039 package data with the package the data with control and 174 00:11:45.120 --> 00:11:48.480 routing information, and add error detection information. Each package or 175 00:11:49.159 --> 00:11:52.320 of header, data and trailers called the frame. Different packet 176 00:11:52.320 --> 00:11:56.480 protocols are used for different sets of information and mesags 177 00:11:56.519 --> 00:11:59.200 of creating the frame, but basically the same. You use 178 00:11:59.240 --> 00:12:00.799 to have a header the data, and you have some 179 00:12:00.879 --> 00:12:06.399 kind of trailers. The header contains the bit patterns that 180 00:12:06.399 --> 00:12:09.720 allow receivers to sync with the package structure, control of 181 00:12:09.759 --> 00:12:14.200 routing information in some then for some protocols, air detection 182 00:12:14.320 --> 00:12:18.240 correction data is the data is the data to exchange 183 00:12:18.240 --> 00:12:22.639 between the systems, usually asking characters, usually compressed for efficiency. 184 00:12:23.519 --> 00:12:26.320 The trailer vent is added on the information at the 185 00:12:26.440 --> 00:12:32.120 end for error detection. Forward error correction goes beyond simply 186 00:12:32.159 --> 00:12:36.399 detecting errors. By including redundant encoded info with the data, 187 00:12:36.519 --> 00:12:40.720 it's possible for receiver to correct certain types of data errors. 188 00:12:42.159 --> 00:12:46.000 Most common air detection mechanism is called a cyclic redundancy 189 00:12:46.080 --> 00:12:53.559 check or CRC. On an ARQ system, automatic repeat requests. 190 00:12:53.679 --> 00:12:58.159 If mismatched is detected, the receiving system responds with the knack, 191 00:12:58.240 --> 00:13:02.919 which not acknowledged and the proto the protocol request retransmission 192 00:13:03.799 --> 00:13:07.480 transmitting will continue to send. The transmitting system will continue 193 00:13:07.519 --> 00:13:10.840 to send pack it until it's received without air or 194 00:13:10.919 --> 00:13:18.000 retransmissions has reached a limit okay. ARQ is used in packtor, 195 00:13:18.279 --> 00:13:23.759 packet radio, and win more. ARQ protocols were used for 196 00:13:23.879 --> 00:13:27.159 wired network connections and the transmission can only be received 197 00:13:27.159 --> 00:13:30.480 from one receiving station during the connection. This means you 198 00:13:30.519 --> 00:13:34.200 can't break into a contact between two stations using ARQ. 199 00:13:34.480 --> 00:13:39.039 So if Jason and I are talking ARQ. Our systems 200 00:13:39.080 --> 00:13:41.039 are trying to talk to each other. If somebody else 201 00:13:41.440 --> 00:13:43.080 gets in there, we're not going to respond to them 202 00:13:43.120 --> 00:13:46.600 because we're trying to complete our handshakes. So that's what 203 00:13:46.600 --> 00:13:49.919 they're talking about here. You can't break If two stations 204 00:13:49.919 --> 00:13:51.799 are talking, don't try to break into them because you're 205 00:13:51.799 --> 00:13:53.080 not going to be acknowledged and you're just going to 206 00:13:53.159 --> 00:13:55.600 cause interference on what they're trying to do. So that 207 00:13:55.639 --> 00:13:58.919 a station can advertise as presence, however, ARQ protocols provide 208 00:13:58.919 --> 00:14:02.080 a broadcast mode to trans meant without another station having 209 00:14:02.080 --> 00:14:07.639 to established consonants UH contact, So so you can there's 210 00:14:07.679 --> 00:14:09.320 a there's a there's a mode where you just like 211 00:14:09.360 --> 00:14:11.559 calling c Q and a ar Q and if somebody 212 00:14:11.559 --> 00:14:13.759 here's it, their station will respond on the two view 213 00:14:13.799 --> 00:14:17.120 will pair up. I used to do this long time 214 00:14:17.159 --> 00:14:23.039 ago amp uh app's the app core UH long am 215 00:14:23.200 --> 00:14:27.799 I forgot what it's called long time ago. A mod 216 00:14:27.840 --> 00:14:30.440 mode is also provided so that stations can listen to 217 00:14:30.480 --> 00:14:33.840 the other stations without getting into their error correction scheme right. 218 00:14:35.279 --> 00:14:37.200 Using the moond mode allows you to determine if the 219 00:14:37.200 --> 00:14:39.759 frequency is occupied by two stations having an a ar 220 00:14:39.799 --> 00:14:43.320 Q mode contact. It's designed to transfer data between only 221 00:14:43.360 --> 00:14:46.399 two stations, mean that you can't break into the contact. 222 00:14:46.519 --> 00:14:52.840 Talked about that packet radio t R system developed to 223 00:14:53.240 --> 00:14:57.399 compensate for transmission errors and r t t Y used 224 00:14:57.399 --> 00:15:03.080 almost exclusively on the UHF bands, packet radios and shorts 225 00:15:03.080 --> 00:15:06.600 bursts of characters with error detection and correction data. It's 226 00:15:06.679 --> 00:15:11.120 based on computer network protocols x DOT two five, one 227 00:15:11.120 --> 00:15:15.279 of the oldest packet switching communications protocols popular during the 228 00:15:15.320 --> 00:15:18.679 late nineteen seventies and eighties. Back when I was learning 229 00:15:18.720 --> 00:15:21.240 about stuff that was that was slick stuff. Back in 230 00:15:21.279 --> 00:15:26.039 the day, packets exchange using VHF FM voice at twelve 231 00:15:26.120 --> 00:15:32.440 hundred and ninety six hundred BOB. Today we've got we've 232 00:15:32.440 --> 00:15:36.039 got some improvements over that. It does not work well 233 00:15:36.080 --> 00:15:39.840 with HF broadcasts because of the noise and fading and 234 00:15:40.120 --> 00:15:42.080 AHF you to have to be at three hundred bar 235 00:15:42.559 --> 00:15:49.159 or lower. HF UHF packets still big around here, works 236 00:15:49.159 --> 00:15:57.759 works good day. Pactor and win More so these reliably, 237 00:15:57.919 --> 00:16:00.799 I mean the rival they're kind of low, but they're 238 00:16:00.879 --> 00:16:04.279 reliable and they're robust. Packed tour is packet based to 239 00:16:04.360 --> 00:16:08.279 you are win More's win based to you are they 240 00:16:08.360 --> 00:16:12.639 work pretty well. Packed Tour one uses frequency shift King modulation. 241 00:16:12.879 --> 00:16:16.000 Packed Tour one through four use advanced PSK pack to 242 00:16:16.200 --> 00:16:21.399 four not yet legal for us amateurs, might be coming close. 243 00:16:21.480 --> 00:16:24.360 I mean there's there's legislation they're working on getting that, 244 00:16:24.440 --> 00:16:28.919 but it's a very good mode. They work fine. Pack 245 00:16:29.000 --> 00:16:32.039 Tor and Varro modes have overcome some of the issues 246 00:16:32.039 --> 00:16:35.879 with HF. I know, we use Vara on our packet 247 00:16:35.960 --> 00:16:40.320 system here. We do dual mode packet or the regular 248 00:16:41.240 --> 00:16:47.200 packet twelve twelve hundred bod. Varro works well and seems 249 00:16:47.200 --> 00:16:50.360 to be doing good round here. Okay. Win Link so 250 00:16:50.440 --> 00:16:53.480 win Link is a is a way to transfer email 251 00:16:53.519 --> 00:17:00.240 and messaging over HF. We use it VHF UHF here 252 00:17:00.279 --> 00:17:06.000 also for our areas work and it's a well established group. 253 00:17:06.119 --> 00:17:12.160 We've got several wind Link ports here in town and 254 00:17:12.680 --> 00:17:16.000 they work very well. And wind Link isn't a mode, 255 00:17:16.039 --> 00:17:21.519 it's a gateway communications system. It uses the Internet to 256 00:17:21.559 --> 00:17:25.119 connect it's email services with a gateway and mailbox stations 257 00:17:25.119 --> 00:17:29.960 around the world on HF. VHF and UHF said it's 258 00:17:30.039 --> 00:17:32.119 been around the wild, it's been improved a lot, and 259 00:17:32.160 --> 00:17:36.279 it's fairly reliable and all those fails. It's a good 260 00:17:36.279 --> 00:17:39.240 mode to get stuff going. Win Link stations did not 261 00:17:39.279 --> 00:17:41.839 connect directly to the Internet, but they provide a means 262 00:17:41.839 --> 00:17:45.039 for stations out of your local Internet coverage to connect 263 00:17:45.200 --> 00:17:49.720 in range. So that's pretty cool. If you have a 264 00:17:49.759 --> 00:17:54.279 regional outage somewhere, power data, fiber, oppet cables cut, no 265 00:17:54.359 --> 00:17:58.799 Internet allows you to connect RF to someone plays else 266 00:17:58.799 --> 00:18:01.160 that does have Internet connection. You can get your email 267 00:18:01.240 --> 00:18:06.119 and your data truth so even without Internet connectivity. Win 268 00:18:06.200 --> 00:18:10.400 Link Express, which is a program you can download, runs 269 00:18:10.440 --> 00:18:14.160 in a PC, can act as a standalone mailbox station 270 00:18:14.480 --> 00:18:17.880 or communicate directly with each other. You can do peer 271 00:18:17.880 --> 00:18:21.119 to peer connections. Done all that so on HF. Win 272 00:18:21.200 --> 00:18:25.119 Link uses pack Tour and Vara modes. Uh Var is 273 00:18:25.119 --> 00:18:30.960 the most popular, is the more popular. Vara is a 274 00:18:31.119 --> 00:18:35.720 tour software developed by e A five HBK software, So 275 00:18:36.799 --> 00:18:41.480 check that out. Okay, FT eight and whisper. These are 276 00:18:41.519 --> 00:18:45.839 called Wheat signal modes. They're supported by the WSJT software suite. 277 00:18:47.079 --> 00:18:52.200 A lot of cool modes in there. Here's a you 278 00:18:52.240 --> 00:18:54.480 can go check it out that They use eight tone, 279 00:18:54.559 --> 00:18:58.720 frequency shift, king modulation and air decoding. Correction to enable 280 00:18:58.759 --> 00:19:03.880 successful decoding. Very low signal to noise ratios. FT eight's 281 00:19:03.960 --> 00:19:08.480 and seventy five bit messages limits messages to call signs, 282 00:19:08.559 --> 00:19:13.400 good locations and signal reports only. FT eight signal reports 283 00:19:13.440 --> 00:19:15.880 are on the signal deloise ratio, so a report of 284 00:19:15.920 --> 00:19:18.359 plus three means the signal was three dB above the 285 00:19:18.400 --> 00:19:22.759 noise floor. We's com in FT eight. Transmission ranges are 286 00:19:22.759 --> 00:19:27.160 in fourteen seven four to fourteen seven seven. Be sure 287 00:19:27.160 --> 00:19:30.359 to locate a clear frequency and selected timeslot that doesn't 288 00:19:30.359 --> 00:19:34.319 interfere with the calling stations. Specifically when responding the clear 289 00:19:34.400 --> 00:19:38.720 frequency and the ultimate time slot so that used by 290 00:19:38.799 --> 00:19:42.920 the calling station. So FD eight's very popular. Done a 291 00:19:43.000 --> 00:19:47.920 lot of that that myself. It's a lot of fun Whisper. 292 00:19:50.079 --> 00:19:53.039 It's an HF propagation passed the week signal things. I 293 00:19:53.160 --> 00:19:56.640 run two Whisper notes from my home on thirty and 294 00:19:56.880 --> 00:20:01.200 twenty meters all the time. It doesn't support two way QSOs, 295 00:20:01.319 --> 00:20:04.200 but I have a beacon that transmits and all the time, 296 00:20:04.240 --> 00:20:05.960 and I can go look at signal reports and see 297 00:20:05.960 --> 00:20:09.759 who's seen my signal around the country. Spun built the 298 00:20:09.759 --> 00:20:12.920 Whisper nodes myself. Fairly easy to do, and it's fun 299 00:20:12.920 --> 00:20:18.200 to play with. Okay, low power Whisper transmitters generate coded packets. 300 00:20:18.240 --> 00:20:21.200 Stations that receive these reports can report them on the 301 00:20:21.240 --> 00:20:23.839 whispernet dot org and it's fun to go look at 302 00:20:23.839 --> 00:20:29.880 your signal reports and see what you can see. So okay, 303 00:20:30.000 --> 00:20:35.240 amateur wireless networks certain wireless networks. When networking frequencies overlap 304 00:20:35.319 --> 00:20:38.559 with amateur bands, amateurs are able to use them for 305 00:20:38.640 --> 00:20:41.160 many of the same purposes that under license users are 306 00:20:41.200 --> 00:20:45.079 able to, such as text messages, voice over IP, email, 307 00:20:45.119 --> 00:20:48.759 et cetera. If you operate a wireless network on FCC 308 00:20:48.799 --> 00:20:51.920 Part ninety seven frequencies, you must comply with the prohibit 309 00:20:52.079 --> 00:20:57.079 the prohibitions on encryption. HAM used two basic network topologies, 310 00:20:57.200 --> 00:21:00.599 Mesh and Star configurations, and advantage of the met network 311 00:21:00.599 --> 00:21:03.880 prot topology is that if one node fails, the packet 312 00:21:03.880 --> 00:21:06.359 may be able to find this destination by routing through 313 00:21:06.759 --> 00:21:14.200 another available node. So here's some wireless network frequencies that 314 00:21:14.200 --> 00:21:18.920 that we have that we can share and use. And 315 00:21:18.920 --> 00:21:22.480 in these bands, there are some HAM specific channels that 316 00:21:22.960 --> 00:21:27.519 are on our side, which really makes it nice. Arden 317 00:21:27.599 --> 00:21:31.279 is an amateur radio emergency data network. It's a mesh 318 00:21:31.319 --> 00:21:35.720 network can be made uses commercially available routers and the 319 00:21:35.920 --> 00:21:38.000 nine hundred two point four two point four five point 320 00:21:38.000 --> 00:21:43.039 eight giggers band Arden website one of the best websites 321 00:21:43.079 --> 00:21:46.440 I've seen for information and how to understand and get information. 322 00:21:46.559 --> 00:21:48.519 They do a great job. There's a go to the 323 00:21:48.559 --> 00:21:52.200 ardmesh dot org if you're inntioned in. That generally used 324 00:21:52.240 --> 00:21:55.400 during the emergency to support communication events like road races, 325 00:21:55.440 --> 00:21:58.680 parades and other large gatmies. But it uses that you 326 00:21:58.720 --> 00:22:02.759 can use the commercial items h put them into the 327 00:22:02.759 --> 00:22:07.799 handbands and they work. They weren't great, Let's see. It's 328 00:22:07.839 --> 00:22:14.319 a digital protocol users one link B. Which of the 329 00:22:14.319 --> 00:22:17.839 following is a good practice when using a transmittered frequency 330 00:22:18.279 --> 00:22:21.960 to answer a station calling CQ using FT eight UH, 331 00:22:22.079 --> 00:22:23.880 I think you want to call. You want to find 332 00:22:23.880 --> 00:22:27.240 a clear frequency during the same time slot as the 333 00:22:27.319 --> 00:22:30.480 calling UH and the ultimate timeslot as the calling stations 334 00:22:30.559 --> 00:22:33.880 that would be D. Which of the following is required 335 00:22:33.920 --> 00:22:38.759 when using FT eight You need a computer with accurate 336 00:22:38.799 --> 00:22:43.079 time within a one second. That's the key. B. How 337 00:22:43.079 --> 00:22:45.759 do you join a contact between two stations using the 338 00:22:45.799 --> 00:22:52.559 pack tool protocol UH? It is not possible see because uh, 339 00:22:52.960 --> 00:22:55.400 it's only limited to two stations, so see is it. 340 00:22:56.319 --> 00:22:58.920 What is the primary purpose of an amateur AIO data 341 00:22:58.920 --> 00:23:02.359 network mesh network. Let's c to provide high speed data 342 00:23:02.359 --> 00:23:07.839 services during emergency or a community event. Which of the 343 00:23:07.839 --> 00:23:11.519 following describes win Link. It's a wireless network capable of 344 00:23:11.559 --> 00:23:15.319 both VHF and HF band operation, form of packet radio 345 00:23:16.920 --> 00:23:20.640 and all those D. What is another name for a 346 00:23:20.720 --> 00:23:25.920 win link remote message server. It's called the gateway. Which 347 00:23:25.960 --> 00:23:29.039 of the following is a common location for FT eight. 348 00:23:30.200 --> 00:23:33.400 It's between fourteen oh seventy four and fourteen oh seventy 349 00:23:33.440 --> 00:23:38.400 seven C. What type of modulation is used by FT eight? 350 00:23:38.799 --> 00:23:42.960 It uses eight tone frequency shift key. Hey, what is 351 00:23:43.079 --> 00:23:51.920 QPSK modulation? It's modulation using let's see the angles, degrees, 352 00:23:51.960 --> 00:23:56.200 face shifts at the bottom. D. Which digital mode is 353 00:23:56.279 --> 00:23:59.400 used as a low power beacon for assessing HF propagation 354 00:24:00.119 --> 00:24:05.160 be a whisper node weak signal propagation. What part of 355 00:24:05.279 --> 00:24:09.400 packet radio frame contains the routing and handling information? That's 356 00:24:09.440 --> 00:24:15.880 the preamble. Excuse me, sorry, it's the header. The header 357 00:24:15.920 --> 00:24:20.400 has the UH. The information contained a routing handling information? 358 00:24:20.440 --> 00:24:25.240 Sorry about that? The header in an an ARQ mode. 359 00:24:25.279 --> 00:24:27.960 What is meant by NAC response to a transmitted packet? 360 00:24:29.640 --> 00:24:33.440 It means how does forward error correction allow the receiver 361 00:24:33.519 --> 00:24:39.200 to correct data errors by transmitting or doneant information? See 362 00:24:40.519 --> 00:24:43.559 what does an FD eight signal report of three plus 363 00:24:43.839 --> 00:24:46.160 three plus three means? That means it's three times the 364 00:24:46.160 --> 00:24:53.519 noise level? Yep, all right. Most digital modes on HF 365 00:24:53.519 --> 00:24:57.400 are transmitted as USB signals, the exception as rtt Y 366 00:24:57.640 --> 00:25:02.400 uses LSB modem and software must be configured for the 367 00:25:02.400 --> 00:25:06.680 correct moder rate receiving tone received data signal screen you 368 00:25:06.720 --> 00:25:10.680 know to be tuned correctly. Since PSK uses a single tone, 369 00:25:10.759 --> 00:25:17.200 either USB or LSB will work. Most use USB. Like 370 00:25:17.279 --> 00:25:20.599 other amateur signals. Digital mode bandwidth is defined by the FCC. 371 00:25:21.519 --> 00:25:24.680 The bandwidth of signal changes with symbol rate. The symbol 372 00:25:24.759 --> 00:25:28.200 rate increases, so does the bandwidth needed for the signal 373 00:25:28.480 --> 00:25:33.000 needed to transmit them. Most common method of generating transmitting 374 00:25:33.519 --> 00:25:35.759 these modes is to connect to an audio output of 375 00:25:35.759 --> 00:25:39.039 a computer sound card to the microphone of a single 376 00:25:39.039 --> 00:25:42.000 sideband transceiver. So most time you're going to use your 377 00:25:42.039 --> 00:25:45.279 computer to connect the sound card connect the tune radio. 378 00:25:45.640 --> 00:25:47.920 Here's a chart that shows some of the bandwidths of 379 00:25:49.480 --> 00:25:52.960 the different digital modes. What's interesting to point out here 380 00:25:53.000 --> 00:25:56.640 is like PSK thirty one and FT eight, they're fifty hertz. 381 00:25:56.680 --> 00:25:59.559 Why we don't send a lot of information there, but 382 00:25:59.559 --> 00:26:02.759 they're fifty hurts wide, so that means you could put 383 00:26:03.799 --> 00:26:11.599 fifty uh QSOs fifty times five. It's twenty five hundred 384 00:26:11.799 --> 00:26:15.519 in a you need some space, but you can put 385 00:26:15.640 --> 00:26:20.480 a bunch in a audio passband right. So sometimes you'll 386 00:26:20.519 --> 00:26:24.079 see in the FT eight modes just the whole past 387 00:26:24.119 --> 00:26:25.799 base is loaded, we'll sleep, so you can get a 388 00:26:25.839 --> 00:26:30.839 lot of QSOs in one. It's very efficient five percent 389 00:26:30.880 --> 00:26:34.960 of the time. But FM modes and these digital modes, 390 00:26:35.039 --> 00:26:38.720 you're transmitting full power the whole time that you're transmitting, 391 00:26:38.759 --> 00:26:40.799 and those times those can be you know, several seconds 392 00:26:40.839 --> 00:26:43.519 to half amended or something, so you have to be 393 00:26:43.559 --> 00:26:46.720 real careful. Make sure you watch your transmitter, don't ex seed. 394 00:26:46.720 --> 00:26:50.279 It's average power rating, so reduce the transmit power to 395 00:26:50.279 --> 00:26:52.880 prevent overheating. Usually I buy about fifty percent is usually 396 00:26:52.880 --> 00:26:58.559 a good idea. Digital modes can generate interference, just like 397 00:26:58.680 --> 00:27:02.400 phone and c W. For digital modes that use a 398 00:27:02.400 --> 00:27:07.920 single sideband transmitter to transmit audio FSK. Most common problem 399 00:27:07.960 --> 00:27:10.039 is supplying too much or too little audio from the 400 00:27:10.079 --> 00:27:14.400 computer to the radio's microphonium pit a waterfall display. The 401 00:27:14.480 --> 00:27:18.559 vertical lines represent spurrac emissions caused by overmodulation of the transmitter. 402 00:27:19.920 --> 00:27:24.519 ALC and digital modes Automatic level control are their use 403 00:27:24.759 --> 00:27:29.680 for preventing excessive drive to the amplifier inputs. ALC circuit 404 00:27:29.680 --> 00:27:32.960 produces gain when power level gets too high. However, it 405 00:27:32.960 --> 00:27:35.720 comes at a price. The signal compression can result in 406 00:27:35.799 --> 00:27:42.039 distortion resist temptation to turn up gain. For digital signals, 407 00:27:42.079 --> 00:27:45.160 distortion caused by ALC makes the signal harder to decode 408 00:27:45.480 --> 00:27:51.960 create spurase emissions. It's similar to overmodulation. When in digital mode, 409 00:27:52.039 --> 00:27:55.160 your ALC system should be either disabled or input level 410 00:27:55.200 --> 00:27:56.920 and gain turned down to the point where the ALC 411 00:27:57.079 --> 00:28:01.880 does not activate. So my experience operating this is or 412 00:28:02.000 --> 00:28:03.759 any of the digital mode. This is probably the most 413 00:28:03.880 --> 00:28:08.599 common airror mistake misunderstood piece by some new opera by 414 00:28:08.640 --> 00:28:12.599 operators they don't have their ALC their audio input adjusted right. 415 00:28:14.079 --> 00:28:16.240 You can turn it off. But what I do is 416 00:28:16.240 --> 00:28:18.720 I have mine turned on, but I have it right 417 00:28:18.759 --> 00:28:21.119 below where it cuts on like it, just like it says, 418 00:28:21.160 --> 00:28:23.880 so that seems to be the right sweet spot for me. 419 00:28:24.000 --> 00:28:26.960 But you can hear you can see a station when 420 00:28:27.000 --> 00:28:29.960 they're really over modulating their signal, their call sign will 421 00:28:30.000 --> 00:28:32.480 show up four times in the FT eight pass band, right, 422 00:28:32.559 --> 00:28:36.039 So this is probably the most important thing to go 423 00:28:36.640 --> 00:28:39.319 adjust and correct is get your audio levels right coming 424 00:28:39.359 --> 00:28:42.319 from your from from your PC. If you're using a 425 00:28:42.319 --> 00:28:47.039 Windows thing, Windows sometimes does favorite things to your sound 426 00:28:47.119 --> 00:28:50.519 card when you didn't want it to an update or something, 427 00:28:50.640 --> 00:28:52.559 so always check this and make sure you got an 428 00:28:52.559 --> 00:28:56.119 eye on. I always have my my ALC meter up 429 00:28:56.599 --> 00:28:59.440 on my so I can always see if something's going 430 00:28:59.480 --> 00:29:02.319 on there. ALC is a big is a big deal 431 00:29:02.400 --> 00:29:06.440 in digital modes, all right. It's send to some practice 432 00:29:06.519 --> 00:29:10.960 questions which mode is normally used when sending rtt Y signals. 433 00:29:11.480 --> 00:29:14.440 So rtt Y is almost always doing in lower sideband, 434 00:29:16.759 --> 00:29:19.599 and for the all the other digital modes it's usually 435 00:29:19.680 --> 00:29:24.720 upper sideband, which is bu What could be wrong if 436 00:29:24.720 --> 00:29:27.880 you cannot decode an RTTY or other FSK signal even 437 00:29:27.920 --> 00:29:32.240 though it apparently tuned in properly. Market space can be 438 00:29:32.279 --> 00:29:35.799 reversed wrong boderate wrong side I think all those sound 439 00:29:35.839 --> 00:29:40.319 correct to me, and that is correct? What should the 440 00:29:40.359 --> 00:29:43.880 ALC system? Why should the ALC system be active when 441 00:29:43.880 --> 00:29:47.799 transmitting AFK signals? Too much ALC can cause a transmitter 442 00:29:48.079 --> 00:29:52.000 to I think it's B. The ALC can action can 443 00:29:52.039 --> 00:29:55.200 distort the signal. Why is it important to know the 444 00:29:55.319 --> 00:30:00.200 duty cycle of the mode you're using when transmitting? Want 445 00:30:00.200 --> 00:30:02.920 to make sure you don't exceed your transmitter's average power 446 00:30:03.000 --> 00:30:07.720 rating or can be B. What is the relationship between 447 00:30:07.799 --> 00:30:12.480 transmitted symbol rate and bandwidth? Uh? The higher symbol rates 448 00:30:12.519 --> 00:30:17.920 require wider bandwidth, so that's B. What is indicated on 449 00:30:17.960 --> 00:30:20.519 a waterfall display by one or more vertical lines on 450 00:30:20.559 --> 00:30:22.359 either side of the data mode on an r TTU 451 00:30:22.400 --> 00:30:30.599 I signal, usually that's over modulation. Okay, let's talk about 452 00:30:31.519 --> 00:30:35.119 in a digital mode. How do we initiate a contact? Right? So, yeah, 453 00:30:35.400 --> 00:30:38.519 like a voice mode, You type in C Q c Q, 454 00:30:38.839 --> 00:30:41.759 this is my case, K M four CJ, save it 455 00:30:41.799 --> 00:30:45.319 a few times, put a K at the end saying hey, 456 00:30:45.640 --> 00:30:49.680 I'm waiting for someone to contact me that I'm over, 457 00:30:49.839 --> 00:30:54.000 and then the response station would say my call sign. 458 00:30:54.519 --> 00:30:57.920 This is followed by the answering station's call signed with 459 00:30:57.960 --> 00:31:01.920 the K at the end. Modes such as pactor and 460 00:31:02.000 --> 00:31:06.920 VARA the software mode and will have a specific disconnect message. 461 00:31:07.279 --> 00:31:09.799 But notice the K here to use at the end 462 00:31:09.799 --> 00:31:12.279 of a transmission to indicate the other station is to 463 00:31:12.319 --> 00:31:15.480 transmit as shown, so that says that I'm finished waiting 464 00:31:15.519 --> 00:31:21.319 on you. Right. It's like over if you connect to 465 00:31:21.319 --> 00:31:24.079 a gateway. The exact way you connect to the gateway 466 00:31:24.119 --> 00:31:26.359 depends on the equipment and the mode that you're using, 467 00:31:26.759 --> 00:31:29.119 but us it begins with some kind of a connect message. 468 00:31:29.680 --> 00:31:32.920 If the signal is received without air, there's usually a 469 00:31:34.000 --> 00:31:37.039 handshaking or right. They call it training sequence and packets 470 00:31:37.200 --> 00:31:40.119 to help for the two stations to determine the right 471 00:31:40.359 --> 00:31:44.920 road the VOD in the protocol to use. Because these 472 00:31:44.920 --> 00:31:48.759 stations respond without a human control operator they are operating. 473 00:31:48.799 --> 00:31:51.359 A lot of them are automatically run, so they have 474 00:31:51.440 --> 00:31:55.400 to fall under the rules of the digitally controlled Automatically 475 00:31:55.480 --> 00:31:59.400 Digitally controlled station rules, which restricts them to certain parts 476 00:31:59.400 --> 00:32:05.119 of the band and stations under FCC rules must operate 477 00:32:05.200 --> 00:32:08.920 under local remote control with control operator in charge of 478 00:32:08.960 --> 00:32:12.559 all transmissions. That's the rule. Here's where you can find 479 00:32:12.720 --> 00:32:17.440 on the band plan these automatically controlled digital stations are 480 00:32:17.480 --> 00:32:26.079 allowed to operate here. Then during the contole. A waterfall 481 00:32:26.200 --> 00:32:29.279 is kind of a neat display. It shows yours all 482 00:32:29.319 --> 00:32:33.599 the nearby signals. This is a PSK thirty one looks 483 00:32:33.640 --> 00:32:39.920 like The waterfall displays a series that shows the presence 484 00:32:39.960 --> 00:32:42.319 of signals and the series of lines representing the scan 485 00:32:42.440 --> 00:32:47.279 across the frequency range. Signal strengths is represented by brightness 486 00:32:47.480 --> 00:32:52.119 or density or color. As new lines are captured, older 487 00:32:52.119 --> 00:32:55.960 lines are removed as it moves down. The slides down 488 00:32:56.039 --> 00:33:00.079 the screen. It's called the waterfall tuning age for an 489 00:33:00.160 --> 00:33:03.440 RTTY signal. If I've got looking at an RTTY signal 490 00:33:03.440 --> 00:33:06.680 on a spectrum analyzer or or my audio spectrum analyzer, 491 00:33:07.319 --> 00:33:10.440 the vertical lines are the mark and the space. Uh 492 00:33:11.039 --> 00:33:15.240 those are these lines right here and help tune in, 493 00:33:15.359 --> 00:33:17.319 so you would tune across the band. You're going to 494 00:33:17.400 --> 00:33:20.759 line up your as you move this wiggly line across 495 00:33:20.759 --> 00:33:22.720 you want to line them up to these right here 496 00:33:23.480 --> 00:33:27.920 and helps you tune in the signal. There's a also 497 00:33:28.519 --> 00:33:33.000 you can look on a silloscope kind of thing and 498 00:33:33.039 --> 00:33:37.240 see the crossed ellipse from the right. They're used to 499 00:33:37.240 --> 00:33:39.640 to see how well fine tuned if you're perfectly tuned, 500 00:33:39.680 --> 00:33:43.359 you'll see two ellipses perfectly at ninety degrees angles. That 501 00:33:43.480 --> 00:33:45.559 indicates how good your tuning is going. That's a pretty 502 00:33:45.559 --> 00:33:50.160 good looking signal there. Okay. Third party traffic. All the 503 00:33:50.240 --> 00:33:53.960 rules about third party traffic apply to digital transmissions. You know. 504 00:33:54.079 --> 00:33:57.200 That includes the information and the emails, the digital messages. 505 00:33:57.559 --> 00:34:00.000 If you transmitter a web page or whatever kind of thing, 506 00:34:00.039 --> 00:34:04.200 third party rules still apply. Commercial messages may not be 507 00:34:04.240 --> 00:34:09.960 transmitted via amateur radio, so interfering signals in digital modes 508 00:34:10.119 --> 00:34:12.360 hidden transmitters. If I'm talking to a guy over in 509 00:34:12.400 --> 00:34:15.519 Europe FT eight, I don't hear I don't. I only 510 00:34:15.559 --> 00:34:17.440 hear him, But over in Europe he may be hearing 511 00:34:17.480 --> 00:34:19.719 three or four guys on the same frequency I'm on, 512 00:34:20.239 --> 00:34:22.159 but I can't hear them, so I may have a 513 00:34:22.199 --> 00:34:24.360 hard time talking to him. So that's sort of what 514 00:34:24.400 --> 00:34:28.039 referred to as he's hidden to me. It's okay. The 515 00:34:28.119 --> 00:34:32.880 result is unintentional, but it prevents us from uh from 516 00:34:32.920 --> 00:34:36.719 completing the contact. Unpacket modes, packed tour or when more, 517 00:34:37.000 --> 00:34:42.239 they don't recover well from noisy and weak signal week environments, 518 00:34:42.920 --> 00:34:44.360 so you get a lot of failure If you get 519 00:34:44.360 --> 00:34:46.960 a lot of failure to connect or frequently tried after 520 00:34:46.960 --> 00:34:49.199 a long time, it may just be band conditions are 521 00:34:49.199 --> 00:34:51.800 too noisy, try a different band or something like that. 522 00:34:53.599 --> 00:34:58.119 So here's some practice questions for this section. What's required 523 00:34:58.480 --> 00:35:03.159 to conduct communications with the digital station operating automatic control 524 00:35:03.199 --> 00:35:08.400 outside the automatic control band segments, It's gonna be a 525 00:35:08.599 --> 00:35:10.519 the station is shame and the contact must be under 526 00:35:10.519 --> 00:35:14.400 local or remote control. Same rules that apply for voice 527 00:35:14.679 --> 00:35:18.159 for controlling the station UH with the automatic control. And 528 00:35:18.239 --> 00:35:22.440 what bands may automatically controlled stations transmit RTTY or data 529 00:35:22.480 --> 00:35:26.800 missions communicated with other controlled stations. I think only on 530 00:35:26.880 --> 00:35:32.159 the band's segment where it's permitted anywhere in the six 531 00:35:32.239 --> 00:35:34.519 meter or shorter wave. The bands are limited segments, that 532 00:35:34.599 --> 00:35:37.679 is corrected its specifically to on the six meter band 533 00:35:37.719 --> 00:35:41.639 on this particular one UH. These are automatically controlled stations 534 00:35:41.679 --> 00:35:45.559 transmitting rtt y. You know, two of them in only 535 00:35:45.559 --> 00:35:47.360 one place you can do it, that's the six meter band. 536 00:35:48.360 --> 00:35:51.360 What symptoms may result from the other signals interfering with 537 00:35:51.440 --> 00:35:58.239 the pactor or VARA transmission? What symptoms frequent retries, long pauses, 538 00:35:58.280 --> 00:36:03.440 failure to establish connection between those all those symptoms that 539 00:36:03.880 --> 00:36:06.800 we've got interfer in the signals. Okay, Which is the 540 00:36:06.840 --> 00:36:09.320 following is a way to establish contact with the digital 541 00:36:09.360 --> 00:36:13.320 messaging gateway system. Uh, you don't send EMO to the 542 00:36:13.320 --> 00:36:17.679 control operator transmits it's a connect message is how you 543 00:36:18.159 --> 00:36:20.159 It's how you try to connect to them. Be deep? 544 00:36:21.480 --> 00:36:24.719 What action results from a failure to exchange information due 545 00:36:24.719 --> 00:36:27.920 to excessive transmission attempts when using an ar Q mode? 546 00:36:31.119 --> 00:36:35.079 I think connection has dropped. That's correct, because they're gonna 547 00:36:35.079 --> 00:36:37.280 there's a time out time or you're gonna try to 548 00:36:37.280 --> 00:36:39.159 talk to somebody. If you're talking to them and somebody 549 00:36:39.159 --> 00:36:42.039 you lose connections, there's a number of retries and then 550 00:36:42.079 --> 00:36:45.800 it gives up. So that's that's that's me. Which of 551 00:36:45.880 --> 00:36:50.400 the following describes a waterfall display? Let's see frequency is 552 00:36:50.599 --> 00:37:00.320 uh is vertical, amplitude is horizontal signal strength Uh, let's 553 00:37:00.320 --> 00:37:05.599 see signal strength time the C frequency spour is horizontal 554 00:37:05.639 --> 00:37:11.559 signal strength tensity. It is all vertic. Right, And that's 555 00:37:11.559 --> 00:37:19.159 the end of this chapter. M So you want to 556 00:37:19.320 --> 00:37:21.599 do another module? You want to stop for today? It's 557 00:37:21.639 --> 00:37:23.920 not loud and here, yeah, I think it is loud. Guy, 558 00:37:24.239 --> 00:37:29.719 that sounds good. I'm Okay, so that was the Okay, 559 00:37:29.719 --> 00:37:32.079 Our next topic we're going to talk about is UH. 560 00:37:32.719 --> 00:37:39.440 Here is dipoles, ground planes and yaggy antennas. The most 561 00:37:39.480 --> 00:37:44.039 fundamental antenna we have in AMATE radio is a dipole UH. 562 00:37:44.639 --> 00:37:48.599 It's a straight conductor that's half wave linked UH along 563 00:37:48.719 --> 00:37:51.239 with the feed point in the middle. It's also known 564 00:37:51.280 --> 00:37:55.760 as a double it antenna UH. The strongest radiation direction 565 00:37:55.920 --> 00:37:59.360 of the dipole's broadside to its axis and a plane 566 00:37:59.360 --> 00:38:03.000 containing the ant and its conductor. The weakest radiation is 567 00:38:03.000 --> 00:38:07.039 off the ends. The shape of asthmith pattern for a 568 00:38:07.079 --> 00:38:09.760 dipole and free space is shown in the next figure. 569 00:38:09.800 --> 00:38:11.440 And I'll show you here's the picture. This is what 570 00:38:11.440 --> 00:38:14.719 it looks like. Again. You've got a halfway link piece 571 00:38:14.719 --> 00:38:17.000 of wire feeding it in the center, stretched out for 572 00:38:17.599 --> 00:38:20.239 horizontally and this is the radiation patterns you can see. 573 00:38:20.280 --> 00:38:26.320 It has a radiation pattern broadside and to the back 574 00:38:26.880 --> 00:38:33.199 with a less radiation to the sides. So very fundamental antenna. 575 00:38:33.280 --> 00:38:36.559 Great antenna probably the most popular type of antenna we 576 00:38:36.599 --> 00:38:43.039 have to using in the HF bands. Okay. Diepole is 577 00:38:43.079 --> 00:38:47.079 often used as a reference antenna for gain measurements. Gain 578 00:38:47.199 --> 00:38:53.639 is measured in DBD. Isotropic antenna is a reference antenna 579 00:38:53.679 --> 00:38:57.800 with a gain given in dbi. The isotropic antenna is 580 00:38:57.800 --> 00:39:01.360 a theoretical antenna. It's an a tenda that radiates equally 581 00:39:01.360 --> 00:39:06.239 in all directions. So sometimes you'll see U an antenna 582 00:39:06.960 --> 00:39:10.760 the performance reference to dB I or just dB with 583 00:39:10.840 --> 00:39:13.480 the gains. So there's a way to convert between the two. 584 00:39:14.239 --> 00:39:18.360 To convert from dB D which is dB dipole the 585 00:39:18.480 --> 00:39:21.239 dB I, which is isotrophic, as you add two point 586 00:39:21.280 --> 00:39:25.079 one five dB h to convert dB I to dB 587 00:39:25.239 --> 00:39:30.960 D uses to subtract two point one five dB. Current 588 00:39:31.079 --> 00:39:34.199 in a halfway dipole is highest in the middle, that 589 00:39:34.320 --> 00:39:37.639 is in zero at the ends. Voltage along the dipole 590 00:39:38.239 --> 00:39:40.239 is highest at the ends and lowest in the middle. 591 00:39:40.280 --> 00:39:44.039 So if you have a dipole antenna, just remember that 592 00:39:44.039 --> 00:39:46.920 that the current is the highest in the middle, voltage 593 00:39:47.000 --> 00:39:48.840 is in lowest in the ends, and the and the 594 00:39:48.920 --> 00:39:55.280 voltage is the opposite. The halfway diepole, as we see 595 00:39:55.280 --> 00:39:58.880 here in this figure, has its maximum current at the 596 00:39:58.920 --> 00:40:02.840 middle U and the maximum excuse me has a minute. 597 00:40:02.840 --> 00:40:04.559 It has a maximum current in the middle of maximum 598 00:40:04.599 --> 00:40:09.199 bolted at the end. The feed point impedance is lowest 599 00:40:09.239 --> 00:40:13.719 in the middle. The odd harmonics of the fundamental frequency 600 00:40:14.000 --> 00:40:17.159 of the dipold speed point impediance is low at the midpoint. 601 00:40:17.400 --> 00:40:22.079 Once again has shown So if you've got harmonics, this 602 00:40:22.159 --> 00:40:24.119 is what they would look like based on if it's 603 00:40:24.119 --> 00:40:30.280 a half, if it's a second, third, fourth harmonic. So 604 00:40:30.599 --> 00:40:33.320 again the impedance is lowest in the middle for us 605 00:40:33.360 --> 00:40:37.679 for the this dipole, and typically dipoles about sixty eight 606 00:40:37.840 --> 00:40:44.119 sixty two homes. The impedance increases as a feed point 607 00:40:44.199 --> 00:40:47.679 is moved away from the center several thousand homes at 608 00:40:47.679 --> 00:40:52.400 the end. Popular antennas are in FED halfway off center, 609 00:40:52.400 --> 00:40:54.239 FED halfway. You'll hear a lot of those. Those are 610 00:40:54.239 --> 00:40:57.719 different variations of where you feed the end the antenna. 611 00:40:59.719 --> 00:41:02.840 The FED as an example as popular for porta bowl operation. 612 00:41:03.239 --> 00:41:07.320 It's a lightweight, easy to install. It's a halfway dipole 613 00:41:07.360 --> 00:41:12.000 fed at one end. In free space. The half wavelength 614 00:41:12.159 --> 00:41:14.559 is equal to about four hundred and ninety two divided 615 00:41:14.559 --> 00:41:18.199 by the frequency in megahertz. This is if you want 616 00:41:18.199 --> 00:41:21.920 to get the linked and feet you'll generally find that 617 00:41:22.199 --> 00:41:25.639 the length will be shorter than the free space wavelength. 618 00:41:25.760 --> 00:41:29.800 Calculation However, for these exam questions you don't have to 619 00:41:30.559 --> 00:41:33.480 take that into account. Just be aware that where thickness 620 00:41:33.480 --> 00:41:40.239 and hightabo bround influenced the resonant length and the length 621 00:41:40.239 --> 00:41:43.639 again in feet four hundred and ninety two divided by 622 00:41:43.639 --> 00:41:48.840 the frequency and wavelength. So what is the proximate length 623 00:41:48.920 --> 00:41:51.800 of in feet of a halfwave dipole resident of three 624 00:41:51.880 --> 00:41:54.840 point five to five megahurts? How would you calculate that? Well, 625 00:41:55.360 --> 00:41:57.320 remember we take our four hundred and ninety two divided 626 00:41:57.320 --> 00:41:59.280 by three point five to five and you get one 627 00:41:59.360 --> 00:42:02.960 hundred and thirty nine feet, So that would be the 628 00:42:02.960 --> 00:42:10.239 wavelength forty meters on eighty meters. Remember the axual antenna 629 00:42:10.280 --> 00:42:12.719 will be a little shorter than this, But build to 630 00:42:12.760 --> 00:42:15.280 that calculation and use your tuner to tell if it 631 00:42:15.320 --> 00:42:18.920 needs trimming. Ideally you won't. You want SWR as close 632 00:42:18.960 --> 00:42:23.119 to one to one as you can without tuning. So 633 00:42:23.119 --> 00:42:25.679 what's the approximate length and feet of a half wave 634 00:42:25.840 --> 00:42:28.519 dipole at fourteen point twenty five megahurts? This will be 635 00:42:28.519 --> 00:42:31.440 twenty meters, So remember to use your formula four ninety 636 00:42:31.440 --> 00:42:33.920 two divided by fourteen point twenty five and you get 637 00:42:34.079 --> 00:42:40.440 thirty four point five feet UH. Center fed dipoles are 638 00:42:40.480 --> 00:42:42.760 the easiest to use on the band which they are resident. 639 00:42:43.360 --> 00:42:46.119 The feed point impedance is a good match for a 640 00:42:46.159 --> 00:42:48.880 fifty or seventy five ONEm coax and for coacts on 641 00:42:48.920 --> 00:42:54.079 odd multiples of the fundamental frequency. A dipole doesn't need 642 00:42:54.119 --> 00:42:57.639 to be straight to be effective. Dipole can be supported 643 00:42:57.679 --> 00:43:01.039 in the center, where the feed line can be conveniently attached. 644 00:43:02.440 --> 00:43:05.440 There's another configuration called an inverted V, where you take 645 00:43:05.480 --> 00:43:09.039 the ends and lower them down. As long as the 646 00:43:09.119 --> 00:43:11.400 legs of the dipole form an angle of ninety degrees 647 00:43:11.519 --> 00:43:14.400 or more. The inverted V is nearly as effectively as 648 00:43:14.440 --> 00:43:20.199 a horizontal installed dipole. So how you fix your dipole, 649 00:43:20.280 --> 00:43:22.800 or how you based on the area that you've got 650 00:43:22.840 --> 00:43:24.559 to or the place you have to mount your antenna 651 00:43:24.679 --> 00:43:26.760 is going to determine a lot what's going to be 652 00:43:26.760 --> 00:43:29.519 the shape of your dipole. But don't worry too much 653 00:43:29.519 --> 00:43:32.639 about trying to keep it perfectly horizontally or you know, 654 00:43:32.960 --> 00:43:35.440 get your antenna up, tune it, get on the air. 655 00:43:36.719 --> 00:43:40.320 The ground plane antenna is one half of a dipole, 656 00:43:40.360 --> 00:43:43.480 with the missing portion made up by an electrical mirror 657 00:43:43.599 --> 00:43:47.960 or so we call that the ground plane. It's made 658 00:43:48.000 --> 00:43:52.840 from sheet metal or screen of the radios can be excused. 659 00:43:52.920 --> 00:43:55.239 The ground plane can be made from metal or a 660 00:43:55.280 --> 00:43:58.880 screen of radial wires. Basic ground plane is a quarterwave 661 00:43:58.960 --> 00:44:01.840 length long, with the feed point at the junction of 662 00:44:01.840 --> 00:44:04.920 the antenna and the ground plane. For HF ground playing 663 00:44:04.920 --> 00:44:07.400 antennas at ground level, radio wires are laid on the 664 00:44:07.400 --> 00:44:10.400 surface of the ground, or can be. They can't be 665 00:44:10.480 --> 00:44:16.000 buried within a few inches of the surface. Ground plays 666 00:44:16.039 --> 00:44:20.360 are called verticals because that's usually the way, uh that's 667 00:44:20.440 --> 00:44:22.840 usually the way they're constructed, and how you install them. 668 00:44:23.920 --> 00:44:27.559 A ground plane radiates the best broadside to its axis 669 00:44:28.719 --> 00:44:32.199 if installed vertically. The ground plane antenna pattern is omni directional, 670 00:44:32.800 --> 00:44:35.960 that is, its uniform in all asthmus angles or directions. 671 00:44:36.920 --> 00:44:41.320 Very useful for VHF and UHF mobile portable communications where 672 00:44:41.360 --> 00:44:44.480 the signals can maybe even where the signals they come 673 00:44:44.519 --> 00:44:50.679 from any direction. Here's a here's a picture of a 674 00:44:50.719 --> 00:44:54.400 ground play. Again. You've taken that diepole and you've made 675 00:44:54.800 --> 00:44:57.880 you've made it a quarterwavelength tall, and uh, you've taken 676 00:44:57.920 --> 00:44:59.800 the other half of the diepole you've made that your 677 00:45:00.320 --> 00:45:04.119 plane now. So the ground plane, whether made of solid 678 00:45:04.119 --> 00:45:07.519 metal or radio wires, creates an electrical mirror the image 679 00:45:07.519 --> 00:45:11.159 of the quarterwave antenna. This creates the electrical the electrical 680 00:45:11.159 --> 00:45:14.440 equivalent of a dipole antenna. The feed point impedance at 681 00:45:14.440 --> 00:45:16.719 the base of an ideal ground plane it's about thirty 682 00:45:16.760 --> 00:45:21.519 five omes half of a complete dipole's impedance. Because only 683 00:45:21.559 --> 00:45:24.360 half of the antenna is physically they're able to radiate 684 00:45:24.360 --> 00:45:28.280 the enter the energy. So remember the dipole center fed 685 00:45:28.320 --> 00:45:35.320 dipole is about sixty to sixty three ohs. The feed 686 00:45:35.360 --> 00:45:37.360 point and penants of a ground plane antenna with the 687 00:45:37.440 --> 00:45:42.239 radios perpendicular to the antenna proxy, thirty five omes resulting 688 00:45:42.239 --> 00:45:45.079 in a one point four to one SWR with a 689 00:45:45.159 --> 00:45:49.840 fifty oem coax fee. Drooping or sloping the radios gradually 690 00:45:50.280 --> 00:45:56.480 raises the feed point impedance until until the radios droops 691 00:45:56.559 --> 00:45:59.400 so far as to become only one half of the dipole. 692 00:45:59.440 --> 00:46:02.639 The feed point pediants becomes seventy two oms, so a 693 00:46:02.679 --> 00:46:06.599 fifty O feed point is reached with radios grouping approximately 694 00:46:06.679 --> 00:46:11.280 forty five degrees. These are real popular for vhf uhf. 695 00:46:11.280 --> 00:46:15.440 They're easy to make, and you just put your quarterway 696 00:46:15.639 --> 00:46:17.960 whatever your two meters or two twenty or four to 697 00:46:18.039 --> 00:46:21.559 forty and then do your ground radios and vend them 698 00:46:21.559 --> 00:46:24.320 slightly forty five degrees and they work great. You can 699 00:46:24.440 --> 00:46:26.599 put them in your in a closet in the attic 700 00:46:27.280 --> 00:46:32.119 and they're great antennas. Then a droop angle three to 701 00:46:32.159 --> 00:46:34.199 forty five degrees was shown in the last figure. It 702 00:46:34.199 --> 00:46:38.239 results in a feed point penance approximately cook approximing fifty oms. 703 00:46:38.800 --> 00:46:41.800 As with the dipole, it's not useful to provide a 704 00:46:41.880 --> 00:46:43.760 one size fits all formula for the length of the 705 00:46:43.800 --> 00:46:47.239 ground plane antenna. Since the ground plane is one half 706 00:46:47.280 --> 00:46:50.159 the size of a diepole. Start with one half the 707 00:46:50.159 --> 00:46:53.559 free space length and be prepared to trim the antenna's link. 708 00:46:53.639 --> 00:46:55.840 So you always want to start longer than you need 709 00:46:55.880 --> 00:46:59.320 because once you start trimming antenna sometimes it's difficult to 710 00:46:59.320 --> 00:47:03.760 go back the other way. So what's what's what's the 711 00:47:03.760 --> 00:47:07.880 approximate length and feet of a quarterwave monopole antenna cut 712 00:47:07.920 --> 00:47:13.239 for twenty eight point five megaherts. So remember a quarterwave, 713 00:47:13.280 --> 00:47:15.519 you're gonna use two hundred and forty six divided by 714 00:47:15.519 --> 00:47:18.519 the frequency, so two hundred and forty six it's a 715 00:47:18.599 --> 00:47:21.679 quarterwave two forty six divided by twenty eight point five 716 00:47:22.679 --> 00:47:26.760 eight point six feet, So a ten meter UH quarterway 717 00:47:26.880 --> 00:47:29.559 vertical is about eight and a half feet all right, 718 00:47:29.760 --> 00:47:33.840 HF mobile HF and antennas UH they're often some ford 719 00:47:33.880 --> 00:47:36.840 of a ground plane UH. Most popular is the vertically 720 00:47:36.880 --> 00:47:41.320 oriented whip antenna for mobile operation. A full sized quarterway 721 00:47:41.480 --> 00:47:44.039 mobile whip, though, is really not feasible on bands below 722 00:47:44.079 --> 00:47:48.480 twenty eight twenty four megaherts just too long, so you 723 00:47:48.599 --> 00:47:53.519 often you'll see what what what they call loading. There's 724 00:47:53.519 --> 00:47:56.400 some loading techniques that are used to increase the electrical length. 725 00:47:57.360 --> 00:48:00.519 Usually sometimes you'll see loading coils, a coil added to 726 00:48:00.559 --> 00:48:04.480 the base or or somewhere along the length. Sometimes you'll 727 00:48:04.480 --> 00:48:09.000 see what's called capacitive hats their spokes or look like 728 00:48:09.039 --> 00:48:12.039 a wheel shaped structure added near the top of the antenna. 729 00:48:12.719 --> 00:48:15.199 And then there's linear loading whereus part of the antenna 730 00:48:15.280 --> 00:48:18.440 is folded back on itself. So these techniques are all 731 00:48:20.239 --> 00:48:22.480 devised to load the antenna to make it think it's 732 00:48:22.519 --> 00:48:27.639 electrically longer than it really is. Another common feature of 733 00:48:27.639 --> 00:48:30.800 mobile whips is the corona ball at the tip. It 734 00:48:30.840 --> 00:48:33.360 does add a small amount of loading capacitance, but its 735 00:48:33.400 --> 00:48:37.119 main purpose is to eliminate high voltage discharged from the 736 00:48:37.159 --> 00:48:42.000 sharp tip of the antenna while transmitting A loaded antenna 737 00:48:42.639 --> 00:48:45.000 is not as efficient as a full size straight whip, 738 00:48:45.440 --> 00:48:49.320 and we'll have a small operating band without without retuning. 739 00:48:49.960 --> 00:48:54.400 When you add a loading coil to an end to 740 00:48:54.440 --> 00:48:57.880 an antenna puts a real high que in that area 741 00:48:57.880 --> 00:49:00.800 of the band that you're operating in. So if you 742 00:49:00.960 --> 00:49:02.719 if you've got a large band, you may have to 743 00:49:02.760 --> 00:49:05.039 retune it to as you've moved throughout the band because, 744 00:49:05.239 --> 00:49:07.400 like I said, it's it's tuned for a it's got 745 00:49:07.440 --> 00:49:14.039 a very narrow high queue on it. The screwdriver antenna design, 746 00:49:14.639 --> 00:49:17.559 which is a whip with an adjustable coil at the base, 747 00:49:17.880 --> 00:49:22.559 changes the inductance. It has gained popularity for HF mobile operation. 748 00:49:22.800 --> 00:49:26.400 Is a good compromise between performance and convenience. And you 749 00:49:26.440 --> 00:49:27.960 may have seen them. There's a big coil at the 750 00:49:27.960 --> 00:49:31.800 base and as you've moved between the bands, the coil 751 00:49:31.880 --> 00:49:36.000 moves up and down, changing the inductance. Pretty effective antenna. Great, 752 00:49:36.199 --> 00:49:40.440 Like I said, great, great compromise antenna for HF mobile operations. 753 00:49:42.039 --> 00:49:44.400 So what's the effects of ground on these antennas. A 754 00:49:44.440 --> 00:49:48.480 dipoles feed point impedance and radiation pattern are both affected 755 00:49:48.480 --> 00:49:52.519 by its physical height above ground. The feedpoint impedance is 756 00:49:52.559 --> 00:49:56.239 affected because the electrical image is electrically reversed from the 757 00:49:56.320 --> 00:50:00.400 actual dipole. As the image and antenna get closer to together, 758 00:50:00.639 --> 00:50:03.559 the actual antenna begins to be shorted out by the image. 759 00:50:04.280 --> 00:50:07.119 So below a quarter wavelength and height dipoles feed point 760 00:50:07.119 --> 00:50:10.159 and penis steadily decreases until it's close to the ground level. 761 00:50:10.480 --> 00:50:13.880 It's going to be close to zero. So so it's 762 00:50:13.880 --> 00:50:15.760 important to get the ground to get the antenna at 763 00:50:15.840 --> 00:50:20.280 least usually half a wave length up if if, if 764 00:50:20.320 --> 00:50:23.559 you can. Sometimes you can't do that, and I always 765 00:50:23.559 --> 00:50:26.199 say do the best you can. Try to meet the 766 00:50:26.920 --> 00:50:30.480 you know, the guidelines, but get it, get something up, 767 00:50:30.519 --> 00:50:32.840 get on the air. That's the main that's the main thing. 768 00:50:35.159 --> 00:50:37.800 This this chart here shows the feed point penions of 769 00:50:37.840 --> 00:50:42.320 a horzonal dipole over perfect ground and see it varies 770 00:50:42.360 --> 00:50:46.119 dramatically with the height at ground level down here to 771 00:50:46.159 --> 00:50:50.199 the bottom it's shorted out. Basically it's zero and see 772 00:50:50.239 --> 00:50:54.280 antenna moves up gradually it approaches about seventy two oms 773 00:50:54.880 --> 00:51:01.480 about feed point penance in free in free space above 774 00:51:01.519 --> 00:51:05.559 a quarter of the above one quarter wavelength impedance varies 775 00:51:05.599 --> 00:51:08.480 as suggested in this figure over here, eventually reaching a 776 00:51:08.679 --> 00:51:12.840 stable value at a height of several wavelengths. So you know, 777 00:51:12.880 --> 00:51:14.559 so eventually as you get it hired and hire it 778 00:51:14.559 --> 00:51:18.199 finally stabilizes up here. About seventy two oms is the 779 00:51:18.199 --> 00:51:20.039 feed point and penance when you get it real high, 780 00:51:20.079 --> 00:51:24.119 so uh fifty oms. Feed point impedance you can see 781 00:51:24.159 --> 00:51:28.760 here is about point two wavelengths above. So this chart 782 00:51:28.840 --> 00:51:30.800 just shows that that the height above ground is going 783 00:51:30.880 --> 00:51:34.159 to change it then the feed point penance, so you 784 00:51:34.199 --> 00:51:38.719 have to you have to compensate for that. High above 785 00:51:38.719 --> 00:51:41.760 ground also affects the radiation pattern because of reflection of 786 00:51:41.800 --> 00:51:46.039 the antenna's radiated energy by the ground. The direct and 787 00:51:46.199 --> 00:51:50.159 reflected signals take different amounts of time to travel to 788 00:51:50.199 --> 00:51:53.239 the receiving antenna, so they can add together, cancel each other, 789 00:51:53.840 --> 00:51:57.559 or any combination in between. So what happens when a 790 00:51:57.599 --> 00:52:00.400 dipole is raised in steps from a very very low 791 00:52:00.480 --> 00:52:04.280 height to more than one wavelength above ground And this 792 00:52:04.360 --> 00:52:07.800 figure shows some of those. These are four or four 793 00:52:07.840 --> 00:52:11.760 plots at different wavelength heights above ground. As a dipole 794 00:52:12.360 --> 00:52:15.079 starting at at one eighth wavelength above ground is raised, 795 00:52:15.519 --> 00:52:19.079 the effects of its electrical ground image caused the elevat 796 00:52:19.400 --> 00:52:24.679 elevation pattern to flatten out at multiples of the half wavelengths. 797 00:52:24.880 --> 00:52:27.360 The height pattern has a null in the inverted direction 798 00:52:27.480 --> 00:52:31.440 because the direct and reflected signals canceled at heights below 799 00:52:31.639 --> 00:52:35.039 half wavelength. The Dipolese pattern is almost omnidirectional and is 800 00:52:35.159 --> 00:52:39.800 maximum straight up, so the height above ground will change 801 00:52:40.000 --> 00:52:46.440 your radiation pattern of your diet of your dipole. There's 802 00:52:46.480 --> 00:52:49.960 another intendant called end VIZ, which is near vertical incident 803 00:52:50.000 --> 00:52:54.119 skywave propagation. These signals that these are signals that go 804 00:52:54.199 --> 00:52:57.760 straight up. UH signals radiated at high vertical angles on 805 00:52:57.840 --> 00:53:01.079 low frequencies are usually reflected back in the ground over 806 00:53:01.119 --> 00:53:06.440 a wide area, ensuring good communication. Horizontal dipoles from one 807 00:53:06.480 --> 00:53:10.639 tent to quarter wavelength high I produce an omnidirectional high 808 00:53:10.719 --> 00:53:14.599 out angle pattern ideal for envis opper ideal for the 809 00:53:14.679 --> 00:53:17.760 envas used like the previous chart showed, when that antenna 810 00:53:17.800 --> 00:53:20.880 got close to the ground, you saw the radiation pattern 811 00:53:21.119 --> 00:53:23.719 go more up in a round ball up towards the sky. 812 00:53:24.400 --> 00:53:28.679 So by lowering your antenna you can change the effect 813 00:53:29.119 --> 00:53:32.079 of its radiation pattern and use it to bounce off 814 00:53:32.079 --> 00:53:36.360 the sky and talk regionally. It's used by many public 815 00:53:36.400 --> 00:53:42.199 service teams. Polarization also affects the amount of signal that 816 00:53:42.280 --> 00:53:45.559 is lost from the resistance of the ground. Radio waves 817 00:53:46.079 --> 00:53:49.400 reflected from the ground have lower loss when the polarization 818 00:53:49.480 --> 00:53:51.519 of the wave is parallel to the ground that is 819 00:53:51.559 --> 00:53:55.559 horizontally polarized. Because the radiation pattern is made up of 820 00:53:55.599 --> 00:53:59.559 reflected waves, Combining the direct waves that are not reflected 821 00:54:00.239 --> 00:54:07.360 reflection loss results in stronger maximum signal strength. So here's 822 00:54:07.400 --> 00:54:11.519 some antenna terms. Feed point impedance that's the ratio of 823 00:54:11.679 --> 00:54:15.760 RF voltage to current and an antenna speed point resonant. 824 00:54:16.159 --> 00:54:19.079 When an antenna feed point impedance is completely resistant with 825 00:54:19.159 --> 00:54:22.000 no reactants, we talked about that yesterday. A little bit 826 00:54:22.559 --> 00:54:27.280 radiation pattern graph of antennas signal strength in every direction 827 00:54:27.920 --> 00:54:31.000 or at every vertical angle. That's a radiation pattern. The 828 00:54:31.039 --> 00:54:34.760 as myth pattern shows signal strength in the horizontal directions. 829 00:54:35.360 --> 00:54:41.000 Elevation patterns shows signal strength in the vertical direction. Lobes 830 00:54:41.760 --> 00:54:44.480 is a region in the radiation pattern where antenna is 831 00:54:44.559 --> 00:54:48.000 radiating a signal. Okay, that's the lobe, and then the 832 00:54:48.079 --> 00:54:50.079 nulls are the points at which radiation is that it's 833 00:54:50.119 --> 00:54:56.199 a minimum isotropic antenna radiates equally in all possible directions. 834 00:54:57.599 --> 00:55:01.519 Omni directional antenna radiates a signal equally in every horizontal direction. 835 00:55:02.639 --> 00:55:08.440 A directional antenna radiates provincially in one or more directions. 836 00:55:09.280 --> 00:55:13.480 Gain is a concentrated transmitted or received signals in a 837 00:55:13.519 --> 00:55:17.920 specific direction. Front to back ratio is a ratio of 838 00:55:18.159 --> 00:55:21.400 gain in the preferred or forward direction to the opposite direction, 839 00:55:22.400 --> 00:55:24.679 and front the side ratio is the ratio of gain 840 00:55:24.719 --> 00:55:28.159 in the preferred or four direction to directions at right angles. 841 00:55:28.679 --> 00:55:31.840 So those are some antenna terms that that that you 842 00:55:31.840 --> 00:55:34.760 will run into you if you look at an antenna 843 00:55:34.760 --> 00:55:37.039 spect some some of these things are spect out there 844 00:55:37.440 --> 00:55:39.840 and some of these things depending on what you're trying 845 00:55:39.840 --> 00:55:42.360 to do. These are important things that you'll need to 846 00:55:42.360 --> 00:55:45.039 consider choosing and the type of antenna that you want 847 00:55:45.079 --> 00:55:49.639 to use. Okay, what's the purpose of a capacity's hat 848 00:55:49.679 --> 00:55:51.840 on a mobile antenna? Do you remember that's the little 849 00:55:51.840 --> 00:55:54.679 ball that's up at the top of the vertical. Its 850 00:55:54.719 --> 00:56:01.199 primary it's primary thing is to u to increase the 851 00:56:01.239 --> 00:56:03.920 power handling capacity of a whip. Nope, that's not it 852 00:56:04.000 --> 00:56:07.639 reduced raition resistance to electrically LinkedIn. It's physically shorten the 853 00:56:07.719 --> 00:56:10.199 antenna to lower the variation angle have to be c 854 00:56:11.559 --> 00:56:14.760 but its primary purpose remember too, is to static discharge. 855 00:56:15.440 --> 00:56:17.639 What is the purpose of the corona ball. The same 856 00:56:17.679 --> 00:56:21.719 thing on the HF mobile antenna, and that's to reduce 857 00:56:21.840 --> 00:56:24.199 RF voltage discharged from the tip of the antenna while 858 00:56:24.199 --> 00:56:30.000 transmitting D So what is one disadvantage of using a 859 00:56:30.039 --> 00:56:33.079 shortened mobile antenna as opposed to a full sized antenna. 860 00:56:35.280 --> 00:56:40.440 Let's see, that's the operating bandwidth may be very limited, 861 00:56:40.800 --> 00:56:44.639 right because usually you don't have a full size antenna. 862 00:56:44.639 --> 00:56:46.039 You get your gonna going to shorten it. And to 863 00:56:46.039 --> 00:56:47.480 make it too, you used to put a coil in 864 00:56:47.519 --> 00:56:50.599 and that's gonna really affect where you can operate in 865 00:56:50.639 --> 00:56:54.239 that particular band because it's a high Q circuit, which 866 00:56:54.239 --> 00:56:56.159 is the following is a common way to adjust the 867 00:56:56.159 --> 00:57:00.280 feed point impedance of an elevated quarterwave ground plane CLI 868 00:57:00.360 --> 00:57:03.679 intendent to be approximately fifty OS. Remember we talked about there. 869 00:57:03.719 --> 00:57:05.599 This is where you take those ground radios. We've got 870 00:57:05.639 --> 00:57:08.119 a vertical now. And if you bend them, if you 871 00:57:08.199 --> 00:57:10.920 bend them down just a little bit, uh, bend them 872 00:57:11.199 --> 00:57:15.400 slightly downwards, Uh, that will help raise the input, the 873 00:57:15.400 --> 00:57:20.760 the raise the impediance. So it's which is the following 874 00:57:20.760 --> 00:57:24.480 best describes a radiation pattern of a quarterway ground plane 875 00:57:24.559 --> 00:57:29.079 vertical antenna, so about a quarterway round plane, and it 876 00:57:29.159 --> 00:57:34.559 is it's omni directional. What is the radiation pattern of 877 00:57:34.559 --> 00:57:37.480 a dipole antenna and free space and a plane containing 878 00:57:37.599 --> 00:57:42.360 the conductor? Okay, so that would be it's a figure 879 00:57:42.400 --> 00:57:46.800 eight at right angles to the antenna. So you're you 880 00:57:46.840 --> 00:57:50.480 remember it's the radiating is broadside to the antenna up, 881 00:57:50.639 --> 00:57:53.239 not broadside, but forward and back to the anti antennae. 882 00:57:53.280 --> 00:57:58.639 It's antenna itself. How does antenna hype affect the asthmathyl 883 00:57:59.440 --> 00:58:03.760 radiation pattern of a horizontal dipole HF antenna at elevation 884 00:58:03.880 --> 00:58:07.519 angles higher than about forty five degrees? So this is 885 00:58:07.559 --> 00:58:11.280 how does the height affect it? The antenna is less 886 00:58:11.280 --> 00:58:13.480 than a half wave link of that's sort of the 887 00:58:13.559 --> 00:58:16.599 key point. Hi, the asthma pattern is almost omni directional. 888 00:58:16.719 --> 00:58:19.400 You get lower than that, it starts flattening out. So 889 00:58:19.559 --> 00:58:24.199 see is the answer. Where should the radio wires of 890 00:58:24.199 --> 00:58:28.920 a ground mounted vertical antenna system be placed, let's see, 891 00:58:29.159 --> 00:58:32.079 on the surface or buried a few inches below the ground. 892 00:58:32.119 --> 00:58:33.639 So if you do in the parks, not in the air, 893 00:58:34.199 --> 00:58:36.840 lay them on the surface of the ground, that works. That, 894 00:58:37.039 --> 00:58:40.800 That works great. If you've got a permanent inflation at 895 00:58:40.800 --> 00:58:42.320 your house, you may want to bear them a little bit. 896 00:58:42.360 --> 00:58:43.920 You don't run open with the lawn with the lawn more, 897 00:58:45.320 --> 00:58:49.960 but don't bear them, don't bury them too low. How 898 00:58:50.000 --> 00:58:52.239 does the feed point impedant of a horizontal half wave 899 00:58:52.320 --> 00:58:55.079 dipole attended change as the antenna height is reduced to 900 00:58:55.199 --> 00:58:58.679 one tenth of its wavelength above ground? Okay, so if 901 00:58:58.679 --> 00:59:03.719 you as the the feed point is going to change, 902 00:59:04.239 --> 00:59:08.480 it's gonna get it's gonna decrease as you change the height. 903 00:59:08.639 --> 00:59:10.719 When you it it comes closer to the ground, the 904 00:59:11.920 --> 00:59:14.800 few point pens is gonna get. It's gonna get lower. 905 00:59:15.480 --> 00:59:19.480 Eventually get on the ground, it goes to zero. How 906 00:59:19.519 --> 00:59:22.039 does the feed point pence of a halfway dipole change 907 00:59:22.400 --> 00:59:24.639 as the feed point is moved from the center towards 908 00:59:24.719 --> 00:59:27.760 the end. So the feed point penance you remember of 909 00:59:28.199 --> 00:59:32.039 a center fed dipoles around sixty something else, the more 910 00:59:32.119 --> 00:59:34.440 you move it off of the center clos to the edge, 911 00:59:34.559 --> 00:59:40.719 it increases. So the a the impediance of an infed 912 00:59:40.800 --> 00:59:47.159 diepoles about twenty five hundred homes off center fed use 913 00:59:47.239 --> 00:59:52.360 the quarterwave, then it's about two hundred or two. It's 914 00:59:52.360 --> 00:59:55.800 about got about two hundred homes. So as you go 915 00:59:55.880 --> 01:00:00.239 from the center to the end, the few point pace increases. 916 01:00:01.719 --> 01:00:03.840 Which of the thowing is an advantage of a horizontally 917 01:00:03.840 --> 01:00:09.400 polarized as compared to vertically polarized antenna. Lower you have 918 01:00:09.440 --> 01:00:13.760 lower ground losses. What is the approximate length of a 919 01:00:13.760 --> 01:00:16.840 half wave dipole antenna cup? For fourteen point twenty five, 920 01:00:17.719 --> 01:00:21.039 So number's four ninety two divided by fourteen point twenty five, 921 01:00:22.480 --> 01:00:25.760 twenty meters is going to be about thirty three feet. 922 01:00:28.119 --> 01:00:31.239 All right, there's there's the equation four ninety two divide 923 01:00:31.239 --> 01:00:34.840 by fourteen point twenty five, it's thirty four point five, 924 01:00:35.039 --> 01:00:38.559 So thirty four point five in an answer, But you're 925 01:00:38.559 --> 01:00:41.480 gonna you're gonna get the closest one, which is D three. 926 01:00:43.960 --> 01:00:46.840 What is approximate wavelength of a half wave dipole antenna 927 01:00:46.880 --> 01:00:49.880 cup for three point five to five, it's going to 928 01:00:49.960 --> 01:00:55.199 be about one hundred and thirty two feet, all right, 929 01:00:55.239 --> 01:00:58.519 so remember take fortety two divided by the frequency to 930 01:00:58.639 --> 01:01:02.800 the half wave length that's going to be answered. Okay, 931 01:01:03.119 --> 01:01:06.199 how about we got a quarterwave. Now, remember just sitt 932 01:01:06.199 --> 01:01:08.159 in a halfwave, so it's not four ninety two, it's 933 01:01:08.199 --> 01:01:11.440 a quarterwave. So it's going to be two forty six 934 01:01:12.440 --> 01:01:15.599 divided by the frequency. In this case it's about eight feet. 935 01:01:16.000 --> 01:01:18.400 So when they ask these questions, you got to are 936 01:01:18.400 --> 01:01:20.440 they ask them for the halfwave which is four ninety 937 01:01:20.440 --> 01:01:23.320 two or the quarterwave which is half of that two 938 01:01:23.360 --> 01:01:26.559 forty six? So keep that in mind when you see 939 01:01:26.639 --> 01:01:31.599 this question. Are they asking for the halfwave or the Quarterwavey? 940 01:01:31.679 --> 01:01:34.199 How does antenna gains? State it in DBI compared to 941 01:01:34.239 --> 01:01:37.840 the game stated in dB for the same antenna. So 942 01:01:37.960 --> 01:01:40.719 the relationship is two point one five dB. But is 943 01:01:40.760 --> 01:01:43.639 it higher or or or lower? And this in this 944 01:01:43.679 --> 01:01:46.639 case it's actually higher. How does an antenna gain if 945 01:01:46.639 --> 01:01:49.800 you have a DBI antenna compared to a DVD which 946 01:01:50.039 --> 01:01:53.199 is a dB dipole, it's two point one five higher. 947 01:01:55.480 --> 01:01:57.960 Which of the following antenna types will be most effective 948 01:01:58.000 --> 01:02:01.800 as a near vertical incident skywave in is antenna short 949 01:02:01.800 --> 01:02:07.519 skip communications on forty meters during the day. Okay, horizontal 950 01:02:07.519 --> 01:02:10.360 dipole places one hundred and ten to one quarter wavelength 951 01:02:10.400 --> 01:02:14.039 above ground, a quarter to a half half above it's 952 01:02:14.079 --> 01:02:17.800 going to be a horizontal dipole, and it's going to 953 01:02:17.840 --> 01:02:20.920 be Remember, the closer you get to the ground, the 954 01:02:20.920 --> 01:02:24.119 more the radiation patterns is elevated up, so it should 955 01:02:24.159 --> 01:02:28.119 be a here it is, so let's ten a quarter 956 01:02:28.159 --> 01:02:30.840 wave to a tenth. Closer you get to the ground, 957 01:02:30.920 --> 01:02:33.440 the more radiation is going to be reflected up to 958 01:02:33.480 --> 01:02:36.639 the sky. Okay, what is the feed point impedance of 959 01:02:36.679 --> 01:02:41.320 an INFED half wave antenna. Let's see INFED is going 960 01:02:41.400 --> 01:02:43.880 to be two twenty five hundred homes, so we'd say 961 01:02:43.920 --> 01:02:48.559 very high in this case. D How does a screwdriver 962 01:02:48.599 --> 01:02:54.039 mobile antenna adjust its feed point impedance? It varies the 963 01:02:54.079 --> 01:02:57.800 loading with an end with the inducted so you'll see 964 01:02:57.800 --> 01:02:59.559 a coil at the bottom and it moves up and down. 965 01:02:59.599 --> 01:03:02.119 That coil is an is an inductor, so will be 966 01:03:02.239 --> 01:03:05.800 it varies in the inductance B. What is the common 967 01:03:05.880 --> 01:03:10.679 name of a dipole with a single central support. It's 968 01:03:10.679 --> 01:03:17.039 the inverted B configuration. Okay, let's talk about yaggy antennas. 969 01:03:17.599 --> 01:03:20.960 Directional antenna just create gain as well as rejecting interference 970 01:03:21.000 --> 01:03:24.719 and noise from other than the desired direction. By aiming 971 01:03:24.719 --> 01:03:29.199 your antenna in the direction shown in the asmithal projection map, 972 01:03:29.599 --> 01:03:32.079 you'll be beaming your signal directly at the other station. 973 01:03:32.280 --> 01:03:34.760 So as you point your antenna, that's the direct On 974 01:03:34.840 --> 01:03:37.800 a yaggy antenna, the where you point it, that's the 975 01:03:37.840 --> 01:03:41.119 direction your energy is going. Dipole, ground plane and random 976 01:03:41.119 --> 01:03:45.840 wire antennas use a single radiating element, but a dipole 977 01:03:46.039 --> 01:03:48.519 is an arrayed antenna. It uses two or more elements 978 01:03:48.519 --> 01:03:51.760 to create a maximum field strength in a specific direction. 979 01:03:52.639 --> 01:03:56.000 It's called the main lobe or major lobe of the 980 01:03:56.079 --> 01:04:03.000 radiation pattern. Two tie of arrays. There's the driven pair 981 01:04:03.159 --> 01:04:07.000 and parasitic and a driven array. All the antenna elements are 982 01:04:07.000 --> 01:04:10.840 connected to the transmitter and are called driven elements. Parasitic 983 01:04:10.920 --> 01:04:13.840 array one or more of the elements are not connected 984 01:04:13.840 --> 01:04:16.840 to the feed line but influence the antennas patterned by 985 01:04:17.360 --> 01:04:21.559 interacting with the radiated energy from the driven elements. Whether 986 01:04:21.639 --> 01:04:25.199 an array is driven or parasitic, it creation pattern is 987 01:04:25.199 --> 01:04:30.519 determined by the constructionive and destructive interference. If in phase, 988 01:04:30.719 --> 01:04:34.079 they will reinforce each other, out of phase, they will cancel. 989 01:04:36.320 --> 01:04:40.000 Most popular of all direction antennas is the yaggy because 990 01:04:40.039 --> 01:04:43.800 of its simple construction and good performance. Yaggy is a 991 01:04:43.840 --> 01:04:47.199 parasitic array with a single driven element in at least 992 01:04:47.320 --> 01:04:52.920 one parasitic element. The driven element is a resident dipole 993 01:04:53.559 --> 01:04:57.760 approximately halfwave length long. Parasitic elements placed in the direction 994 01:04:57.840 --> 01:05:01.360 of the maximum gain are called directors and the and 995 01:05:01.480 --> 01:05:05.440 are slightly shorter than the driven element. Parasitic elements in 996 01:05:05.480 --> 01:05:09.239 the direction of the minimum gain are called reflectors and 997 01:05:09.280 --> 01:05:12.599 are slightly longer than the driven element. The front to 998 01:05:12.679 --> 01:05:15.119 back ratio is the ratio of signal strength to the 999 01:05:15.159 --> 01:05:18.320 peak of the radiation patterns major lobe and that it 1000 01:05:18.719 --> 01:05:22.159 and that to that and the exactly the opposite direction. 1001 01:05:22.320 --> 01:05:26.159 So the front to back ratio is how much energy 1002 01:05:26.199 --> 01:05:30.360 goes forward versus how much energy goes back. Okay is 1003 01:05:32.800 --> 01:05:36.039 two element yaggy shown in this picture. Here with a 1004 01:05:36.079 --> 01:05:41.199 single parasitic element, you can see we've got a driven 1005 01:05:41.239 --> 01:05:44.360 element here, that's your dipole. You've got a director, this 1006 01:05:44.400 --> 01:05:48.000 is the direction of radiation, and you've got a reflector 1007 01:05:48.119 --> 01:05:54.199 in the back. So this is the way the antennae 1008 01:05:54.199 --> 01:05:59.239 is obstructed, the way that it works. Yaggy design trade offs. 1009 01:06:01.119 --> 01:06:04.239 Primary variables for Yaggy antennas are length and diameter of 1010 01:06:04.239 --> 01:06:07.400 each element and their placement along the boom of the antenna. 1011 01:06:08.679 --> 01:06:12.039 These affect the gain s WR front to back ratio 1012 01:06:12.159 --> 01:06:15.960 in different ways. The more directors you have this increases 1013 01:06:16.000 --> 01:06:19.079 the gain. A longer boom with the fixed number of 1014 01:06:19.119 --> 01:06:22.440 directors increases gain up to the maximum length, beyond which 1015 01:06:22.480 --> 01:06:27.800 gain is reduced. Larger diameter elements reduce SWR variation. With 1016 01:06:27.920 --> 01:06:32.840 frequency placing and tuning of elements effects gain and feed 1017 01:06:32.880 --> 01:06:37.880 point impedance. So all those factors come into play when 1018 01:06:37.880 --> 01:06:40.960 you're trying to design your and your antenna. There are 1019 01:06:40.960 --> 01:06:42.960 other general rules of cause and effects, but these are 1020 01:06:43.000 --> 01:06:47.880 typically on decision of the antenna designer yourself. But when 1021 01:06:47.920 --> 01:06:52.079 you go purchase Yaggy and Yaggy antenna, someone has already 1022 01:06:52.079 --> 01:06:55.079 figured out the size of the beam and the size 1023 01:06:55.119 --> 01:06:59.239 of the directors, and the parasitic elements, and you'll buy 1024 01:06:59.239 --> 01:07:01.679 it based on front back ratio in the game that 1025 01:07:01.719 --> 01:07:05.400 you need, going in the game that you are desired. 1026 01:07:09.519 --> 01:07:14.159 Most shaggy designs have desirable radiation patterns also have a 1027 01:07:14.199 --> 01:07:18.159 feed point impedance somewhere below fifty oms. With regular coacts 1028 01:07:18.840 --> 01:07:22.000 with the feedpoint impedance from twenty to twenty five oms, 1029 01:07:22.440 --> 01:07:27.039 this results in an undesirable SWR two to one. So 1030 01:07:27.079 --> 01:07:29.800 the most common technique for matching the impedance is a 1031 01:07:29.840 --> 01:07:34.119 gamma match. A gamma match is a shortened section of 1032 01:07:34.159 --> 01:07:38.519 parallel conductor transmission line that uses the driven element as 1033 01:07:38.559 --> 01:07:43.480 one of its conductors. Transmission line transforms the low impedance 1034 01:07:44.000 --> 01:07:47.440 of the feed point to a higher value. An adjustable capacitor, 1035 01:07:47.480 --> 01:07:51.119 either an actual variable capacitor or a shorter piece of 1036 01:07:51.159 --> 01:07:54.840 insulated wire inside a hollow gamma rod is used to 1037 01:07:54.840 --> 01:07:57.199 adjust the gamma match for s WR one to one. 1038 01:07:58.519 --> 01:08:01.000 A mechanical advantage of the game a match over other 1039 01:08:01.039 --> 01:08:04.199 techniques is that the driven element needed needs not to 1040 01:08:04.239 --> 01:08:10.440 be insulated from the boom, which simplifies the construction. UH 1041 01:08:10.599 --> 01:08:14.400 there's a beta match, which or sometimes reference as a hairpin, 1042 01:08:15.519 --> 01:08:19.000 is a short length or stub a parallel conductor transmission 1043 01:08:19.079 --> 01:08:23.600 line connected directly across the driven element feedpoint. The stub 1044 01:08:23.680 --> 01:08:27.479 acts as an inductive reactants that can compensate for any 1045 01:08:27.479 --> 01:08:31.399 capacity of reactants at the feedpoint. The balance is used 1046 01:08:31.439 --> 01:08:34.079 to maintain the electrical balance between both halves of the 1047 01:08:34.159 --> 01:08:37.880 driven element. Other techniques such as the Omega match and 1048 01:08:37.960 --> 01:08:42.000 penis transformers and transmission line subs are also described, and 1049 01:08:42.119 --> 01:08:47.640 you can read those in the ABRL handbook. Here's some 1050 01:08:47.720 --> 01:08:51.600 practice questions. Which of the following describes an as methyl 1051 01:08:52.000 --> 01:08:56.680 projection map? Okay, the map that shows the actual land 1052 01:08:56.720 --> 01:08:59.359 mask says, wouldn't be that. It's going to be a 1053 01:08:59.399 --> 01:09:02.720 map that shows the bearing distance for specific location. Okay, 1054 01:09:02.760 --> 01:09:04.880 So that when you bind a yaggy antenna member, it's 1055 01:09:04.880 --> 01:09:08.079 gonna it's gonna project and as anthyl projection in the 1056 01:09:08.159 --> 01:09:11.800 in the four direction. Uh. Which of the following would 1057 01:09:11.800 --> 01:09:18.800 increase the bandwidth of a yaggy and antenna larger diameter elements? Uh? 1058 01:09:19.159 --> 01:09:24.239 The spacing is is uh is has will affect the 1059 01:09:24.279 --> 01:09:26.159 gain and the impediance, but the lord of the element 1060 01:09:26.279 --> 01:09:28.479 size actually helps with the band with the with with 1061 01:09:28.520 --> 01:09:32.279 the bandwidth which is approximate link of the driven element 1062 01:09:32.399 --> 01:09:36.399 of a yaggy antenna, that'd be a halfwave link. Remember 1063 01:09:36.439 --> 01:09:40.000 it's a The driven element is a dipole, so it's 1064 01:09:40.000 --> 01:09:43.279 half wave length. Uh. How do the lengths of the 1065 01:09:43.319 --> 01:09:46.079 three element yaggy, reflector and director compared to that of 1066 01:09:46.119 --> 01:09:50.760 the driven element? Uh, the reflector, let's see, the reflector 1067 01:09:50.840 --> 01:09:53.800 is going to be longer. Director's gonna be short. Its 1068 01:09:53.840 --> 01:09:57.439 like it's gonna be a here. Yeah, he's the answer. 1069 01:09:57.560 --> 01:10:02.199 So the usually the so so the director's right behind 1070 01:10:02.239 --> 01:10:07.880 the driven element, towards the back of the antenna, it's 1071 01:10:07.920 --> 01:10:10.800 a little bit longer. And then in front of the 1072 01:10:10.880 --> 01:10:16.399 driven element. What's the primary effect of increasing bloom lengths 1073 01:10:16.399 --> 01:10:18.960 and adding directors to the and to the yaggy antenna? 1074 01:10:19.600 --> 01:10:24.600 You're going to increase the game. Kay. What does front 1075 01:10:24.640 --> 01:10:27.560 to back ratio mean in reference to a yaggy and 1076 01:10:30.600 --> 01:10:35.159 it would be the uh power radiated in the major 1077 01:10:35.279 --> 01:10:38.479 lobe compared to the opposite direction. Okay, So it's the 1078 01:10:38.600 --> 01:10:42.800 ratio of how much power goes forward to that to 1079 01:10:42.880 --> 01:10:45.199 the radio power forward versus the radio power in the back. 1080 01:10:46.720 --> 01:10:49.119 What is meant by the main lobe of a director 1081 01:10:49.319 --> 01:10:55.279 of a direct directive directional antenna? It's the direction of 1082 01:10:55.319 --> 01:10:59.279 which the maximum field strength from the antenna is radiated. 1083 01:10:59.479 --> 01:11:01.840 It's it's that is that direction. So the main lobe 1084 01:11:01.920 --> 01:11:05.399 on a yaggy is usually on a yaggy is where 1085 01:11:05.680 --> 01:11:08.000 is where the elements where the the antenna is pointing 1086 01:11:08.039 --> 01:11:12.439 out to the front of the antenna. Which of the 1087 01:11:12.479 --> 01:11:15.239 falling can be adjusted to optimize forward gain, front to 1088 01:11:15.319 --> 01:11:20.039 back ratio or SWR bandwidth of a yaggy antenna, length 1089 01:11:20.119 --> 01:11:24.079 of the boom, number of elements spacing all those things deep. 1090 01:11:26.520 --> 01:11:29.359 What is a beta or hair painting or or hair 1091 01:11:29.439 --> 01:11:36.319 pin match. It's a shorted transmission line stub place at 1092 01:11:36.319 --> 01:11:39.960 the feet point of a yaggy antenna to provide impedance matching. 1093 01:11:40.159 --> 01:11:42.960 So it's it's a way to remember the the yagy 1094 01:11:42.960 --> 01:11:45.560 itself is about twenty five homes. He needs something to 1095 01:11:45.840 --> 01:11:47.800 raise the impedance up. Its about fifty oms of your 1096 01:11:48.079 --> 01:11:52.880 to to your system. And the beta or hair pin 1097 01:11:52.960 --> 01:11:55.760 match is a transmission line stub that that that that 1098 01:11:55.800 --> 01:12:00.159 does that transformation for you. Whatis is the fallowing is 1099 01:12:00.159 --> 01:12:03.800 a characteristic of using a gamma match with a yaggy antenna. 1100 01:12:07.039 --> 01:12:10.720 A Let's see, it does not require that the driven 1101 01:12:10.800 --> 01:12:14.479 element be insulated from the boom. Our next section, we're 1102 01:12:14.479 --> 01:12:17.720 going to talk about loop antennas, specialized antennas, and feed lines. 1103 01:12:19.600 --> 01:12:23.520 So what's a loop antenna. It can be a circular, square, triangular, 1104 01:12:23.640 --> 01:12:26.960 or any simple open shape that is not too narrow. 1105 01:12:28.760 --> 01:12:31.319 Feed line can be attached at a break in the loop, 1106 01:12:31.399 --> 01:12:33.079 or a small loop can be used to a couple 1107 01:12:33.239 --> 01:12:36.399 RF energy to the main loop. Square loop with each 1108 01:12:36.520 --> 01:12:38.880 leg a quarter of a wavelength long is called a 1109 01:12:38.960 --> 01:12:44.319 quad loop. A triangle or delta loops are usually symmetrical, 1110 01:12:44.960 --> 01:12:48.119 each leg a third of a wavelength long. A one 1111 01:12:48.159 --> 01:12:52.319 wavelength loop acts electrically like two dipoles connected in the end, 1112 01:12:52.359 --> 01:12:57.079 with the open ends brought together circumforts much larger than 1113 01:12:57.199 --> 01:13:02.000 one wavelength. Typically a current patterns around loop have more 1114 01:13:02.039 --> 01:13:05.600 than two peaks and knowles. This results in an essentially 1115 01:13:05.640 --> 01:13:09.039 omni directional pattern, with the peak angle radiation somewhat lower 1116 01:13:09.119 --> 01:13:15.119 than a dipole at the same height. There's quad and 1117 01:13:15.159 --> 01:13:20.279 delta loop beams. Popular variation of the yaggy antenna uses 1118 01:13:20.279 --> 01:13:23.960 what's called quad loops for elements. It's called a quad 1119 01:13:24.680 --> 01:13:26.920 It has two or more full sized loops mounted on 1120 01:13:26.960 --> 01:13:31.039 a boom. Quad or delta loop. Beam driven elements are 1121 01:13:31.039 --> 01:13:35.039 approximately one wavelength in circumference and operate on the same 1122 01:13:35.079 --> 01:13:39.479 principle of re radiation and face shift as does the yaggy. 1123 01:13:40.319 --> 01:13:43.279 The driven element of a quad is about a quarter 1124 01:13:43.399 --> 01:13:47.840 wavelength per side, and of a symmetrical delta loop about 1125 01:13:47.920 --> 01:13:51.760 a third of a wavelength per side. Quad and delta 1126 01:13:51.760 --> 01:13:54.840 loops reflectors are about five percent longer in circumference than 1127 01:13:54.880 --> 01:13:57.720 the driven element, and the directors about five percent shorter. 1128 01:13:58.600 --> 01:14:01.279 Front to back ratio is generally better for the yaggy. 1129 01:14:01.680 --> 01:14:07.319 It's usually better for the yaggy. Right. Here's the figure. 1130 01:14:07.319 --> 01:14:11.000 Here is showing a wavelength of the loop antennas. So 1131 01:14:11.079 --> 01:14:15.560 this is your antennas. Here the square, and this is 1132 01:14:15.560 --> 01:14:18.760 what the pattern looks like. The direction of maximum signal 1133 01:14:18.800 --> 01:14:22.359 is broadside to the plane of the loop, whether round, 1134 01:14:22.439 --> 01:14:27.079 quad or delta or orienting the loop vertically aims and 1135 01:14:27.159 --> 01:14:30.199 maximum signal towards the horizon, which is good for deep 1136 01:14:30.239 --> 01:14:36.640 which is good for DX. So full way of blue antenna. 1137 01:14:36.640 --> 01:14:39.079 I've got a full wave blue antenna that I use 1138 01:14:39.159 --> 01:14:43.039 one hundred and sixty meters. It's not up very high, 1139 01:14:43.159 --> 01:14:48.159 so uh, but that's the high side that I could 1140 01:14:48.159 --> 01:14:50.960 get it, but you know, one hundred and sixty countries later, 1141 01:14:51.079 --> 01:14:52.920 I think I'm pretty happy with it right now. So 1142 01:14:53.560 --> 01:14:55.840 talk about small loops. When the circumference of the loop 1143 01:14:55.880 --> 01:14:58.560 becomes less than a third of a wavelength, the current 1144 01:14:58.600 --> 01:15:01.319 in the loop becomes relatively uniform all the way around 1145 01:15:01.359 --> 01:15:05.720 the top, which causes so small loops cause radiation patterns 1146 01:15:05.720 --> 01:15:07.960 to develop sharpnols the broad side to the plane of 1147 01:15:07.960 --> 01:15:12.880 the loop. Small loops in wide use. They're in wide 1148 01:15:12.960 --> 01:15:17.479 use as receiving antennas and portable or low profile transmitting antennas. 1149 01:15:17.880 --> 01:15:20.640 The sharpnel broad side to the loop makes them effective 1150 01:15:20.680 --> 01:15:24.520 for direction finding. This is typically small loop. Now they 1151 01:15:24.560 --> 01:15:28.560 have a very high Q. Sometimes they're difficult to tune. 1152 01:15:28.600 --> 01:15:30.800 Some have an automatic tuner that comes with them, which 1153 01:15:30.840 --> 01:15:35.000 is great, but they're very high Q. They're very high 1154 01:15:35.039 --> 01:15:39.439 Q antennas halo antenna which is double bent into a 1155 01:15:39.479 --> 01:15:43.520 circle or square called the squalow with the ends separated 1156 01:15:43.520 --> 01:15:48.000 by a small gap. Not a continuous loop, but otherwise 1157 01:15:48.119 --> 01:15:52.760 viewed as a half wave loop. Usually they're horizontally mounted 1158 01:15:52.800 --> 01:15:57.560 horizontally so they produce an omnidirectional pattern, with the horizontal 1159 01:15:57.560 --> 01:16:01.960 pattern preferred for VHF week signal operating halos for six 1160 01:16:02.000 --> 01:16:03.800 and two meters can be mounted on a vehicle for 1161 01:16:03.840 --> 01:16:09.239 mobile operations. Well, which direction is the maximum radiation from 1162 01:16:09.239 --> 01:16:14.520 a VHF UHF halo antenna. That would be omnidirection in 1163 01:16:14.560 --> 01:16:19.319 the plane of the of the halo. In which direction 1164 01:16:19.560 --> 01:16:22.640 or or direction does in an electrically small loop less 1165 01:16:22.640 --> 01:16:26.079 than one tenth of a wavelength. That's circumference. Have nols 1166 01:16:26.079 --> 01:16:29.640 and his radiation patterns, and that's broadside to the loop. 1167 01:16:30.239 --> 01:16:34.680 Talk about some random wire antennas. It's not practically always 1168 01:16:34.720 --> 01:16:37.479 to have a half wave or a quarterwave long resident antenna. 1169 01:16:38.239 --> 01:16:42.119 A random wire can be used instead, connected directly to 1170 01:16:42.159 --> 01:16:45.319 the output of the transmitter or tuner without a feed line. 1171 01:16:45.600 --> 01:16:48.840 This may result, however, you gotta be careful. Ray eight 1172 01:16:49.079 --> 01:16:52.760 RADI eight random wire antennas may result in significant RF 1173 01:16:52.840 --> 01:16:56.720 currents and vultures at the station equipment r F burns. 1174 01:16:57.319 --> 01:16:59.560 They can give excellent results on any band for which 1175 01:16:59.560 --> 01:17:02.239 the transmit or tuner can accept the feed point impedance. 1176 01:17:03.159 --> 01:17:06.680 Typically got to have a tuner with these because they're 1177 01:17:06.680 --> 01:17:13.159 not because they're not resonant. You can stack antennas stacking 1178 01:17:13.199 --> 01:17:17.359 antennas vertically or horizontally results in more gain and more 1179 01:17:17.399 --> 01:17:20.119 and as more and more directors are added, the beamwidth 1180 01:17:20.119 --> 01:17:23.279 of the main lobe angle between points on the main lobe, 1181 01:17:24.359 --> 01:17:27.920 which gain is three dB or less than maximum narrows. 1182 01:17:28.359 --> 01:17:32.399 Vertically stacking antennas increases gain and narrows the elevation bandwidth. 1183 01:17:33.960 --> 01:17:37.039 Both vertical stacks with the antenna directly above each other 1184 01:17:37.520 --> 01:17:42.800 are spaced about half of a wavelength apart space half wavelength. 1185 01:17:42.840 --> 01:17:46.560 Additional gain for vertical stack of two horizontally polarized beams 1186 01:17:46.640 --> 01:17:50.079 is about three dB. You can double your power by 1187 01:17:50.079 --> 01:17:56.600 adding another antenna on top. There's an example of of 1188 01:17:56.760 --> 01:18:02.359 a horror of horizontally stacked and vert stacked. So stacked 1189 01:18:02.399 --> 01:18:05.600 the antennas produces more gain in the main lobe, and 1190 01:18:06.880 --> 01:18:09.159 two yaggis are stacked vertically at the same mass. So 1191 01:18:09.199 --> 01:18:17.319 here's an example vertical stack horizontally stack. Another antenna called 1192 01:18:17.319 --> 01:18:21.479 the log periodic antenna. TV antennas are often log periodics. 1193 01:18:21.960 --> 01:18:25.520 Log refers to logarithmic and periodic means the spacing of 1194 01:18:25.520 --> 01:18:28.199 the elements, which is referring to the spacing of the 1195 01:18:28.239 --> 01:18:31.880 elements along the boom, the link and spacing of the 1196 01:18:31.880 --> 01:18:36.159 elements increases. Logarithmic logged rhythmically from one end to the 1197 01:18:36.199 --> 01:18:40.279 other's designed to have a constant radiation pattern in low 1198 01:18:40.399 --> 01:18:43.279 s of R over a wide frequency bandwidth as much 1199 01:18:43.279 --> 01:18:46.159 as ten to one, meaning the log periodic can be 1200 01:18:46.279 --> 01:18:50.840 used over several bands. Not as much gain or front 1201 01:18:50.840 --> 01:18:55.199 to back ratio as a yaggy antenna, but wide band 1202 01:18:56.760 --> 01:19:00.399 multi band okay, and a log periodic antenna looks like this. 1203 01:19:02.479 --> 01:19:07.159 It's the log pre dipole array consists of dipoles fed 1204 01:19:07.199 --> 01:19:11.319 by common feed line that alternates polarity between elements. Traditional 1205 01:19:11.319 --> 01:19:20.079 TV antennas sweep the elements slightly forward. Beverage antennas was 1206 01:19:20.119 --> 01:19:24.119 invented by Harold Beverage. They're designed not to have high gain, 1207 01:19:24.199 --> 01:19:27.479 but to reject noise and interfering signals that are not 1208 01:19:27.560 --> 01:19:31.760 from the desired direction. Results in lower signal strength but 1209 01:19:31.800 --> 01:19:34.880 a better signal to noise ratio to referred to as 1210 01:19:34.960 --> 01:19:40.239 a traveling wave antenna, it consists of a long, low wire, 1211 01:19:40.359 --> 01:19:43.079 usually less than twenty feet high, aligned with the preferred 1212 01:19:43.119 --> 01:19:48.760 signal direction. They're used exclusively for direction receiving on MF 1213 01:19:48.800 --> 01:19:52.439 and lower HF bands. Forty meters and longer wavelengths. It's 1214 01:19:52.479 --> 01:19:57.279 high ground losses, and it has high ground losses and 1215 01:19:57.399 --> 01:20:00.279 is too inefficient for use as a transmitting antenna. It's 1216 01:20:00.279 --> 01:20:02.640 a great receive antenna, like I said, and it can 1217 01:20:05.199 --> 01:20:08.600 it can improve your signal to noise radio ratio by 1218 01:20:08.640 --> 01:20:14.680 rejecting some of the noise. Here's an example of the 1219 01:20:14.720 --> 01:20:21.560 beverage antenna, usually one to quarter one to four times 1220 01:20:21.560 --> 01:20:24.600 wavelengths easily kind of close to the ground. It has 1221 01:20:24.640 --> 01:20:28.960 a terminating resistor. That's why it's not great for transmitting, 1222 01:20:29.000 --> 01:20:33.359 because it's gonna absorb all your energy. But it's a 1223 01:20:33.359 --> 01:20:37.159 great receipt antenna. And you can see by the pattern 1224 01:20:37.199 --> 01:20:42.359 there it's it's got great rejection to the back. Okay, 1225 01:20:42.600 --> 01:20:45.199 So signals arriving from the direction of the terminating resistor 1226 01:20:45.199 --> 01:20:48.880 which is pointing towards the back and douce a traveling 1227 01:20:48.960 --> 01:20:52.600 voltage wave along the wire. It gets transferred to the 1228 01:20:52.640 --> 01:20:54.760 feed line and the feed points signals arriving from other 1229 01:20:54.800 --> 01:20:58.439 directions or either broad side of the terminating resistor or 1230 01:20:58.560 --> 01:21:00.800 do not induce voltage waves on the end on the 1231 01:21:00.880 --> 01:21:05.359 and the antenna. So a lot of people use these 1232 01:21:05.439 --> 01:21:07.479 for you know, a lot of your radios have a 1233 01:21:07.560 --> 01:21:10.520 received antenna, and this is one. This is an example 1234 01:21:10.560 --> 01:21:12.680 where where you want to hook that kind of of 1235 01:21:12.680 --> 01:21:17.600 of of of antenna in. Okay talk about multi band antennas, 1236 01:21:19.159 --> 01:21:21.640 but Hams generally mean by multi banded antenna is the 1237 01:21:21.640 --> 01:21:25.119 design that reconfigures itself electrically for each band of operation. 1238 01:21:26.840 --> 01:21:32.000 Those basic multi band antenna is a trapped dipole. Each 1239 01:21:32.079 --> 01:21:37.239 trap is a parallel l C circuit. Resonance acts like 1240 01:21:37.279 --> 01:21:41.560 an open circuit below residence like an adductor, and above 1241 01:21:41.760 --> 01:21:44.039 like a capacity. And we we went through that and 1242 01:21:44.079 --> 01:21:47.960 we talked about ls and sea circuits, tank circuits. At 1243 01:21:47.960 --> 01:21:50.560 lower frequencies, the traps and inductance to the antenna make 1244 01:21:50.600 --> 01:21:55.079 the antenna look electrically longer, and at higher frequency, the 1245 01:21:55.079 --> 01:21:58.760 capacity of electrically shortens the end the the the antenna. 1246 01:22:00.039 --> 01:22:06.239 Usually you'll see these on a bean antenna. It's got 1247 01:22:06.720 --> 01:22:10.520 several traps, and these traps again make this the antenna 1248 01:22:10.600 --> 01:22:14.239 think it's you know, sixty something feet long and it's 1249 01:22:14.319 --> 01:22:16.840 really only twenty five feet long or something like that. 1250 01:22:16.920 --> 01:22:22.079 So they're used quite a bit for bean antennas for 1251 01:22:22.399 --> 01:22:26.199 H for H for HF because you practically couldn't put 1252 01:22:26.199 --> 01:22:29.359 a big yaggy up at forty meters it'd be super long, 1253 01:22:29.560 --> 01:22:36.840 heavy high. So these antennas work pretty good, pretty popular 1254 01:22:37.000 --> 01:22:41.720 for the HF bands, and they worked very They worked 1255 01:22:42.199 --> 01:22:45.960 very very well. Again, you got one antenna that operates 1256 01:22:45.960 --> 01:22:49.439 over multi bands. Trapped diepoles is another one. The lowest 1257 01:22:49.479 --> 01:22:53.239 frequency of operation of an antenna acts like a regular diepole. 1258 01:22:55.039 --> 01:22:57.880 It can be shortened by the inductance of the trap. 1259 01:22:58.319 --> 01:23:02.720 Yaggys can also use traps to work on several bands. 1260 01:23:03.720 --> 01:23:06.319 Three element tri band yaggy with traps and the elements 1261 01:23:06.319 --> 01:23:08.880 works well twenty fifteen and ten. So sort of like 1262 01:23:08.880 --> 01:23:10.840 what we just looked on the previous chart that was 1263 01:23:10.880 --> 01:23:14.800 a a yaggy with traps in it. Some drawbacks with 1264 01:23:14.880 --> 01:23:17.960 traps because it works on multiple bands. It radiates harmonics 1265 01:23:17.960 --> 01:23:22.119 and spurious signals also, and uh so you've got to 1266 01:23:22.159 --> 01:23:25.359 make sure that you've uh that that you get that 1267 01:23:25.479 --> 01:23:29.199 you've got your transmitter tune right and uh to watch 1268 01:23:29.199 --> 01:23:33.560 your spur you signals. Traps lose losses reduced the efficiency 1269 01:23:33.560 --> 01:23:36.760 of the of the of the antenna. They are coil 1270 01:23:37.399 --> 01:23:39.520 and they will absorb some of your and your your 1271 01:23:39.720 --> 01:23:43.720 your energy and they don't radio as well as a 1272 01:23:43.720 --> 01:23:48.960 full sized antenna. But it's a it's a great compromise. Hey, 1273 01:23:49.119 --> 01:23:53.399 what is the characteristics of a random wire HF antenna 1274 01:23:54.039 --> 01:23:59.920 connected directly to the transmitter. Let's see it make cares 1275 01:24:00.000 --> 01:24:04.079 magnificant RF current. That's a that's what you gotta be 1276 01:24:04.119 --> 01:24:07.520 careful for. You gotta look out for because you're you 1277 01:24:07.520 --> 01:24:10.279 can have highest of br on the thing and gotta 1278 01:24:10.319 --> 01:24:13.640 be careful in free space? How does the gain of 1279 01:24:13.720 --> 01:24:18.880 three element UH horizontally polarized jaggy antennas vertically space a 1280 01:24:18.920 --> 01:24:21.319 half wave length apart typically compared to the gain of 1281 01:24:21.359 --> 01:24:23.680 a single element. So, as we talked about, if you 1282 01:24:23.720 --> 01:24:26.359 can stack two of them vertically, you get about a 1283 01:24:26.399 --> 01:24:31.720 three d B gain should be b yep. What's the 1284 01:24:31.720 --> 01:24:40.800 primary function of antenna traps and it's two to enable 1285 01:24:40.880 --> 01:24:46.239 multiban operation. What is an advantage of vertical stacking of 1286 01:24:46.279 --> 01:24:54.439 horizontal polarized yaggy antennas spig selection simultaneous? It narrows the 1287 01:24:54.479 --> 01:24:59.840 main lobe in elevation, that's correct. Which of the following 1288 01:24:59.920 --> 01:25:04.199 is an advantage of a log periodic and antenna h 1289 01:25:04.319 --> 01:25:09.000 H it has wide band will bands? Okay, which of 1290 01:25:09.000 --> 01:25:14.239 the following describes a log periodic antenna. Let's see element 1291 01:25:14.279 --> 01:25:21.920 spacing very logged medically along the boom. That's correct. Game varies, sorry, 1292 01:25:21.920 --> 01:25:25.880 so it had to be eight. Okay, the element spacing 1293 01:25:26.079 --> 01:25:30.560 is logarithmically related. What is the primary use of a 1294 01:25:30.600 --> 01:25:39.039 beverage antenna directional receiving antenna for a for HF bands. 1295 01:25:39.560 --> 01:25:42.199 I think that's the right answer. Remember that's the one 1296 01:25:42.199 --> 01:25:44.479 that's got to resist her in it, and it's not 1297 01:25:44.560 --> 01:25:47.079 good for transmitting, but it's great for receiving, and it 1298 01:25:47.159 --> 01:25:51.600 has uh some directional to it, which is the following 1299 01:25:51.640 --> 01:25:56.359 is a disadvantage of multi band antennas must be used. 1300 01:25:56.399 --> 01:26:02.640 It must be fed ah uh poor harmonic rejection because 1301 01:26:02.720 --> 01:26:07.359 the resonant. So if I've got a twenty forty multi 1302 01:26:07.439 --> 01:26:12.479 dipole and I'm on twenty meters, will I'm also generating 1303 01:26:12.479 --> 01:26:14.359 a forty meter harmonic too, So you got to be 1304 01:26:14.399 --> 01:26:17.520 character and him because that harmonic will be resident on 1305 01:26:17.520 --> 01:26:21.840 one of your of your antennas. Okay, let's talk about 1306 01:26:21.840 --> 01:26:27.079 feed lines and characteristic compedants. Bounce feed lines the system 1307 01:26:27.119 --> 01:26:30.319 two parallel conductors separated by instantly material in the form 1308 01:26:30.600 --> 01:26:36.479 of strips or spacers. They have different characteristic impedances that 1309 01:26:36.680 --> 01:26:40.079 characterize how electromagnetic energy is carried by the feed line. 1310 01:26:41.520 --> 01:26:44.279 For parallel conductor feed lines of radius of conductors and 1311 01:26:44.319 --> 01:26:48.560 the distance between them is determined by the Z which 1312 01:26:48.600 --> 01:26:54.359 is the impediance. Most common type is window line. Typical 1313 01:26:54.560 --> 01:26:57.359 impedance for a window lines about four hundred and fifty ohms, 1314 01:26:57.439 --> 01:27:00.279 some as low as four hundred most common character verst 1315 01:27:00.439 --> 01:27:05.560 of coaxial feed lines UH fifty homes and seventy five homes. 1316 01:27:07.640 --> 01:27:10.800 Here's an example of some of the different types of 1317 01:27:11.359 --> 01:27:15.760 feed lines. This is UH. Yes. See here's a seventy 1318 01:27:15.800 --> 01:27:20.199 five O twin lead four and fifty on window line. 1319 01:27:22.920 --> 01:27:27.319 Coacts with different kinds of dielectric materials, different kinds of shielding. 1320 01:27:29.000 --> 01:27:32.520 A lot of different UH types of coax shielding is 1321 01:27:32.560 --> 01:27:38.000 available and insulting materials, and so you have to you 1322 01:27:38.079 --> 01:27:41.880 have to UH pick the UH coax UH. If you're 1323 01:27:41.960 --> 01:27:44.960 using coacts, you want to pick the get the impedance 1324 01:27:45.000 --> 01:27:48.239 that you want, get the jacketing, get the shielding that 1325 01:27:48.319 --> 01:27:51.560 you want, get the UH jacketing material that you need. 1326 01:27:51.560 --> 01:27:53.840 If you're variant outside, it's going to be in sunlight. 1327 01:27:54.479 --> 01:27:56.439 A lot of factors to consider. Themen picking at your 1328 01:27:56.479 --> 01:27:59.920 coax and your and your feet in your feed lines. 1329 01:28:00.079 --> 01:28:06.079 So right, so's talk about fording reflected power and SWR. 1330 01:28:06.439 --> 01:28:09.279 Feed line transfers all of its power to the antenna 1331 01:28:09.319 --> 01:28:13.319 when the antenna feed line are matched. If the impedances 1332 01:28:13.319 --> 01:28:16.159 don't match, some of that power is reflected back and 1333 01:28:16.199 --> 01:28:19.840 reflected by the antenna back towards the transmitter. So we 1334 01:28:19.920 --> 01:28:23.600 have forward power, it's power traveling down towards the antenna 1335 01:28:23.680 --> 01:28:27.560 and reflected power power that's reflected back. Power in a 1336 01:28:27.600 --> 01:28:30.119 feed line is reflected at any point at which the 1337 01:28:30.159 --> 01:28:33.159 impedance of the feed line changes, so that cannot necessarily 1338 01:28:33.159 --> 01:28:35.119 be at the antenna, but could be at the connector. 1339 01:28:35.319 --> 01:28:38.239 Or you've got an interface coming out of your shack 1340 01:28:38.359 --> 01:28:42.000 to the out to the outside a patch panel. Whenever 1341 01:28:42.159 --> 01:28:45.920 that feed line is interrupted or changes, the impedance can 1342 01:28:46.000 --> 01:28:48.800 change through that and you can get a reflection there. 1343 01:28:51.319 --> 01:28:55.560 SWR the waves carrying forward power and reflected power from 1344 01:28:55.640 --> 01:28:58.920 stationary patterns inside the feed line. It's called SWR. It's 1345 01:28:59.000 --> 01:29:02.279 is called standing waves. The ratio of the peak voltage 1346 01:29:02.399 --> 01:29:04.800 in the standing wave to the minimum voltage is called 1347 01:29:04.800 --> 01:29:10.079 the standing wave ratio. Standingwave ratio measures how well the 1348 01:29:10.119 --> 01:29:14.359 antenna feed line and impedances are matched. One to one 1349 01:29:14.479 --> 01:29:17.880 is a perfect match, none of the power is reflected. 1350 01:29:19.159 --> 01:29:21.880 SWR of infinity in the case that all the power 1351 01:29:22.039 --> 01:29:26.760 was reflected, and SWR is always greater than one to one. 1352 01:29:27.239 --> 01:29:30.359 For example, you always say three to one, you won't 1353 01:29:30.359 --> 01:29:35.680 say one to three. One to one's perfect, So there's 1354 01:29:35.760 --> 01:29:38.840 never a perfect system, so always gonna be a little 1355 01:29:38.840 --> 01:29:43.119 greater than one to one. So how do you calculate SWR? 1356 01:29:43.880 --> 01:29:47.079 SBR is equal to the ratio of the high of 1357 01:29:47.119 --> 01:29:50.279 the higher of antenna feed point impedance or feed line 1358 01:29:50.359 --> 01:29:54.560 character's competence to the lower. So example, what is SWR 1359 01:29:54.600 --> 01:29:58.399 in a fifty feed line connected to a two hundred load, Well, 1360 01:29:58.439 --> 01:30:01.920 that would be two hundred divided box four, so i'd 1361 01:30:01.920 --> 01:30:05.239 be four to one. What's the SWR and a fifty 1362 01:30:05.239 --> 01:30:09.359 on feed line connected to a ten o load fifty 1363 01:30:09.399 --> 01:30:14.600 divided by ten five to one? So remember you're always 1364 01:30:14.600 --> 01:30:17.039 it's gonna be the ratio of the higher one to 1365 01:30:17.119 --> 01:30:18.960 the lower one, right, So you're not going to get 1366 01:30:19.000 --> 01:30:25.760 a number less than one. Okay. SWR can be measured 1367 01:30:25.800 --> 01:30:29.520 anywhere along the feed line. However, However, it's most most 1368 01:30:29.520 --> 01:30:33.119 commonly measured UH at the connector at the connection to 1369 01:30:33.199 --> 01:30:37.359 the trend to the transmitter UH SWR measured by an 1370 01:30:37.439 --> 01:30:42.840 SWR meter, also called the bridge. Transmitting equipment is designed 1371 01:30:42.840 --> 01:30:45.439 to work at full power with an SBR at the 1372 01:30:45.439 --> 01:30:50.600 input impedance feed line of about two to one or lower. 1373 01:30:52.119 --> 01:30:54.359 Antennas that are much too short or too long will 1374 01:30:54.359 --> 01:30:58.000 not work well. We'll have extreme feedpoint impedance causing high 1375 01:30:58.159 --> 01:31:05.840 SWR matching feed line and the load. The antenna impedances 1376 01:31:05.880 --> 01:31:09.560 eliminate standing waves from reflected power and maximize power delivered 1377 01:31:09.560 --> 01:31:13.560 to the load, but not always practical. The impedance matching 1378 01:31:13.640 --> 01:31:15.960 is more often done at the transmitter end of the 1379 01:31:15.960 --> 01:31:21.359 feed line. Devices used to reduce SWR called impedance matchers. 1380 01:31:21.399 --> 01:31:27.079 Transmatch antenna coupler and antenna tuner tuners do not tune 1381 01:31:27.079 --> 01:31:30.880 the antenna at the amplifier thinks it's got a good 1382 01:31:31.119 --> 01:31:34.880 match out there, so in other words, an antenna tuner 1383 01:31:34.920 --> 01:31:38.399 increases the power transfer for the transmitter to the feed line. 1384 01:31:38.439 --> 01:31:41.199 So if you've got a bad antenna, still a bad antenna, 1385 01:31:43.560 --> 01:31:49.319 all right, So impedance matching. These are devices constructed from 1386 01:31:49.640 --> 01:31:54.840 inductors and capacitors that are adjusted by the operator. A 1387 01:31:54.920 --> 01:31:57.479 T circuit can match a wide variety of impedances at 1388 01:31:57.520 --> 01:32:00.079 the feed line connection to fifty homes that matches trans 1389 01:32:00.319 --> 01:32:03.840 output penians. It's important to remember that the SWR in 1390 01:32:03.920 --> 01:32:06.760 the feed line between the impedance matching device and the 1391 01:32:06.760 --> 01:32:10.640 antenna does not change The device just changes the load 1392 01:32:10.800 --> 01:32:18.760 going to the transmitter SWR. The feed line stays the same, okay. 1393 01:32:18.920 --> 01:32:21.159 So if you've got highest WR with your tuner, you've 1394 01:32:21.159 --> 01:32:24.920 still got highest WR on the other side of the tuner, okay. 1395 01:32:25.800 --> 01:32:28.520 But your transmitter is going to put transfer as much 1396 01:32:28.520 --> 01:32:30.760 power as it can to the load. So a T 1397 01:32:30.960 --> 01:32:35.840 network usually consists of two capacitors and in an inductor, 1398 01:32:36.720 --> 01:32:40.239 and then there's a let's see the PI network okay, 1399 01:32:40.279 --> 01:32:43.079 so installed at the transmitter into the feed line. A 1400 01:32:43.199 --> 01:32:46.920 T network is designed to be used with unbalanced coaxial 1401 01:32:46.960 --> 01:32:50.680 feed lines. This circuit uses two variable capacitors and one 1402 01:32:50.760 --> 01:32:55.439 variable inductor. To use balanced feed lines such as window line. 1403 01:32:56.159 --> 01:32:58.760 The output of a T network can be inductively coupled 1404 01:32:58.880 --> 01:33:00.760 to the output, so that need either of the feed 1405 01:33:00.800 --> 01:33:06.960 line conductors is connected to ground. Now, feed line losses 1406 01:33:07.880 --> 01:33:11.720 feed line dissipates a lot of energy, disipates a little 1407 01:33:11.760 --> 01:33:15.479 of the energy that's carried as heat, called attenuation or loss. 1408 01:33:16.319 --> 01:33:18.800 Loss in the feed line is measured in DB's per 1409 01:33:18.920 --> 01:33:22.880 unit of linked, usually specified as dB per hundred feet. 1410 01:33:24.279 --> 01:33:27.319 The loss increases with frequency for all types of feed lines. 1411 01:33:28.159 --> 01:33:32.239 The smaller the cable diameter, the higher the loss. Increasing 1412 01:33:32.359 --> 01:33:35.520 SWR and a feed line also increases the total loss. 1413 01:33:36.640 --> 01:33:39.720 The higher the feed line loss, the lower the measured 1414 01:33:39.800 --> 01:33:43.359 SWR will be at the input to the line. A 1415 01:33:43.439 --> 01:33:46.199 lot of people don't realize how much loss they have 1416 01:33:46.359 --> 01:33:51.880 in their coax feed system. If you've got like we 1417 01:33:52.159 --> 01:33:54.920 I think we had in our earlier talking about about 1418 01:33:54.960 --> 01:33:58.800 dv A one dB loss is you're going to lose 1419 01:33:58.840 --> 01:34:00.880 twenty percent of your power. So if you had one 1420 01:34:00.920 --> 01:34:03.720 hundred watts with the one dB loss in your cable, 1421 01:34:04.119 --> 01:34:07.079 put ad watts to the antenna and you that other 1422 01:34:07.119 --> 01:34:11.520 twenty watts is dissipated as heat in the PAX feed line. Okay, 1423 01:34:12.680 --> 01:34:16.520 so what's the purpose of an antenna tuner? Reduces the 1424 01:34:16.640 --> 01:34:21.960 SWR to the feed line, reduces sw articipation increases power 1425 01:34:22.000 --> 01:34:24.680 transfer from the transmitter to the feed line. It's going 1426 01:34:24.760 --> 01:34:27.560 to be c You may want to think an antenna tuner. 1427 01:34:27.680 --> 01:34:30.000 A lot of people say it reduces the SWR. Well, 1428 01:34:30.760 --> 01:34:34.119 no it doesn't. The antenna and the SWR on the 1429 01:34:34.119 --> 01:34:36.680 other side of the antennaituner. The SWR is still whatever 1430 01:34:36.720 --> 01:34:41.720 it was before, you know. So it just makes the antenna. 1431 01:34:42.680 --> 01:34:46.039 It makes sure antenna allows antenna to transfer as much 1432 01:34:46.039 --> 01:34:50.399 power as it can to the feed line itself. Which 1433 01:34:50.399 --> 01:34:53.159 are the following factors? Determines the characteristic impedance of a 1434 01:34:53.199 --> 01:34:59.399 parallel conductor feed line? See the distance between them b 1435 01:34:59.520 --> 01:35:02.239 A between the centers of the conductors and the radius 1436 01:35:02.239 --> 01:35:07.439 of the conductors themselves. What is the relationship between high 1437 01:35:08.159 --> 01:35:16.000 SWR and transmission line loss uh let's see yep. Highest 1438 01:35:16.119 --> 01:35:22.479 WR increases loss in a lossy transmission line. What is 1439 01:35:22.520 --> 01:35:26.439 the nominal characterist competence of window line transmission line? It's 1440 01:35:26.439 --> 01:35:30.960 about four hundred and fifty oms. What causes reflected power 1441 01:35:31.000 --> 01:35:35.319 at an antenna's feed point that'd be a difference in 1442 01:35:35.359 --> 01:35:38.560 the feed point line impediancy antenna feed point line intendants 1443 01:35:38.840 --> 01:35:43.840 uh an ten of feed pointing impedance, mismatch in impedance. 1444 01:35:45.720 --> 01:35:51.880 How does the attenuation of quaxio cable change with increasing frequency. Okay, 1445 01:35:51.960 --> 01:35:54.600 so the higher the frequency, the more loss you're going 1446 01:35:54.640 --> 01:36:00.359 to have. So intend so the uh antena and is 1447 01:36:00.880 --> 01:36:08.159 TENU increases, so it would be B. And what units 1448 01:36:08.560 --> 01:36:12.800 is RF feed line loss usually expressed? It's usually in 1449 01:36:13.359 --> 01:36:17.600 dB per hundred feet D. What must be done to 1450 01:36:17.640 --> 01:36:20.680 prevent standing waves on a feed line connected to an antenna? 1451 01:36:22.800 --> 01:36:28.479 Not a number, not B, C B D. Antenna feed 1452 01:36:28.479 --> 01:36:31.399 point penis must be matched to the characteristic competence of 1453 01:36:31.439 --> 01:36:35.359 the feed line. If the SWR on an antenna feed 1454 01:36:35.399 --> 01:36:37.720 line is five to one and a matching network at 1455 01:36:37.720 --> 01:36:40.000 the transmitter end of the feed line is adjusted to 1456 01:36:40.000 --> 01:36:44.800 present an SWR one to one to the transmitter, what 1457 01:36:44.880 --> 01:36:47.760 is resulting sw R of the feed line? And it 1458 01:36:47.800 --> 01:36:54.720 would be five to one. So B what standyway ratio 1459 01:36:54.800 --> 01:36:58.039 results from connecting a fifty oero feed line to a 1460 01:36:58.039 --> 01:37:01.239 two hundred er resistant load will be two hundred divided 1461 01:37:01.279 --> 01:37:06.239 by fifty to be four be four to one. What 1462 01:37:06.359 --> 01:37:09.319 sanuay racial results from fifty on feed line to a 1463 01:37:09.439 --> 01:37:13.600 ten ole resistant blode, this case will be fifty divided 1464 01:37:13.640 --> 01:37:16.640 bout ten five to one. All right, now we're going 1465 01:37:16.720 --> 01:37:20.079 to talk about the ionosphere. The sun and scatter modes. 1466 01:37:21.279 --> 01:37:25.560 So the ion a sphere. Uh, it's what's called it's 1467 01:37:25.600 --> 01:37:29.199 the upper reaches of the atmosphere. It gets thinner with distance. 1468 01:37:30.239 --> 01:37:36.319 It begins about thirty miles above the earth. It's remaining 1469 01:37:36.399 --> 01:37:40.600 gases thin, it's enough for ionization to occure. The region 1470 01:37:40.600 --> 01:37:43.960 of the atmosphere becomes very it becomes a very weak conductor. 1471 01:37:44.920 --> 01:37:47.840 And you can see here that it's actually three layers. 1472 01:37:47.840 --> 01:37:51.000 There's a D layer closest to the earth about thirty 1473 01:37:51.039 --> 01:37:54.359 miles up, the E layer, the F one, and the 1474 01:37:54.439 --> 01:37:57.479 F two. The F one and the F two combined 1475 01:37:57.520 --> 01:38:00.319 at night, so it's just one F region at night, 1476 01:38:00.680 --> 01:38:04.239 and the D and E layer disappear at night. Okay, 1477 01:38:04.279 --> 01:38:07.439 So related to the sun, all right. The D layer 1478 01:38:08.159 --> 01:38:12.079 thirty sixty miles is only present when illuminated by the sun. 1479 01:38:13.279 --> 01:38:16.279 It disappears at night because ions and tree electrons are 1480 01:38:16.279 --> 01:38:21.479 close enough together to recombine quickly when no UV is present, 1481 01:38:21.920 --> 01:38:26.000 returning it to a neutral condition. At night, the D 1482 01:38:26.119 --> 01:38:29.039 and E regions disappear, and the F one and F 1483 01:38:29.079 --> 01:38:34.239 two regions combined to form a single F region. Okay, 1484 01:38:35.119 --> 01:38:38.640 So again, the ionosphere consists of several regions of ionized 1485 01:38:38.680 --> 01:38:44.159 particles different heights above the earth. The E layer sixty 1486 01:38:44.199 --> 01:38:48.840 to seventy miles above the earth acts similar to the 1487 01:38:48.920 --> 01:38:53.039 D layer. It's higher and less dense than the D region, 1488 01:38:53.319 --> 01:38:56.760 and it enables it to last a little bit longer 1489 01:38:56.800 --> 01:39:00.880 after sunset. The F layer one hundred three hundred miles 1490 01:39:00.920 --> 01:39:03.279 above is the least dense of the three layers, and 1491 01:39:03.399 --> 01:39:06.880 it remains partially ionized at night. During the day, the 1492 01:39:06.960 --> 01:39:10.399 F one region splits into F one and F two 1493 01:39:11.600 --> 01:39:16.600 during at the height of the F region varies quite 1494 01:39:16.640 --> 01:39:20.199 a bit with local time, season, latitude, and solar activity, 1495 01:39:20.319 --> 01:39:24.520 so it changes based on those things. At any particular location, 1496 01:39:24.640 --> 01:39:28.159 the stronger the illumination from the sun, the higher the 1497 01:39:28.239 --> 01:39:30.960 F two layer will be, so it's maximum height is 1498 01:39:31.000 --> 01:39:37.239 reached at noon, when the sun is overhead and the 1499 01:39:37.279 --> 01:39:44.439 asphere refracts radio waves. It's a weak conductor. Refraction amount 1500 01:39:44.560 --> 01:39:48.359 leads depends on the amount of ionization and wave frequency. 1501 01:39:49.439 --> 01:39:53.479 The higher the ionization, the more the refraction. The lower 1502 01:39:53.560 --> 01:39:58.520 the frequency, the more the refraction, so HF signals relatively 1503 01:39:58.640 --> 01:40:03.079 good refraction are reflected back to the Earth's surface. VHF 1504 01:40:03.119 --> 01:40:09.159 and UHF signals essentially have no refraction. Remember, frequency is 1505 01:40:09.479 --> 01:40:15.479 related to what gets refracted okay VHF okay, So each reflection. 1506 01:40:15.720 --> 01:40:19.319 Each reflection is called the hop and it allows signals 1507 01:40:19.359 --> 01:40:22.039 to be reached hundreds or thousands of miles away. It's 1508 01:40:22.079 --> 01:40:26.640 called skywave propagation via the ionosphere, so it's called skip. 1509 01:40:28.800 --> 01:40:33.840 So skywave propagation via the iosphere is called skip. The 1510 01:40:33.880 --> 01:40:38.800 E layer acts similar to the D layer oop. Sorry 1511 01:40:38.800 --> 01:40:43.319 about that, went to my next chart. The higher the 1512 01:40:43.319 --> 01:40:46.520 region from which the reflection takes place, the longer the hop. 1513 01:40:47.520 --> 01:40:51.199 Waves reflected from F two layer travel at twenty five 1514 01:40:51.279 --> 01:40:55.279 hundred miles before returning to the ground. Hops from the 1515 01:40:55.279 --> 01:41:00.239 E layer a shorter, about twelve hundred miles, and some 1516 01:41:00.319 --> 01:41:04.000 combinations of frequency and iization level result in weak bending. 1517 01:41:05.000 --> 01:41:07.239 The wave must leave the Earth surface at a low 1518 01:41:07.319 --> 01:41:09.479 enough angle for the binding of the wave to be 1519 01:41:09.520 --> 01:41:12.880 sent back. Highest takeoff angle at which a wave can 1520 01:41:12.920 --> 01:41:15.439 be returned to the Earth is called the critical angle. 1521 01:41:16.279 --> 01:41:20.640 Critical angle depends on I spirit ionics, spirit conditions, and frequency. 1522 01:41:24.119 --> 01:41:27.640 Radio waves are reflected and bent in the ion spere, 1523 01:41:27.680 --> 01:41:30.079 so they return to Earth far from the transmitting station. 1524 01:41:30.560 --> 01:41:34.000 Without refraction in the ionosphere, radio waves would pass directly 1525 01:41:34.000 --> 01:41:37.319 into space. So I've got a station over here it's 1526 01:41:37.359 --> 01:41:42.479 transmitting hits the ionosphere at the correct angle and reflected 1527 01:41:42.520 --> 01:41:44.239 back to Earth, and a station on the other side 1528 01:41:44.239 --> 01:41:50.159 of the Earth canton here. If the there's a critical angle, 1529 01:41:50.159 --> 01:41:52.000 we'll talk about the critical angle over here. Waves that 1530 01:41:52.079 --> 01:41:55.119 leads the transmitting antenna above the critical angle are refracted 1531 01:41:55.159 --> 01:41:58.520 in the ionosphere, but not bent towards the return to 1532 01:41:58.560 --> 01:42:02.399 the Earth. It's at and below the critical angle will 1533 01:42:02.439 --> 01:42:06.720 return to Earth. The lowest angle return waves that return 1534 01:42:06.760 --> 01:42:09.560 to the Earth at the greatest distance, which is why 1535 01:42:09.640 --> 01:42:12.640 low angles of radiation are often best for d X stations. 1536 01:42:14.439 --> 01:42:17.119 So depending on how your signal is, the angle of 1537 01:42:17.119 --> 01:42:20.000 which it takes off from your station depends on does 1538 01:42:20.000 --> 01:42:23.359 it get reflected reflected back or not so, and this 1539 01:42:23.439 --> 01:42:29.800 is called the critical angle. Here, the critical angle the 1540 01:42:29.840 --> 01:42:33.720 critical frequency is the highest frequency at which waves transmitted 1541 01:42:33.760 --> 01:42:39.840 straight up will return to Earth. Okay, absorption uh. The 1542 01:42:40.000 --> 01:42:44.000 enemy of propagation is absorption UH. In D and E regions, 1543 01:42:44.039 --> 01:42:47.920 waves passing through the dense the denser gases are partially absorbed. 1544 01:42:48.600 --> 01:42:51.520 The D region is not good is not very good 1545 01:42:51.600 --> 01:42:56.439 at refraction and HF bands below ten megahertz a M 1546 01:42:56.560 --> 01:43:00.000 broadcast bands and at lower frequencies the d region completely 1547 01:43:00.079 --> 01:43:03.479 the absorbs radio waves during the day, preventing those waves 1548 01:43:03.520 --> 01:43:08.000 from returning to Earth. Absorption increases in daytime and when 1549 01:43:08.319 --> 01:43:12.840 solar UV is more intense. When is the best time 1550 01:43:12.880 --> 01:43:17.640 to transmit on HF below ten megaherbs, It's gonna be 1551 01:43:17.640 --> 01:43:21.680 at night and AM radio stations. That's why they can 1552 01:43:21.760 --> 01:43:24.279 run the high power during the day, and when the 1553 01:43:24.319 --> 01:43:27.600 sun goes down they have to reduce their power because 1554 01:43:27.680 --> 01:43:30.279 during the day all their energy is getting absorbed, so 1555 01:43:30.359 --> 01:43:33.680 it's not going other than locally. But at night it 1556 01:43:33.720 --> 01:43:38.079 would it would bounce off the f layer and would 1557 01:43:38.119 --> 01:43:43.119 be it would be a big problem. Noise Noise is 1558 01:43:43.159 --> 01:43:48.520 another enemy of propagation. It covers up weak signals, stronger 1559 01:43:48.560 --> 01:43:53.760 at frequencies below VHF. Lower you go in frequency, the 1560 01:43:53.800 --> 01:43:59.239 stronger the noise or static. It varies seasonally, most noticeably 1561 01:43:59.239 --> 01:44:02.239 on lower frequ the hsvams in the summer, when atmospheric 1562 01:44:02.279 --> 01:44:06.000 noise is the strongest I know around here. In the afternoons, 1563 01:44:06.439 --> 01:44:08.880 a lot of thunderstorms around the area across the state, 1564 01:44:08.960 --> 01:44:16.800 and staticky long path and short path when iyosphere a 1565 01:44:16.880 --> 01:44:20.479 long short path does not support propagation. Sometimes long path 1566 01:44:20.520 --> 01:44:24.960 will occasionally propagation over long and short paths will be 1567 01:44:25.000 --> 01:44:28.920 supported at the same time. Unless the paths are almost equal, 1568 01:44:28.960 --> 01:44:31.279 there will be an echo or delayed. Signal arrives a 1569 01:44:31.520 --> 01:44:35.760 fraction of a second later. In my experience, I've done 1570 01:44:35.840 --> 01:44:38.239 this a couple of times. I've heard my signal go 1571 01:44:38.479 --> 01:44:41.279 short and long path and there is a little echo delay. 1572 01:44:41.319 --> 01:44:43.520 It's a cool thing that happens, and you get all 1573 01:44:43.520 --> 01:44:45.880 excited about it. But it's a pretty cool. It's amazing 1574 01:44:45.880 --> 01:44:49.680 phenomena around the world propagation. You can hear your own 1575 01:44:49.720 --> 01:44:52.039 signal coming all the way around your location about one 1576 01:44:52.119 --> 01:44:55.760 seventh of a second later, So conditions are right. It's 1577 01:44:55.800 --> 01:44:59.399 a pretty cool thing. And this catch shows the Earth 1578 01:45:00.239 --> 01:45:04.039 both has both great circle paths drawn between the two stations. 1579 01:45:04.960 --> 01:45:08.439 So here I've got this is your station, and you 1580 01:45:08.520 --> 01:45:10.600 transmit and it goes all the way around the Earth 1581 01:45:10.640 --> 01:45:15.319 and comes to that station or short path is here, 1582 01:45:15.479 --> 01:45:17.479 this is long path, and this would be short path 1583 01:45:17.640 --> 01:45:20.600 this way, And like I said, sometimes I can hear 1584 01:45:21.520 --> 01:45:23.399 you can hear your signal come all the way back around. 1585 01:45:23.560 --> 01:45:30.520 Kind of cool. Okay, how is a directional antenna pointed 1586 01:45:31.600 --> 01:45:34.600 when making a long path contact with that other station, 1587 01:45:36.319 --> 01:45:38.760 it would be one hundred eight degrees from the station's 1588 01:45:38.760 --> 01:45:42.960 short path. See like, if I'm trying to go here 1589 01:45:43.000 --> 01:45:46.840 to Texas, I point towards the I guess towards the west. 1590 01:45:47.399 --> 01:45:49.640 If I'm trying to for a short path for long paths, 1591 01:45:49.720 --> 01:45:51.560 I point towards the east. If I can come all 1592 01:45:51.560 --> 01:45:55.159 the way back around. What is a characteristic of skywave 1593 01:45:55.279 --> 01:45:58.119 signals arriving at your location by both short path and 1594 01:45:58.199 --> 01:46:04.399 long path. Let's see periodic feeling its light echo might 1595 01:46:04.439 --> 01:46:09.479 be heard d. What is the approximate maximum distance along 1596 01:46:09.520 --> 01:46:13.680 the Earth's surface normally covered on one hop using the 1597 01:46:13.800 --> 01:46:17.399 F two layer, It's about twenty five hundred miles C. 1598 01:46:18.520 --> 01:46:22.680 What is the approximate link distance of the Earth's surface 1599 01:46:22.720 --> 01:46:25.800 normally for one hop using the E region, It's about 1600 01:46:25.880 --> 01:46:30.920 twelve hundred D. What ion expirent region is closest to 1601 01:46:30.960 --> 01:46:35.720 the Earth's surface That would be the D region. Ay, 1602 01:46:37.239 --> 01:46:39.439 what is meant by the term critical frequency out of 1603 01:46:39.439 --> 01:46:44.880 given incident angle highest frequency which is reflected back to Earth? 1604 01:46:45.119 --> 01:46:50.680 That is the answer? Hey, why is skip propagation via 1605 01:46:50.720 --> 01:46:53.960 the F two region longer than via the other I 1606 01:46:54.199 --> 01:47:02.960 experienced regions densis highest because it's the highest c's the 1607 01:47:03.159 --> 01:47:05.399 F two layer is the highest layer that we have 1608 01:47:05.560 --> 01:47:09.840 is the furthest away. So what does the term critical 1609 01:47:09.880 --> 01:47:16.720 angle mean as applied to radio wave propagation paths? It 1610 01:47:16.720 --> 01:47:19.600 would be d the highest takeoff angle that will turn 1611 01:47:19.640 --> 01:47:24.800 the radio wave to Earth under specific ionospirit conditions. There 1612 01:47:24.920 --> 01:47:26.920 websites you can go to during the day that give 1613 01:47:26.960 --> 01:47:32.640 you critical angle and frequency and changes of course as 1614 01:47:32.640 --> 01:47:35.640 the sun changes, as there are places you can go 1615 01:47:35.680 --> 01:47:39.800 look at the propagation. Why is a long distance communication 1616 01:47:39.880 --> 01:47:41.880 on forty sixty eighty and one hundred and sixty years 1617 01:47:41.920 --> 01:47:46.439 more difficult during the day. That's because it gets absorbed 1618 01:47:46.439 --> 01:47:53.680 by the D region c O, which ionic sphirit region 1619 01:47:53.840 --> 01:47:57.439 is the most absorbent of signal levels below ten megahertz 1620 01:47:57.560 --> 01:48:04.800 during daylight hours. That would be the D region. Okay, 1621 01:48:04.880 --> 01:48:08.520 sunspots and sun cycle, let's talk about the sun. I 1622 01:48:08.560 --> 01:48:11.840 Hones sphere is dependent on solar UV to separate electrons 1623 01:48:11.880 --> 01:48:15.479 from atoms. Much of the variation in UV radiation is 1624 01:48:15.560 --> 01:48:19.920 due to sunspot activity. One complete sunspot cycle lasts about 1625 01:48:19.960 --> 01:48:24.680 eleven years, when more sunspots are observed more UV is 1626 01:48:24.760 --> 01:48:29.039 being generated, creating more intense ionization, improving propagation on higher 1627 01:48:29.079 --> 01:48:32.560 frequency bands above ten megahertz and even into the lower 1628 01:48:32.680 --> 01:48:39.079 VHF region. Here's a graph that shows the sunspot cycles 1629 01:48:39.119 --> 01:48:42.640 over time, and E said, it's about eleven year cycle. 1630 01:48:44.039 --> 01:48:47.640 We've just come off. I guess our peak cycle, and 1631 01:48:47.960 --> 01:48:52.600 it's been it's been fund in mid twenty twenty three 1632 01:48:52.840 --> 01:48:55.239 when this book was published, cycle twenty five was heating 1633 01:48:55.319 --> 01:48:57.279 up and propagation on ten years and other bands was 1634 01:48:57.319 --> 01:49:04.039 increasing at peak cycle. There may be sufficient solar UV 1635 01:49:04.239 --> 01:49:07.319 to cause higher frequency bands ten meters, for example, to 1636 01:49:07.319 --> 01:49:11.880 stay open for long distances during contacts at night. High 1637 01:49:11.920 --> 01:49:16.680 ionization negatively impacts low frequency bands age sixty meters because 1638 01:49:16.680 --> 01:49:21.439 it increases absorption when solar activity is low. Lower HF 1639 01:49:21.479 --> 01:49:25.319 bands have good propagation, and higher HF bands above twenty 1640 01:49:25.359 --> 01:49:30.199 megaherts fifteen meters and up often are often closed. One 1641 01:49:30.239 --> 01:49:32.119 band that seems to do well at all times and 1642 01:49:32.279 --> 01:49:37.720 sunspot cycles is twenty meters fourteen megaherts. It supports daytime 1643 01:49:37.760 --> 01:49:42.039 communication worldwide nearly every day, and that's true twenty meters 1644 01:49:42.079 --> 01:49:46.039 you can always almost always find something going on twenty 1645 01:49:46.079 --> 01:49:50.239 meters seems to be the sweet spot. And here's a 1646 01:49:50.319 --> 01:49:55.640 chart showing the propagation on the different bands. What happens 1647 01:49:55.720 --> 01:50:00.640 during the day, what happens during nighttime. So the bands 1648 01:50:00.680 --> 01:50:03.479 I mean dear deer during the day, the low the 1649 01:50:03.520 --> 01:50:08.479 low bands are fairly quiet. You can do regional communications 1650 01:50:09.439 --> 01:50:14.239 in the state of Alabama. We can talk regionally. Uh, 1651 01:50:14.600 --> 01:50:17.079 when we're doing our areas activities during the day, we 1652 01:50:17.119 --> 01:50:23.439 can can usually community we can communicate. So based on 1653 01:50:23.479 --> 01:50:27.039 the time of day and the band you're on. And 1654 01:50:27.439 --> 01:50:29.760 once you get your general license and start getting to 1655 01:50:29.840 --> 01:50:33.319 the operate on the HF bande, you're gonna learn all 1656 01:50:33.399 --> 01:50:36.359 these things here. You're gonna experience them. You're going to 1657 01:50:36.399 --> 01:50:40.159 become an expert on propagation, when to when to communicate, where, 1658 01:50:40.199 --> 01:50:45.199 what bands are good. It's a whole lot of fun. Okay. 1659 01:50:45.399 --> 01:50:48.039 Sun spot's also seem to move across the Sun's surface 1660 01:50:48.079 --> 01:50:51.399 because the Sun rotates once every twenty eight days. That 1661 01:50:51.520 --> 01:50:54.600 is why propagation conditions good and bad on the HF 1662 01:50:54.640 --> 01:50:57.199 bands often repeat themselves in a twenty eight day cycle 1663 01:50:57.560 --> 01:51:04.560 as sunspots rotate back into the From Earth. Measuring the 1664 01:51:04.600 --> 01:51:09.640 solar activity, you can there's a you can measure the 1665 01:51:09.760 --> 01:51:13.359 number of suns of sunspots. There's a thing called the 1666 01:51:13.399 --> 01:51:17.279 solar flux index. It describes the amount of twenty eight 1667 01:51:17.439 --> 01:51:23.560 hundred megahertz radio energy. High levels indicate high solar activity 1668 01:51:23.560 --> 01:51:26.920 and better HF propagation of O ten megahertz. A thing 1669 01:51:27.000 --> 01:51:30.199 called the K index has a value from zero to nine. 1670 01:51:30.279 --> 01:51:33.319 It represents the short term stability of the Earth's magnetic 1671 01:51:33.439 --> 01:51:38.800 or geomagnetic field. Higher values indicate geomagnetic field is disturbed, 1672 01:51:38.840 --> 01:51:42.800 which disrupts HF. An a index gives a good picture 1673 01:51:42.800 --> 01:51:46.000 of long term geomagnetic field stability, and it ranges from 1674 01:51:46.079 --> 01:51:50.199 zero stable to four hundred greatly disturbed. It's calculated from 1675 01:51:50.239 --> 01:51:52.840 the K index. And there are sites you can go 1676 01:51:52.920 --> 01:52:00.119 to that have this informational real time And so LOO 1677 01:52:00.159 --> 01:52:02.960 activity is so important to propagation and communication that is 1678 01:52:03.039 --> 01:52:06.000 monitored constantly. And like I said, you can go to 1679 01:52:06.079 --> 01:52:09.239 certain websites and get these values and the information on 1680 01:52:09.279 --> 01:52:14.680 the sun. Okay, So, how does a higher sunspot number 1681 01:52:14.760 --> 01:52:22.600 affect h of propagation and answers? A higher sunspot number 1682 01:52:22.720 --> 01:52:27.359 generally indicate a greater probability of good propagation at higher frequencies. 1683 01:52:28.680 --> 01:52:31.199 Which is the following are least reliable for long distance 1684 01:52:31.239 --> 01:52:36.000 communications during periods of lower solar activity. That would be 1685 01:52:36.199 --> 01:52:40.760 fifteen meters, twelve and ten. That's what we've got, So 1686 01:52:41.079 --> 01:52:45.199 we've got low solar activity higher bands. What is the 1687 01:52:45.199 --> 01:52:50.079 solar flux index? It is the measure of the solar 1688 01:52:50.159 --> 01:52:53.560 radiation at the ten point one seven centimeter wavelength band. 1689 01:52:55.880 --> 01:52:58.439 At what point is the solar cycle? Does the twenty 1690 01:52:58.439 --> 01:53:02.760 meter ban usually support or worldwide propagation during daylight hours? 1691 01:53:04.039 --> 01:53:07.600 Usually it's all the time. D It's truly not affect. 1692 01:53:07.640 --> 01:53:10.479 I mean, it's effective, but it usually does fairly well. 1693 01:53:10.760 --> 01:53:12.880 Twenty meters of the place you can usually go to 1694 01:53:13.000 --> 01:53:16.000 and find some activity no matter what time of day. 1695 01:53:16.880 --> 01:53:20.159 What causens HF propagation conditions are very periodically at a 1696 01:53:20.199 --> 01:53:23.199 twenty six to twenty eight day cycle, and that would 1697 01:53:23.239 --> 01:53:27.920 be the rotation of the Sun's surface layers around its axis. C. 1698 01:53:29.960 --> 01:53:34.960 What does the K index measure? It measures the short 1699 01:53:35.039 --> 01:53:40.039 term stability of the Earth's magnetic field. What does the 1700 01:53:40.079 --> 01:53:44.960 ax A index measures? And it's the long term stability 1701 01:53:45.000 --> 01:53:50.399 of the Earth's geomagnet field. Which of the following is 1702 01:53:50.439 --> 01:53:55.479 typical of the lower hf frequencies during the summer, let's 1703 01:53:55.520 --> 01:53:59.119 see high levels of atmospheric noise and static I think 1704 01:53:59.159 --> 01:54:03.399 that that is correct. Okay, so let's let's talk about 1705 01:54:03.439 --> 01:54:09.359 propagation some terms. There's a maximum usable frequency called MUFF. 1706 01:54:10.279 --> 01:54:13.800 It's the highest frequency of which propagation exists between two points. 1707 01:54:14.640 --> 01:54:19.119 The lowest usable frequency l UF. Waves below the LUF 1708 01:54:19.199 --> 01:54:23.520 will be completely absorbed by the ionis frequent by the ionosphere. 1709 01:54:24.439 --> 01:54:28.960 MUFF and LUFF depend on specific data between two points, locations, 1710 01:54:28.960 --> 01:54:32.119 and distance apart. It varies with the time of day, 1711 01:54:32.239 --> 01:54:37.560 seasonal amount of solar radiation, and ionosphere stability. Operating near 1712 01:54:37.600 --> 01:54:41.319 the maximum usual frequency often gives excellent results. Absorption is 1713 01:54:41.359 --> 01:54:46.399 lowest just below it, one may One way to check 1714 01:54:46.520 --> 01:54:51.000 actual conditions is to listen for propagation beacons. Some provide 1715 01:54:51.039 --> 01:54:54.720 real time propagation information. Many stations between twenty eight point 1716 01:54:54.760 --> 01:54:57.560 one nine and twenty eight point two five megahertz that 1717 01:54:57.640 --> 01:55:01.279 are excellent are excellent sources of information about ten meter propagation. 1718 01:55:02.760 --> 01:55:05.000 To make contact with the distance station, you will have 1719 01:55:05.079 --> 01:55:08.119 to use a frequency between LUF and MUF, so the 1720 01:55:08.159 --> 01:55:10.760 wave has been back toward the Earth but isn't absorbed 1721 01:55:11.520 --> 01:55:14.520 if the MUF drops below the LUF, then no propagation 1722 01:55:14.680 --> 01:55:18.520 exists between those two points via ordinary skywave. And there's 1723 01:55:19.840 --> 01:55:23.279 on the on the web you can go find maps 1724 01:55:23.319 --> 01:55:26.920 of the world that show the muff and the luff 1725 01:55:27.039 --> 01:55:30.960 and it's got what the propagation is between different points 1726 01:55:30.960 --> 01:55:33.079 on the Earth and the bands that are open, and 1727 01:55:33.840 --> 01:55:37.560 a lot of good information out there. Okase talk about 1728 01:55:37.560 --> 01:55:42.079 solar disturbances. Approximately eight minutes after a solar flare occurs 1729 01:55:42.119 --> 01:55:45.720 on the Sun, the ultraviolet and X ray radiation released 1730 01:55:45.760 --> 01:55:49.520 by the flare reaches the Earth. This radiation causes increased 1731 01:55:49.520 --> 01:55:56.359 ionization and radio wave absorption in the d region. A 1732 01:55:56.399 --> 01:55:59.319 solar flare, which is a large eruption of energy and 1733 01:55:59.439 --> 01:56:02.840 solar mature. When magnetic field disruptions occur on the surface 1734 01:56:03.119 --> 01:56:06.439 of the of a solar flare, there is a large 1735 01:56:06.560 --> 01:56:10.600 eruption of energy and solar material when magnetic field disruptions 1736 01:56:10.600 --> 01:56:16.119 occur on the surface of the Sun. A coronal hole, 1737 01:56:16.239 --> 01:56:18.479 which is a weak area in the Sun's corona the 1738 01:56:18.520 --> 01:56:22.720 outer layer through which plasma, ionized gas, and charged particles 1739 01:56:22.800 --> 01:56:26.359 escape the Sun's magnetic field and streams away into space 1740 01:56:26.399 --> 01:56:30.640 at high velocities. A coronal mass ejection CME is an 1741 01:56:30.640 --> 01:56:36.359 ejection of large amounts of material from the corona, and 1742 01:56:36.520 --> 01:56:44.279 all of these disrupt HF propagation some sudden ionosphere disturbances 1743 01:56:44.439 --> 01:56:47.760 UV and X ray radiation from a solar flare travels 1744 01:56:47.760 --> 01:56:51.079 at the speed of light to impact the ionosphere about 1745 01:56:51.079 --> 01:56:54.239 eight minutes later. When radiation hits the ionosphere, the level 1746 01:56:54.279 --> 01:56:58.640 of ionization increases rapidly, particularly in the D region. This 1747 01:56:58.720 --> 01:57:03.720 increases absorption from causing a sudden ionospheric disturbance, also known 1748 01:57:03.760 --> 01:57:08.880 as a radio blackout. Lower bands are more strongly affected, 1749 01:57:08.880 --> 01:57:12.119 but communication may still be possible on a higher band. 1750 01:57:14.079 --> 01:57:18.000 Sudden anospheric disturbances affect only the sunlit side of the Earth. 1751 01:57:18.159 --> 01:57:25.680 The dark side communications may be relatively unaffected. Geomagnetic disturbances. 1752 01:57:26.119 --> 01:57:29.319 This is the interaction between solar wind and geomagnetic field, 1753 01:57:29.560 --> 01:57:34.279 which creates a region of space called the magnetosphere. Charged 1754 01:57:34.319 --> 01:57:38.880 particles from coronal poles and coronal mass ejections travel considerably 1755 01:57:38.920 --> 01:57:41.920 slower and take longer to reach the Earth about fifteen 1756 01:57:41.960 --> 01:57:46.159 to forty hours. These particles deposit their energy into Earth's 1757 01:57:46.199 --> 01:57:50.760 geomagnetic field and increase ionization in the E region, causing 1758 01:57:51.000 --> 01:57:55.399 oral displays and creating a geomagnetic storm, which affects higher 1759 01:57:55.560 --> 01:58:00.880 HF bands. First, long distance pass that traverse high latitudes, 1760 01:58:00.920 --> 01:58:03.479 particularly those that pass near the magnetic poles, may be 1761 01:58:03.520 --> 01:58:08.960 completely wiped out for days, for hours or days, and 1762 01:58:09.000 --> 01:58:12.760 these can create auroras that reflect radio waves above twenty megahertz. 1763 01:58:13.439 --> 01:58:16.800 Auroral propagation is strongest on six meters and two meters, 1764 01:58:17.239 --> 01:58:21.760 modulating the signals with the hiss or buzz, so sometimes 1765 01:58:21.800 --> 01:58:24.119 you can actually hear it on the signals. There's a 1766 01:58:24.159 --> 01:58:27.720 modulation that happens. It's kind of cool effect. So here's 1767 01:58:27.720 --> 01:58:31.760 some questions. What effect does a sudden honest spirit disturbance 1768 01:58:31.840 --> 01:58:38.000 have on the daytime iono spirit propagation b It disrupts 1769 01:58:38.000 --> 01:58:42.880 signals on low frequencies more than those on higher frequencies. Approximately, 1770 01:58:42.920 --> 01:58:47.239 how long does it take for increase ultra ultra violet 1771 01:58:47.399 --> 01:58:52.199 X radiation from solar flares to reflect radio propagation on Earth? 1772 01:58:53.199 --> 01:58:59.399 About eight minutes? And what is a geomagnetic storm. It's 1773 01:58:59.439 --> 01:59:03.840 a temporary disturbance in the Earth's geomagnetic field that bed 1774 01:59:04.760 --> 01:59:09.800 How can a geomagnetic storm affect HF propagation It degrades 1775 01:59:09.880 --> 01:59:15.840 high latitude HF propagation. How can geomagnetic activity benefit radio 1776 01:59:15.920 --> 01:59:22.199 communications by creating a roar as that can reflect VHF signals. 1777 01:59:23.720 --> 01:59:25.840 How long does it take a coronal mass ejection to 1778 01:59:25.880 --> 01:59:31.439 affect radiopropagation on Earth? Usually it's about fourteen hours to 1779 01:59:31.520 --> 01:59:37.680 several days. It just depends. How is long distance radio 1780 01:59:37.680 --> 01:59:41.319 communication usually affected by the charged particles that reach Earth 1781 01:59:41.359 --> 01:59:51.199 from solar chronal holes HF communication is disturbed? What factors 1782 01:59:51.279 --> 01:59:56.199 affect the muff? Just a maximum usable frequency, path distance, 1783 01:59:56.319 --> 02:00:00.439 time of day, solar ardiation, all of those affected. Maximum 1784 02:00:00.479 --> 02:00:04.880 usual frequency is which frequency will have at least have 1785 02:00:04.960 --> 02:00:09.960 the least attenuation For long distance skip propagation, that would 1786 02:00:10.000 --> 02:00:15.720 be just below the maximum usable frequency. Once of the 1787 02:00:15.720 --> 02:00:18.399 following is a way to determine current propagation on a 1788 02:00:18.439 --> 02:00:24.319 desired ban from your station. Use a network of automated 1789 02:00:24.439 --> 02:00:27.560 receiving stations on the Internet to see where your transmissions 1790 02:00:27.560 --> 02:00:29.800 are and being received, because it's different all over the 1791 02:00:29.840 --> 02:00:33.199 worth all over the world given at a given time, 1792 02:00:33.359 --> 02:00:36.279 So check a network and see what the see what's 1793 02:00:36.279 --> 02:00:40.920 the receiving stations showing at a particularly given time. How 1794 02:00:40.920 --> 02:00:43.880 does say honest sphere effect radio waves with frequencies below 1795 02:00:43.920 --> 02:00:48.039 them up and above their gluffs. Yeah, they are refracted 1796 02:00:48.079 --> 02:00:52.279 back to Earth. What usually happens to radio waves with 1797 02:00:52.399 --> 02:00:57.079 frequencies below the LUF They are attenuated before reaching the 1798 02:00:57.119 --> 02:01:02.359 destination so to get through. What does LOUFF stand for? 1799 02:01:03.640 --> 02:01:11.600 It's the lowest usable frequency for communication between two specific points. Okay, 1800 02:01:11.960 --> 02:01:15.680 What does MUFF stand for? It's the maximum usable frequency 1801 02:01:16.000 --> 02:01:20.560 between two points, right? And what does what happens to 1802 02:01:20.720 --> 02:01:27.760 HF propagation when the luff exceeds the muff? Propagation is 1803 02:01:27.840 --> 02:01:33.119 not possible over that path? That's correct, all right? Talk 1804 02:01:33.119 --> 02:01:38.239 about some scatter modes, some terms called backscatter, that's reflections 1805 02:01:38.279 --> 02:01:42.119 from the from from features on the Earth's surface. Waves 1806 02:01:42.119 --> 02:01:45.119 can also be scattered from within the IONO sphere, allowing 1807 02:01:45.119 --> 02:01:47.720 signals to be heard from stations too distant to be 1808 02:01:47.800 --> 02:01:50.840 heard by ground wave and on on frequencies too high 1809 02:01:50.880 --> 02:01:55.760 for short for short hop skywave propagation, scatter and backscatter 1810 02:01:55.880 --> 02:01:59.319 helped fill in the skip zone where signals would otherwise 1811 02:01:59.359 --> 02:02:03.239 not be heard. Signals received via HF scatter are usually 1812 02:02:03.239 --> 02:02:07.840 weaker than those received by normal skyway propagation. Reflection is 1813 02:02:07.880 --> 02:02:11.000 not very efficient and tends to spread out the signal. 1814 02:02:11.520 --> 02:02:17.399 Such such signals sound disturbed, sound storted, resulting in fluttering 1815 02:02:17.520 --> 02:02:25.159 or wavering. I'm striking the ground. After ionosphere reflection, radio 1816 02:02:25.199 --> 02:02:29.439 waves may be reflected back towards the transmitting station. Backscatter 1817 02:02:29.560 --> 02:02:32.880 consists of signals reflected by the ground back into the 1818 02:02:32.920 --> 02:02:38.039 skip zone. Backscatter supports communication between stations that would otherwise 1819 02:02:38.479 --> 02:02:41.279 be in each other's be in each other's skip zone. 1820 02:02:43.039 --> 02:02:46.119 So I've got a signal, I've got a h I've 1821 02:02:46.119 --> 02:02:49.520 got a station transmitting here, and I've got another receiving station. 1822 02:02:49.680 --> 02:02:53.600 He's out of my skip zone. But because of some backscatter, 1823 02:02:54.000 --> 02:02:57.439 some of that is actually received by this particular station. 1824 02:02:57.680 --> 02:02:59.760 So the skip distance he's too far, he's out of 1825 02:02:59.800 --> 02:03:03.920 my skip zone. But scattered signals from the ionosphere, he 1826 02:03:04.000 --> 02:03:06.319 can sometimes hear me. And usually those are weak signals 1827 02:03:06.359 --> 02:03:08.479 and they're fluttery, but he can. That's a that's a 1828 02:03:08.520 --> 02:03:13.600 way he can. He can. I can communicate it near 1829 02:03:13.720 --> 02:03:17.520 vertical incident skywave in VIZ. We just talked about what's 1830 02:03:17.560 --> 02:03:19.800 the INVIS, what what are How we can build an 1831 02:03:19.960 --> 02:03:24.640 VIZ and invis antenna for signal below the critical frequency 1832 02:03:24.680 --> 02:03:28.479 the ionosphere reflects waves arriving at the angle even vertical 1833 02:03:29.000 --> 02:03:33.720 always above five megahertz up to forty meters in VIZ 1834 02:03:34.000 --> 02:03:36.720 is for a signal below the critical frequency when it 1835 02:03:36.920 --> 02:03:40.680 when it is radiated vertically, the reflected scatters the signal 1836 02:03:40.760 --> 02:03:43.720 back to Earth through the region of up to two 1837 02:03:43.800 --> 02:03:46.760 hundred to three hundred miles. To make use of INVIZ, 1838 02:03:46.840 --> 02:03:49.880 horizontally polarized dipoles are placed low to the ground so 1839 02:03:49.920 --> 02:03:53.800 that the radiation pattern is almost omnidirectional and concentrated at 1840 02:03:53.880 --> 02:04:00.159 high elevation angles near vertical incident skywave INVEZ communication and 1841 02:04:00.359 --> 02:04:03.880 relies on signals below the critical frequency transmitted at high 1842 02:04:03.920 --> 02:04:08.079 vertical angles. The signals are reflected by the aosphere back 1843 02:04:08.119 --> 02:04:12.960 to Earth in the region around the transmitter. So here's 1844 02:04:12.960 --> 02:04:17.399 an example. I've got a transmitting station here. I've got 1845 02:04:17.399 --> 02:04:19.039 a guy on the other side of this mountain. I 1846 02:04:19.039 --> 02:04:21.520 can't talk to him directly, but I can bounce the 1847 02:04:21.560 --> 02:04:25.680 signal off the iosphere and get to him. And you're 1848 02:04:25.760 --> 02:04:28.840 using the F layer to do this. H transmit this 1849 02:04:29.720 --> 02:04:35.840 these reflections. Hey, what's the effect of HF scattered? So 1850 02:04:36.079 --> 02:04:40.560 was the characteristic of HF scattered? Uh? They have a 1851 02:04:40.600 --> 02:04:45.399 fluttery sound. Uh, usually weaker signals. What makes HF scatter 1852 02:04:45.479 --> 02:04:51.800 signals often sound distorted? It's because there it's it's scattered 1853 02:04:51.880 --> 02:04:56.479 to the zip code, the zip zone along several paths. Okay, 1854 02:04:57.479 --> 02:05:00.920 Why are HF scattered signals in the skip zone usually weak? 1855 02:05:02.479 --> 02:05:04.439 That's because only a small part of the signal is 1856 02:05:04.760 --> 02:05:10.680 scattered back into the skip zone. What type of propagation 1857 02:05:11.000 --> 02:05:14.840 allows signals to be heard in the transmitting station skip 1858 02:05:14.920 --> 02:05:21.720 zone that would be scattered? What is a near vertical 1859 02:05:21.720 --> 02:05:31.680 incident skywave propagation and that is short distance MF or 1860 02:05:31.840 --> 02:05:36.039 HF propagation using high elevation angles. Okay, our next section, 1861 02:05:36.159 --> 02:05:39.399 we're going to talk about electrical safety, RF exposure and 1862 02:05:39.520 --> 02:05:44.039 outdoor safety. So, first of all, talking about electrical safety, 1863 02:05:44.439 --> 02:05:48.640 preventing electrical shock. Always have a master on off switch 1864 02:05:48.720 --> 02:05:52.600 for station and workbench, clearly labeled and somewhat away from 1865 02:05:52.600 --> 02:05:56.079 the equipment. Don't put yourself in a position to be 1866 02:05:56.079 --> 02:06:01.359 shocked when working inside equipment, Remove insulate or secure loose 1867 02:06:01.399 --> 02:06:05.520 wires and cables, and use a ground stick to remove 1868 02:06:05.640 --> 02:06:12.239 charge from capacitors. So, I see, what's a groundstick? Well, yeah, 1869 02:06:12.239 --> 02:06:14.600 here we go. Here's a ground stick ground stick is 1870 02:06:15.720 --> 02:06:18.640 a ground stick. It's touched to all circuitry inside an 1871 02:06:18.680 --> 02:06:21.239 enclosure to ensure that that no high voltage is present. 1872 02:06:21.600 --> 02:06:24.479 The alligator clip is attached to an electrical ground and 1873 02:06:24.520 --> 02:06:27.680 the eyebolt sput on a on a contact with the 1874 02:06:27.720 --> 02:06:30.960 circuit So you've got an insulating piece of PBC pipe 1875 02:06:31.520 --> 02:06:35.960 and this allows you to touch certain components and discharge 1876 02:06:36.000 --> 02:06:41.840 them to the potential of the gap itself. So what's 1877 02:06:41.840 --> 02:06:44.079 the effects of electrical current through the human body on 1878 02:06:44.119 --> 02:06:48.199 an average person? Well below a millionamp generally you can't 1879 02:06:48.239 --> 02:06:53.399 perceive it. One million amp bank tingle, five million amps 1880 02:06:54.319 --> 02:06:59.840 slight shock six to twenty five million ams painful for women, 1881 02:07:00.119 --> 02:07:04.479 nine to thirty painful for men. Just the freezing you 1882 02:07:04.520 --> 02:07:07.600 can't let that SIT's in the let go range fifty 1883 02:07:07.640 --> 02:07:12.079 one hundred and fifty million amps very painful, and this 1884 02:07:12.239 --> 02:07:15.880 is if you had contact. You know, inside the body, 1885 02:07:16.159 --> 02:07:21.920 your skin is a resistance, so that helps, but it 1886 02:07:21.960 --> 02:07:24.159 can be very painful. So it doesn't take much current 1887 02:07:24.279 --> 02:07:30.479 to cause problems with the human body. Solder in safety 1888 02:07:30.640 --> 02:07:34.920 so primarily solder is primarily lead based. Ten is added 1889 02:07:34.920 --> 02:07:37.880 to lower the melting point. Lead is a known toxin. 1890 02:07:38.680 --> 02:07:43.800 Always solder in a well ventilated area. Rosin flux smoke 1891 02:07:44.159 --> 02:07:47.079 is likely not good for you in high doses. Use 1892 02:07:47.119 --> 02:07:49.960 a well ventilated area if you can. When finished, wash 1893 02:07:50.000 --> 02:07:53.720 your hands, remove solder or flux residue. As of two 1894 02:07:53.720 --> 02:07:57.079 thousand and six, environmental regulations were passed for solder to 1895 02:07:57.119 --> 02:08:01.840 eventually be lead free. Leaded soft are still available. Lead 1896 02:08:01.840 --> 02:08:06.239 free sawder melts at significantly higher temperatures than traditional sixty 1897 02:08:06.239 --> 02:08:11.720 to forty solder. Greater risk of damage to heat sensitive 1898 02:08:11.720 --> 02:08:14.920 components because you got to you've got to run a 1899 02:08:14.960 --> 02:08:19.680 little higher temperature. So what's the following is a danger 1900 02:08:19.680 --> 02:08:26.079 for lead tin solder. Lead tin can contaminate food in 1901 02:08:26.119 --> 02:08:30.800 your hands. Carefully, Hey, carefully, you know, wash your hands 1902 02:08:30.840 --> 02:08:36.920 after you've handled lead tin solder. Okay, Wiring practices National 1903 02:08:36.960 --> 02:08:40.520 Electrical Code Handbook contains the details for handling AC wiring 1904 02:08:40.560 --> 02:08:44.159 and the home in the station. Use your local building 1905 02:08:44.199 --> 02:08:46.640 codes ensure that home is properly wired to meet special 1906 02:08:46.680 --> 02:08:52.439 local conditions. You standard wire color conventions. Hot which is 1907 02:08:52.520 --> 02:08:56.119 red or black insulation it's connected to the brass terminal, 1908 02:08:56.239 --> 02:09:00.960 or screw neutral, which is white insulation is connected to 1909 02:09:01.000 --> 02:09:05.000 the silver terminal. Or screw, and green your ground. Ground 1910 02:09:05.119 --> 02:09:08.079 is your green insulation or bare wires connected to the 1911 02:09:08.079 --> 02:09:11.680 green or bear terminal screw. So those are the standard 1912 02:09:11.720 --> 02:09:16.840 wiring AC wiring conventions use in your home. Don't run 1913 02:09:16.880 --> 02:09:19.920 antenna feed lines overpower lines or service drops from a 1914 02:09:19.960 --> 02:09:26.840 transformer to the house. Here's some standard wiring conventions. Standard 1915 02:09:26.840 --> 02:09:30.279 wiring for outlets, one hundred and twenty and two hundred 1916 02:09:30.319 --> 02:09:34.680 old AC plugs and receptacles. It's crrectally important to follow 1917 02:09:34.680 --> 02:09:39.159 the correct wiring techniques for AC wiring. The white wires 1918 02:09:39.199 --> 02:09:42.039 neutral green wire is ground, and the red or black 1919 02:09:42.079 --> 02:09:44.840 wire is the hot lead. Note that two hundred and 1920 02:09:44.840 --> 02:09:48.920 forty volt circuits may have two hot wires and the ground, 1921 02:09:49.279 --> 02:09:55.239 so be careful when you wiring things are hooking things up, 1922 02:09:55.840 --> 02:10:02.119 observe the wire colors and the correct connections. AC wiring 1923 02:10:02.159 --> 02:10:05.079 most common sizes are number twelve gauge for twenty amp 1924 02:10:05.119 --> 02:10:10.920 circuits and fourteen gauge for fifteen amp circuits. Use fuse 1925 02:10:11.000 --> 02:10:13.439 or circuit breakers for the hot conductor for one hundred 1926 02:10:13.439 --> 02:10:15.800 and twenty bolt circuits on both hot and use them 1927 02:10:15.840 --> 02:10:17.920 on both for the hot conductors. On a two hundred 1928 02:10:17.920 --> 02:10:22.079 and forty bolt circuit which uses the three or four wires. 1929 02:10:24.239 --> 02:10:28.439 All right, here's the here's some current capacity ratings for 1930 02:10:28.600 --> 02:10:32.960 some common wire sizes. The rating of a wire to 1931 02:10:33.039 --> 02:10:36.560 carry current is called this opacity. When you are finished 1932 02:10:36.680 --> 02:10:39.039 wiring the job, verify that you have the connect correct 1933 02:10:39.079 --> 02:10:44.119 connections by using an AC circuit tester. So make sure 1934 02:10:44.119 --> 02:10:49.479 you follow the right proper wiring sizes for the right conductors, 1935 02:10:49.800 --> 02:10:53.479 all right. Fuses and circuit breakers are used to interrupt 1936 02:10:53.560 --> 02:10:57.199 excessive current flow. Fuses do so by melting a short 1937 02:10:57.279 --> 02:11:00.760 length of metal. Circuit breakers act like a fuse, but 1938 02:11:00.960 --> 02:11:05.720 trip when current overloads occur. Always use properly sized fuses 1939 02:11:05.720 --> 02:11:08.920 and circuit breakers. When installing fuses or circuit breakers in 1940 02:11:08.960 --> 02:11:12.000 an AC circuit, be sure to replace them only with 1941 02:11:12.079 --> 02:11:15.920 the correct ones, never in the in the correct lines, 1942 02:11:16.039 --> 02:11:19.800 never in the neutral or ground lines. Be sure there's 1943 02:11:19.840 --> 02:11:22.479 a fuse or circuit breaker in the hot conductor for 1944 02:11:22.479 --> 02:11:25.359 one hundred and twenty bolt circuits and both conductors for 1945 02:11:25.439 --> 02:11:30.600 two hundred and forty bolt circuit round fault interrupted circuit 1946 02:11:30.600 --> 02:11:33.520 breakers are used in AC power circuits to prevent electrical 1947 02:11:33.560 --> 02:11:39.000 shock trips. It trips if unbalanced is since in currents 1948 02:11:39.039 --> 02:11:42.960 carried by the hot and neutral conductors. Sensitivity is just 1949 02:11:43.000 --> 02:11:45.960 a few million amps of a balance between the hot 1950 02:11:45.960 --> 02:11:53.239 and neutral, well below the threshold for electrical injury safety interlocks. 1951 02:11:53.279 --> 02:11:56.600 This is a switch that prevents dangerous voltages or intense 1952 02:11:56.760 --> 02:11:59.920 RF from being present when a cabinet or enclosure is open. 1953 02:12:01.680 --> 02:12:03.159 You'll see these a lot if you have a high 1954 02:12:03.199 --> 02:12:06.359 power amplifier, especially two amplifiers. When you take the top off, 1955 02:12:06.399 --> 02:12:10.439 there's usually a switch that disables all the voltages. So 1956 02:12:10.960 --> 02:12:13.000 if you're working on it and you know if you've 1957 02:12:13.039 --> 02:12:15.960 got to bypass that, be real careful, all right. Several 1958 02:12:15.960 --> 02:12:19.920 types physically disconnect high voltage RF when activated. Those are 1959 02:12:19.960 --> 02:12:22.880 the switches I was just talking about. Usually take the 1960 02:12:23.000 --> 02:12:26.800 chassis apart. There's usually a little rocker switch or some 1961 02:12:26.880 --> 02:12:30.640 kind of switch in there that senses that shorts or 1962 02:12:30.680 --> 02:12:34.439 ground high bolted circuits when activated, possibly blowing a circuit 1963 02:12:34.439 --> 02:12:38.800 breaker or fuse, and the power supplies. Which wire wires 1964 02:12:38.840 --> 02:12:41.600 in a four conductor to forty vowl AC circuit should 1965 02:12:41.600 --> 02:12:46.880 be attached to fuses or circuit breakers? Okay, only the 1966 02:12:46.880 --> 02:12:50.600 hot wires A you should not fuse The ground or 1967 02:12:50.800 --> 02:12:55.159 circuit should not fuse The ground wires according to the 1968 02:12:55.239 --> 02:12:58.239 Natural Electric Safety Code. What is the minimum wire size 1969 02:12:58.239 --> 02:13:01.319 that may be used safely for it twenty amp circuit? 1970 02:13:02.079 --> 02:13:06.239 That would be the twelve gate wire. What size a 1971 02:13:06.319 --> 02:13:09.079 fuse or circuit breaker would be appropriate to use a 1972 02:13:09.159 --> 02:13:12.359 circuit that uses a twenty A fourteen gauge wire. That 1973 02:13:12.399 --> 02:13:16.960 would be the fifteen amp circuit breaker. Which of the 1974 02:13:16.960 --> 02:13:20.079 following conditions may cause a ground false circuit interrupted? To 1975 02:13:20.079 --> 02:13:23.640 disconnect AC power current flowing and one or more of 1976 02:13:23.680 --> 02:13:27.159 the hot wires and the neutral or the hot wires 1977 02:13:27.199 --> 02:13:30.239 to ground over voltage of the wires. It would be 1978 02:13:30.439 --> 02:13:32.840 current flowing from one or more of the hot wires 1979 02:13:32.880 --> 02:13:37.079 directly to the ground. B Which of the following is 1980 02:13:37.079 --> 02:13:40.760 covered by the National Electric Code? That would be the 1981 02:13:40.760 --> 02:13:45.119 electrical safety of the station. What is the purpose of 1982 02:13:45.159 --> 02:13:49.760 a power supply interlock? Let's see it would be to 1983 02:13:49.880 --> 02:13:52.439 ensure dangerous voltage or mirder moved from the cabinet when 1984 02:13:52.439 --> 02:13:56.439 it's opened. That would be c okay. Some generals, some 1985 02:13:57.000 --> 02:14:02.680 generator safety, fueling and ventilation problems cause more injuries associated 1986 02:14:02.680 --> 02:14:10.079 with generators than from any other cause. Install generators outdoors, 1987 02:14:10.640 --> 02:14:13.720 use them outdoors, Carbon monoxide and exhaust and quickly build 1988 02:14:13.800 --> 02:14:18.479 up to toxic levels. We're using generators regularly. Installs carbon 1989 02:14:18.520 --> 02:14:23.439 diox carbon monoxide detector alarms in living and working areas. 1990 02:14:24.359 --> 02:14:27.399 Generator output connected directly to the homes. Wiring system must 1991 02:14:27.479 --> 02:14:30.680 have the ability to disconnect power service from utility lines. 1992 02:14:32.199 --> 02:14:35.039 Generators should always be shut off when refueling to avoid 1993 02:14:35.079 --> 02:14:39.279 igniting fumes or splashing liquids from the spark flobe. A 1994 02:14:39.359 --> 02:14:42.079 fire extinguishers should be kept near the generator and separated 1995 02:14:42.159 --> 02:14:46.279 from the fuel. Here's some practice questions. Which of the 1996 02:14:46.319 --> 02:14:51.279 following is true of an emergency generator installation. Generator should 1997 02:14:51.279 --> 02:14:54.039 be operating, well operated and it's insulated from ground. It 1998 02:14:54.079 --> 02:14:57.079 would be a should be operated in a well ventilated area. 1999 02:14:58.600 --> 02:15:07.079 Lighting lightning goals of lightning protection. You should provide fire 2000 02:15:07.119 --> 02:15:11.960 prevention for your home. It should it reduces or prevents 2001 02:15:12.000 --> 02:15:16.960 electrical damage to your equipment. Use metal heavy use metal 2002 02:15:17.279 --> 02:15:22.199 entry panels where signal control cables entered the house. Panels 2003 02:15:22.199 --> 02:15:25.920 should be grounded nearby with a heavy metal strap. Ground 2004 02:15:26.000 --> 02:15:28.920 rod must be bonded to the AC service entry ground 2005 02:15:29.000 --> 02:15:32.159 rod outside the building with the heavy conductor and lightning 2006 02:15:32.239 --> 02:15:34.760 arrestors should be installed at the entry panel where the 2007 02:15:34.800 --> 02:15:39.119 feed line enters grounding wires and straps should be as 2008 02:15:39.119 --> 02:15:42.279 short and directly and direct as possible. Do not use 2009 02:15:42.319 --> 02:15:47.760 solder or to make ground connect ground connections. Solder joints 2010 02:15:48.600 --> 02:15:52.880 could melt if hit by lightning size current. Use medical clamps, 2011 02:15:52.960 --> 02:15:57.199 braising or whaling so you know. Never use a solder 2012 02:15:57.279 --> 02:16:01.920 connection for your Whever you use solder to make ground connections, 2013 02:16:01.960 --> 02:16:05.640 where you can have lightning compete, All towers, mass and 2014 02:16:05.680 --> 02:16:11.199 antennas should be grounded. What should Why should solder joints 2015 02:16:11.239 --> 02:16:15.079 not be used in lightning protections because a solder lightning 2016 02:16:15.079 --> 02:16:17.399 will likely be destroyed by the heat of lightning. A. 2017 02:16:19.399 --> 02:16:24.119 Where should the station's lighting lightning protection ground system be located? 2018 02:16:25.159 --> 02:16:30.159 It should be outside the building of force. Which of 2019 02:16:30.159 --> 02:16:35.479 the following is required for lightning protection? Ground rods lightning 2020 02:16:35.559 --> 02:16:38.440 al must be connected d They all must be bombed 2021 02:16:38.440 --> 02:16:44.280 together with all other grounds. Where should lightning arrestors be located? 2022 02:16:45.319 --> 02:16:53.000 Where where it enters the building? They are exposure at 2023 02:16:53.040 --> 02:16:55.920 high power levels. For some frequencies, the amount of energy 2024 02:16:55.959 --> 02:16:59.000 that the body absorbs can be a problem. The maximum 2025 02:16:59.000 --> 02:17:04.840 permissible expose your MPE is maximum intensity is the maximum 2026 02:17:04.840 --> 02:17:07.719 intensity of r radiation to which a human being can 2027 02:17:07.760 --> 02:17:13.040 be maybe exposed. Factor to consider when estimating MPE, that is, 2028 02:17:13.120 --> 02:17:18.600 transmitter power level, density, frequency, average exposure time, and duty 2029 02:17:18.680 --> 02:17:22.680 cycle of the transmission. Power density and frequency are primary ones. 2030 02:17:22.879 --> 02:17:25.959 Those are things that you should think about. How much 2031 02:17:26.079 --> 02:17:30.520 power you putting out? What's your frequency? What's your exposure time? 2032 02:17:30.520 --> 02:17:35.559 In the duty sizet. Stations with a time average transmission 2033 02:17:35.600 --> 02:17:37.520 of more than one milli a lot are subject to 2034 02:17:37.520 --> 02:17:41.440 the FCC's ARF exposure rules. If your station exceeds the 2035 02:17:41.479 --> 02:17:44.559 exemption criteria, you will need to evaluate it and according 2036 02:17:44.600 --> 02:17:48.440 to the FCC OEt bulletin sixty five, So what does 2037 02:17:48.479 --> 02:17:53.159 that mean? So talk about that in a minute. Power 2038 02:17:53.239 --> 02:17:56.840 density is heating from exposure to RF signals caused by 2039 02:17:56.879 --> 02:18:00.520 the body tissue absorption of r F energy, measured in 2040 02:18:00.639 --> 02:18:04.799 milliwats per centimeter squared. R F field strings can also 2041 02:18:04.840 --> 02:18:07.399 be measured in volts per meter and amps frem or 2042 02:18:07.440 --> 02:18:12.319 milliwatts centimeter squared is the most useful for amateur requirements. 2043 02:18:12.680 --> 02:18:15.239 Power density is highest near antennas and in the directions 2044 02:18:15.239 --> 02:18:18.840 of which antennas have the highest gain, decreasing transmitter to 2045 02:18:18.840 --> 02:18:22.399 power and increasing distance from the antenna lowers power density 2046 02:18:23.040 --> 02:18:28.840 and vice versa absorption and limits SAR, which is specific 2047 02:18:28.920 --> 02:18:31.959 absorption rate. This is the rate at which energy is 2048 02:18:32.000 --> 02:18:36.399 absorbed from the is energy absorbed from the power to 2049 02:18:36.440 --> 02:18:40.879 which the body is is exposed. It's best the best 2050 02:18:40.920 --> 02:18:47.200 measure of ARF exposure, but it's difficult to measure. SAR 2051 02:18:47.559 --> 02:18:51.639 varies with the frequency, power density, average amount of exposure, 2052 02:18:51.639 --> 02:18:56.120 and duty of cycle of transmission. SAR depends on frequency 2053 02:18:56.239 --> 02:18:59.399 and size of the body or body part affected. Highest 2054 02:18:59.520 --> 02:19:03.399 where the body or body parts are naturally resonant. Safe 2055 02:19:03.479 --> 02:19:06.760 levels of STAR based on are based on demonstrated hazards 2056 02:19:06.760 --> 02:19:09.040 have been established by the FCC in the form of 2057 02:19:09.079 --> 02:19:15.799 maximum permissible exposure limits or the MPE levels. Maximum permissible 2058 02:19:15.840 --> 02:19:20.319 exposure MP limits vary with frequency because the body responds 2059 02:19:20.360 --> 02:19:24.600 differently to energy at different frequencies. The controlled and uncontrolled 2060 02:19:24.600 --> 02:19:28.000 limits refer to the environment in which people are exposed 2061 02:19:28.040 --> 02:19:31.200 to the r F energy be taken into account the 2062 02:19:31.280 --> 02:19:33.799 variation of the body sensitivities to r F energy at 2063 02:19:33.799 --> 02:19:38.799 different frequencies. So you can see here that based on 2064 02:19:38.879 --> 02:19:42.920 the frequency, the power density levels in a controlled and 2065 02:19:43.040 --> 02:19:49.239 uncontrolled environment UH at different frequencies. So in this particular case, 2066 02:19:49.360 --> 02:19:53.200 the this is where the body is more most sensitive 2067 02:19:53.360 --> 02:20:00.440 to RF radiation mm HM. The limits of occupational controlled 2068 02:20:00.440 --> 02:20:03.520 exposure UH. These are the you've got frequency range, the 2069 02:20:03.559 --> 02:20:08.479 power density UH controlled environment in the in the uncontrolled 2070 02:20:08.520 --> 02:20:15.760 environment ranges, controlled exposures limits supplies to control. The controlled 2071 02:20:15.760 --> 02:20:19.479 exposure limits apply to individuals trained in r F exposures, 2072 02:20:19.479 --> 02:20:24.399 such as the licensed amateurs. Uncontrolled environment is is those 2073 02:20:24.440 --> 02:20:27.719 who is the general publics and their levels are just 2074 02:20:27.760 --> 02:20:30.920 a different level, are just a different are are just 2075 02:20:30.959 --> 02:20:34.399 a little higher. UH. The uncontrolled exposure limits apply to 2076 02:20:34.440 --> 02:20:37.639 individuals not trained in r F exposure, so the general 2077 02:20:37.680 --> 02:20:42.639 public UH. And you'll notice here. So so these are 2078 02:20:42.680 --> 02:20:45.879 the frequency ranges and their exposure levels and the average 2079 02:20:45.920 --> 02:20:52.479 time you you're required as an UH, you're required to 2080 02:20:52.520 --> 02:20:57.000 do a UH UH an exposure analysis for your station. 2081 02:20:58.639 --> 02:21:00.760 There's an r F calculator at the A at the 2082 02:21:00.760 --> 02:21:02.760 a dobr L that allows you to put in some 2083 02:21:02.799 --> 02:21:10.559 of these things here, such as such as UH transmitting frequency, 2084 02:21:11.200 --> 02:21:14.920 antenna gain, and it will calculate the safe distance based 2085 02:21:14.920 --> 02:21:19.120 on the exposure levels that you need to maintain. Okay, 2086 02:21:21.120 --> 02:21:23.959 the things that control the duty, the things that are 2087 02:21:24.200 --> 02:21:27.159 The things that control duty cycle UH and the uncontrolled 2088 02:21:27.239 --> 02:21:31.440 environment are exposure RF energy, which is average over fixed 2089 02:21:31.520 --> 02:21:36.479 time intervals. Time averaging evaluates a total RF exposure over 2090 02:21:36.520 --> 02:21:40.959 a fixed time in two types of averaging periods are 2091 02:21:41.120 --> 02:21:44.479 controlled and uncontrolled. The controlled is where you're aware of 2092 02:21:44.520 --> 02:21:47.000 your exposure and are expected to take reasonable steps to 2093 02:21:47.040 --> 02:21:53.040 minimize in controlled environment examples transmitting the controlled environment examples 2094 02:21:53.399 --> 02:21:58.000 transmitting facilities near antennas. Uncontrolled environments are like general public 2095 02:21:58.040 --> 02:22:01.959 asset our general public access. People in an uncontrolled environment 2096 02:22:02.040 --> 02:22:04.639 are not aware of their exposure but are much likely 2097 02:22:04.680 --> 02:22:12.319 to receive continuous exposure. Sure duty cycle is a ratio 2098 02:22:12.360 --> 02:22:14.280 of the time the transmitter is on to the total 2099 02:22:14.319 --> 02:22:18.399 time during the exposure. Maximum is one hundred percent, same 2100 02:22:18.399 --> 02:22:21.319 as duty factor, but duty factor is expressed as a fraction. 2101 02:22:23.479 --> 02:22:27.399 A lower transmission duty cycle permits greater short term exposure 2102 02:22:27.840 --> 02:22:31.840 levels for a given average exposure. The less time the 2103 02:22:31.879 --> 02:22:35.840 transmitter is on, the lower the average exposure, permitting greater 2104 02:22:36.079 --> 02:22:40.760 short term exposure levels for a given average exposure. Along 2105 02:22:41.280 --> 02:22:45.000 with operational duty cycle, the different modes themselves have different 2106 02:22:45.040 --> 02:22:51.879 emission duty cycles. Operating duty factors of modes commonly used 2107 02:22:52.799 --> 02:22:57.040 by amateurs. For most amateurs, operating listening and transmitting time 2108 02:22:57.079 --> 02:23:00.239 are about the same, So duty cycle is rare really 2109 02:23:00.399 --> 02:23:09.879 higher than fifty percent. Right. Calculating the average duty cycle 2110 02:23:09.920 --> 02:23:13.280 power a station is using single side band without speech processing, 2111 02:23:13.719 --> 02:23:17.840 transmitting listening for equal amounts of time and with transmitted 2112 02:23:17.879 --> 02:23:20.520 power one hundred and fifty watch calculating the average outfoot power. 2113 02:23:20.959 --> 02:23:24.319 Average duties power cycle is equal to the transmitted power 2114 02:23:24.920 --> 02:23:28.959 times the emission duty cycle times of operating duty cycle. 2115 02:23:29.719 --> 02:23:31.600 So if you've got a transmitting power of one hundred 2116 02:23:31.600 --> 02:23:38.319 and fifty wats and uh, and you've got a duty 2117 02:23:38.319 --> 02:23:43.200 cycle for about twenty percent processing operating fifty percent of 2118 02:23:43.200 --> 02:23:45.239 the time, then your average duty cycle power to be 2119 02:23:45.239 --> 02:23:47.959 one hundred and fifty wats times twenty times fifty percent 2120 02:23:48.200 --> 02:23:58.639 about fifteen watts. Let's see's back up at a section 2121 02:23:58.680 --> 02:24:02.479 again here. Yeah, guys are talking. I know you guys 2122 02:24:02.520 --> 02:24:05.840 are talking, but it's kind of affected me a little bit. No, no, no, 2123 02:24:05.879 --> 02:24:08.239 it's okay. I just want to just redo a section 2124 02:24:09.760 --> 02:24:17.120 talking about we're going to go back to uh figure 2125 02:24:17.479 --> 02:24:21.120 I mean, I mean you guys. Uh. Let's go back 2126 02:24:21.239 --> 02:24:28.520 starting with RF exposure section nine point two slide thirty two. Okay, okay, 2127 02:24:28.600 --> 02:24:30.600 so I'm going to start here and you got I know, 2128 02:24:30.680 --> 02:24:32.479 you got to talk, but if it's sort of contract 2129 02:24:32.520 --> 02:24:36.799 me a little bit. And I was okay, yeah, yeah, 2130 02:24:36.840 --> 02:24:38.680 I just figured let me go back and do that 2131 02:24:38.719 --> 02:24:41.440 section again. Okay, is this the last section? Yeah, this 2132 02:24:41.520 --> 02:24:43.959 is the last thing. We're thirty two sixty four at 2133 02:24:44.000 --> 02:24:47.239 thirty two slides left and we're done. Ok But I 2134 02:24:47.360 --> 02:24:50.840 was more reading. I was getting a little it didn't 2135 02:24:50.840 --> 02:24:54.040 sound too good what I was doing. So yeah, well 2136 02:24:54.120 --> 02:24:56.120 that's up. Let me look at this see if you 2137 02:24:56.200 --> 02:25:02.680 got enough, if you got enough time, find you got 2138 02:25:02.760 --> 02:25:05.840 thirty six minutes levels. Okay, I think I can do that. Yeah, 2139 02:25:06.440 --> 02:25:09.479 so you all be on the same file. Yeah, okay, 2140 02:25:10.000 --> 02:25:14.719 so we're going to start RF exposure again. Okay, okay, 2141 02:25:16.079 --> 02:25:18.760 so you can find this chart and sorry about that. 2142 02:25:19.159 --> 02:25:22.440 I just want to make sure I just sounded pretty good. Okay, 2143 02:25:22.559 --> 02:25:26.520 we're going to talk about our exposure. This has to 2144 02:25:26.559 --> 02:25:29.479 do at at high power levels. For some frequencies, the 2145 02:25:29.479 --> 02:25:33.879 amount of energy that the body absorbs can be a problem. Uh, 2146 02:25:34.479 --> 02:25:38.280 there's a maximum permissible exposure called MPE, and that's the 2147 02:25:38.319 --> 02:25:40.840 maximum intensity of r IF radiation to which a human 2148 02:25:40.879 --> 02:25:45.440 being can be exposed. Factors to consider when calculating your 2149 02:25:45.520 --> 02:25:51.920 MPE are transmit power level or density, the frequency, the 2150 02:25:52.000 --> 02:25:55.719 average exposure time, and the duty cycle of the transmission, 2151 02:25:55.840 --> 02:25:59.040 which is power density and frequency are the primary ones here. 2152 02:25:59.760 --> 02:26:02.520 Stations with a time average transmission of more than one 2153 02:26:02.559 --> 02:26:05.760 milliwat are subject to the FCC's r IF exposure rules. 2154 02:26:06.079 --> 02:26:08.879 If your station exceeded the exemption criteria, you will need 2155 02:26:08.920 --> 02:26:11.959 to evaluate it according to the FCC, and it has 2156 02:26:11.959 --> 02:26:16.159 an OEt bullet in sixty five. The ABRIL has a 2157 02:26:16.239 --> 02:26:20.000 online calculator where you can go calculate what the RF 2158 02:26:20.040 --> 02:26:23.920 exposure is or how what's the minimum distance someone needs 2159 02:26:23.920 --> 02:26:27.959 to be from your transmitting and transmitting antennum. And we're 2160 02:26:27.959 --> 02:26:31.000 going to talk about there's two environments. We'll talk about 2161 02:26:31.040 --> 02:26:35.760 power density first. U power density is heating from exposure 2162 02:26:35.840 --> 02:26:39.680 to RF signals is caused by the body tissues absorbing 2163 02:26:39.799 --> 02:26:43.200 r F energy. It's measured in wats per milliwats per 2164 02:26:43.239 --> 02:26:47.239 centimeter square. R F field strengths can also be measured 2165 02:26:47.280 --> 02:26:50.479 in volt super meter or amps per meter, but milli 2166 02:26:50.559 --> 02:26:53.000 wats per meter centimeter squared is the most useful for 2167 02:26:53.040 --> 02:26:58.639 amateur requirements. The power density is highest near your transmitting 2168 02:26:58.680 --> 02:27:01.559 antennas and the directions of which the antennants have the 2169 02:27:01.639 --> 02:27:06.840 most gained. Decreasing the transmitting power that the transmitter power 2170 02:27:07.079 --> 02:27:09.879 and increasing the distance from the antenna will lower the 2171 02:27:10.239 --> 02:27:16.840 power density, and vice and vice versa. The absorption in limits, 2172 02:27:16.920 --> 02:27:20.840 there's a unit called SAR, which is a specific absorption rate. 2173 02:27:21.479 --> 02:27:23.719 Is the rate at which energy is absorbed from the 2174 02:27:23.799 --> 02:27:27.600 power from from power to which the body is exposed. 2175 02:27:29.879 --> 02:27:32.399 It's it's the best to measure you are if exposure, 2176 02:27:33.040 --> 02:27:35.680 but it's sometimes it's best to measure, but sometimes it's 2177 02:27:35.719 --> 02:27:37.920 difficult to go back to actually do it. And it 2178 02:27:38.079 --> 02:27:41.879 varies from with frequency, power density, average amount of exposure, 2179 02:27:41.920 --> 02:27:44.680 and duty cycle. All those are factors that come into 2180 02:27:44.840 --> 02:27:48.760 the SAR. The SAR measurement and also depends on the 2181 02:27:48.840 --> 02:27:51.719 frequency and size of the body and the body part affected. 2182 02:27:52.280 --> 02:27:54.920 UH It's it's highest where the body and the body 2183 02:27:54.959 --> 02:27:59.040 parts are naturally resonant. Safe levels of SAR are based 2184 02:27:59.079 --> 02:28:01.959 on demonstrated hazards and have been established by the FCC 2185 02:28:02.120 --> 02:28:05.680 in the form of maximum permissional exposure limits. So they've 2186 02:28:05.760 --> 02:28:07.520 taken all this to effect and they've come up with 2187 02:28:07.680 --> 02:28:12.600 the thing called the mp ees. M p E is 2188 02:28:12.719 --> 02:28:17.360 the maximum PERMISSIONBLE exposure. And these limits vary with frequency 2189 02:28:17.600 --> 02:28:21.799 and UH. And they've they've come out and characterized the 2190 02:28:22.799 --> 02:28:27.399 the the MPE based on frequency and power densities. And 2191 02:28:27.479 --> 02:28:30.079 this chart here shows that. And there's two levels. There's 2192 02:28:30.079 --> 02:28:34.120 a controlled environment in an uncontrolled environment. The controlled environment 2193 02:28:34.280 --> 02:28:39.879 is where UH. The controlled environment is is is where 2194 02:28:40.360 --> 02:28:43.159 the people are are aware of the are aware of 2195 02:28:43.360 --> 02:28:49.200 r F and UH usually controlled by m can be 2196 02:28:49.319 --> 02:28:56.559 controlled by UH access. Let's see, I'm gonna do this 2197 02:28:56.680 --> 02:29:00.600 chart again. Okay, we're doing yeah, you and milling them 2198 02:29:00.639 --> 02:29:05.200 with respact to get up, doctor. That's okay, okay. Maximum 2199 02:29:05.280 --> 02:29:09.040 permissible exposure or MP limits vary with frequency because the 2200 02:29:09.079 --> 02:29:12.520 body responds differently to energy at different at different frequencies. 2201 02:29:12.760 --> 02:29:16.200 The controlled and uncontrolled limits refer to the environment in 2202 02:29:16.239 --> 02:29:19.440 which people are exposed to the r IF energy. These 2203 02:29:19.520 --> 02:29:22.600 take into account the variations in the body's sensitivity to 2204 02:29:22.760 --> 02:29:28.879 r F energy at different frequencies. The limits for occupation 2205 02:29:29.200 --> 02:29:32.799 and controlled exposure are shown here. The controlled exposure limits 2206 02:29:32.840 --> 02:29:37.200 apply to individuals trained in RF exposure, such as licensed amateurs. 2207 02:29:38.959 --> 02:29:43.239 Uncontrolled exposure limits applied to individuals not trained in RF exposure, 2208 02:29:43.319 --> 02:29:51.239 so usually that's the general public. Okay. Exposure of r 2209 02:29:51.319 --> 02:29:55.000 F energy is averaged over fixed time intervals. Time averaging 2210 02:29:55.079 --> 02:29:58.639 evaluates that the total r F exposure over a fixed 2211 02:29:58.680 --> 02:30:02.559 time energy two types of averaging periods. There's the controlled 2212 02:30:02.680 --> 02:30:05.799 and the uncontrolled. And the controlled averaging you're aware of 2213 02:30:05.840 --> 02:30:08.360 your exposure and are expected to take reasonable steps to 2214 02:30:08.399 --> 02:30:14.879 minimize Controlled environment examples include transmitting facilities near antennas. An 2215 02:30:14.959 --> 02:30:18.959 uncontrolled environment would be like public access. People are in 2216 02:30:19.040 --> 02:30:21.600 an uncontrolled environment are not aware of their exposure, but 2217 02:30:21.719 --> 02:30:28.440 are much less likely to receive continuous exposure. Duty cycle 2218 02:30:28.639 --> 02:30:31.319 is the ratio of the time the transmitter is on 2219 02:30:32.000 --> 02:30:38.959 to the total time during exposure. Duty cycle is expressed 2220 02:30:39.000 --> 02:30:43.600 in a fraction instead of twenty five percent, So a 2221 02:30:43.719 --> 02:30:48.239 lower transmission duty cycle permits greater short term exposure levels 2222 02:30:48.280 --> 02:30:52.040 for a given average exposure. Called operational duty cycle, the 2223 02:30:52.159 --> 02:30:55.520 less time the transmitter is on, the lower the average exposure, 2224 02:30:56.239 --> 02:30:59.879 permitting greater short term exposure levels for a given average exposure. 2225 02:31:00.079 --> 02:31:04.600 So along with operational duty cycle, the different modes themselves 2226 02:31:04.680 --> 02:31:09.879 have different emission duty cycles. Twenty to forty percent duty 2227 02:31:09.959 --> 02:31:13.639 cycle if you're doing a single side van with AFSK 2228 02:31:13.879 --> 02:31:16.600 or slow scan TV, that's one hundred percent single side 2229 02:31:16.879 --> 02:31:21.920 excuse me, and voice amplitude like AM modulation is fifty 2230 02:31:21.959 --> 02:31:25.680 percent twenty one hundred percent. AM modulation is twenty five 2231 02:31:25.719 --> 02:31:29.520 percent duty cycle FM voice one hundred percent duty cycle 2232 02:31:29.600 --> 02:31:32.879 digital FM one hundred percent. So that all the digital 2233 02:31:33.000 --> 02:31:36.680 modes that we use that we talked about are one 2234 02:31:36.760 --> 02:31:40.920 hundred percent duty cycle modes like j like JTA. When 2235 02:31:40.920 --> 02:31:43.319 your transmitters on is we consider it's one hundred percent 2236 02:31:43.399 --> 02:31:50.360 duty cycle. Okay. Calculating the average duty cycle a station. 2237 02:31:51.159 --> 02:31:54.120 If a station is using single side van without speech processing, 2238 02:31:54.760 --> 02:31:57.520 transmitting and listening for equal amounts of time, and when 2239 02:31:57.559 --> 02:32:00.319 transmitting power of one hundred and fifty watts, how how 2240 02:32:00.319 --> 02:32:04.040 would we calculate that average power output? So the average 2241 02:32:04.280 --> 02:32:08.120 duty cycle power is the transmitted power times the emission 2242 02:32:08.200 --> 02:32:11.040 duty cycle at times of operating duty cycle. So in 2243 02:32:11.120 --> 02:32:14.799 this particular case, we've got one hundred and fifty watts, 2244 02:32:15.159 --> 02:32:17.760 where we've got an emission duty cycle for single sideband 2245 02:32:17.799 --> 02:32:21.159 about twenty percent, and are operating duty cycle is fifty percent, 2246 02:32:21.799 --> 02:32:24.200 So our average duty cycle power I got one hundred 2247 02:32:24.200 --> 02:32:27.600 and fifty watts, but on times twenty percent of my 2248 02:32:27.760 --> 02:32:31.200 mission duty cycle times transmitting fifty percent of the time, 2249 02:32:31.280 --> 02:32:35.719 I get fifteen watts if you want to. If you 2250 02:32:36.479 --> 02:32:40.520 all fixed ameateur stations must evaluate their capability to cause 2251 02:32:40.639 --> 02:32:43.079 RF exposure no matter whether they are using high or 2252 02:32:43.200 --> 02:32:49.440 low power. Limits vary with frequency and PEP. You're required 2253 02:32:49.440 --> 02:32:52.000 to perform the evaluation that your power exceeds the level 2254 02:32:52.079 --> 02:32:57.360 shown for any band. The r IF exposure evaluation is 2255 02:32:57.399 --> 02:33:01.200 limited by three different methods during r F field strength 2256 02:33:01.319 --> 02:33:05.959 with calibrated meters UH using the computer or model calculating 2257 02:33:06.719 --> 02:33:10.360 to calculate your exposure or the easiest way is to 2258 02:33:10.479 --> 02:33:12.920 use the a double r l's online calculator for r 2259 02:33:13.079 --> 02:33:17.520 F exposure. So what you need to do to use 2260 02:33:17.559 --> 02:33:20.520 the exposure calculator is what's the power of your antenna 2261 02:33:21.479 --> 02:33:25.360 including adjustments for feed for for a duty cycle and 2262 02:33:25.440 --> 02:33:28.600 feed line loss. UH. You got to know your antenna gain, 2263 02:33:28.680 --> 02:33:31.719 your high above ground, and you're operating frequency. And when 2264 02:33:31.719 --> 02:33:36.200 you have those items, UH, you can go use the 2265 02:33:36.559 --> 02:33:41.159 exposure calculator to figure out, UH what the exposure is 2266 02:33:41.200 --> 02:33:46.280 around your antenna system. When when when you UH, what 2267 02:33:46.520 --> 02:33:49.040 what I've done for my home is I've got I 2268 02:33:49.120 --> 02:33:51.600 know what antennas I have, I know what operating modes 2269 02:33:51.639 --> 02:33:54.360 I use, and I go run that calculation through that 2270 02:33:54.600 --> 02:33:56.840 a double r L calculator. I print those out and 2271 02:33:56.959 --> 02:33:59.840 I've got those at my station, so I know uh 2272 02:34:00.280 --> 02:34:05.959 how far or how close uh people can can can 2273 02:34:06.079 --> 02:34:09.959 be to my systems. And for my home use, I'm 2274 02:34:10.000 --> 02:34:14.520 in pretty good shape. I've got an unfenced backyard. But 2275 02:34:15.159 --> 02:34:18.879 at the my my worst case is like ten feet 2276 02:34:18.959 --> 02:34:21.319 from the end from from the end from the antenna, 2277 02:34:21.520 --> 02:34:23.719 and all my intentors are ten feet above the ground. 2278 02:34:23.760 --> 02:34:27.920 So my my RF exposure analysis shows on them in 2279 02:34:27.959 --> 02:34:31.200 pretty good shape. Whenever I go to a public service event, 2280 02:34:33.159 --> 02:34:36.280 if we're out in the public like a field day, 2281 02:34:37.239 --> 02:34:40.000 you should go to an exposure analysis of the antenna's 2282 02:34:40.000 --> 02:34:41.479 that you're going to be used. And you should. And 2283 02:34:41.600 --> 02:34:45.440 if you've gotten an area where the public can get 2284 02:34:45.479 --> 02:34:47.239 close to antennas, then you're gonna have to use some 2285 02:34:47.360 --> 02:34:51.079 barriers to market offer to keep people away. Okay, so 2286 02:34:51.239 --> 02:34:54.360 here's some good practices for RF exposure. You know, locate 2287 02:34:54.440 --> 02:34:56.879 and move antennas away from where people can be exposed 2288 02:34:57.280 --> 02:35:00.200 to excessive r F fields. Locate the antenna's a away 2289 02:35:00.200 --> 02:35:03.680 from property lines and place fencils around the base of 2290 02:35:03.760 --> 02:35:08.280 the ground mounted antennas. Don't point gain antennas where people 2291 02:35:08.280 --> 02:35:11.559 are likely to be. Use beam antennas to direct RF 2292 02:35:11.680 --> 02:35:15.479 energy away from the people. When using stealth, addict or 2293 02:35:15.520 --> 02:35:18.280 indoor antennas. Make sure your MP limits are not exceeded 2294 02:35:18.319 --> 02:35:22.719 in your living quarters. VHF and UHF. Place mobile antennas 2295 02:35:22.760 --> 02:35:24.799 on a roof or trunk of a car to maximize 2296 02:35:24.799 --> 02:35:29.000 shielding of fasseters. Use dummy load or dummy antennas when 2297 02:35:29.040 --> 02:35:33.000 testing a transmitter, and of course, reduce the power and 2298 02:35:33.079 --> 02:35:37.399 duty cycle of your transmissions. Yeah, here's some questions. What's 2299 02:35:37.479 --> 02:35:40.280 one of the ways that RF exposure can affect human 2300 02:35:40.319 --> 02:35:44.360 body tissues? It can heat up the body tissue. That's 2301 02:35:44.399 --> 02:35:46.440 what ARF exposure do is you can feel it as heat. 2302 02:35:46.799 --> 02:35:50.319 You'll hear people talk about RF burns. Which of the 2303 02:35:50.399 --> 02:35:53.600 following is used to determine ARF exposure from a transmitting signal, 2304 02:35:54.680 --> 02:35:59.680 power density, duty cycle? All of these are correct. All 2305 02:35:59.760 --> 02:36:03.520 those affect how much your R exposure. How can you 2306 02:36:03.520 --> 02:36:07.719 determine that your station complies with FCC RF exposure regulations? 2307 02:36:08.680 --> 02:36:12.280 You can calculate it using the FCC OEt bulletin Computer 2308 02:36:12.360 --> 02:36:15.639 modeling using fill screen. All those are are ways in 2309 02:36:15.719 --> 02:36:20.520 which you can measure your compliance with RF exposure. What 2310 02:36:20.680 --> 02:36:25.799 does time averaging mean when evaluating RF radiation exposure? See 2311 02:36:25.840 --> 02:36:29.840 average amount of time powers applied by the transmitter average time. 2312 02:36:29.959 --> 02:36:32.719 It's a total time. It's a total RF exposure over 2313 02:36:32.799 --> 02:36:37.360 a certain period. It would be d What must you 2314 02:36:37.479 --> 02:36:40.000 do if an evaluation of your station shows that the 2315 02:36:40.120 --> 02:36:43.719 artific energy radiated by your station exceeds permissible limits for 2316 02:36:44.600 --> 02:36:50.159 possible human absorption, take action to prevent exposure to the fields? 2317 02:36:50.399 --> 02:36:55.520 Filing it impact FCC Secure written permissions. It would be 2318 02:36:56.719 --> 02:37:00.559 a take action to prevent human exposure in the excessive 2319 02:37:00.719 --> 02:37:03.680 r F fields. What must you do if your station 2320 02:37:03.879 --> 02:37:09.120 fails to meet the FCC RF exposure exemption criteria? All right, 2321 02:37:09.239 --> 02:37:11.879 so what must you do if your station fails to 2322 02:37:11.959 --> 02:37:15.920 meet the FCC RF exposure criteria? So what you want 2323 02:37:15.959 --> 02:37:19.000 to do is a perform an RF exposure evaluation according 2324 02:37:19.040 --> 02:37:23.399 to those bulletins. Okay, what is the effect of modulation 2325 02:37:23.760 --> 02:37:28.639 duty cycle on RF exposure? The higher the duty cycle 2326 02:37:28.799 --> 02:37:33.280 creates let's see, ye, the higher the duty cycle from 2327 02:37:33.319 --> 02:37:36.479 its greater power levels to be transmitted. That makes sense. 2328 02:37:36.639 --> 02:37:39.600 The more your transmitters on, the higher the RF exposure 2329 02:37:39.680 --> 02:37:42.680 will be. Which of the following steps must an amateur 2330 02:37:42.719 --> 02:37:47.719 operator take to ensure compliance with FCC regulations. Let's see 2331 02:37:47.840 --> 02:37:51.559 POST a copy performer. Yeah, it's going to be C performer. 2332 02:37:51.680 --> 02:37:55.680 Routine art exposure valuation to prevent access to any identified 2333 02:37:56.239 --> 02:38:00.000 high exposure areas. Okay? And what type of instrument can 2334 02:38:00.159 --> 02:38:03.680 be used to actually measure r F field strength? Let's 2335 02:38:03.719 --> 02:38:08.200 see BB a calibrated field strength leader with a calibrated antenna. 2336 02:38:09.360 --> 02:38:12.399 What should be done if evaluation shows that a neighbor 2337 02:38:12.559 --> 02:38:16.399 might experience more than the allowable RF limit exposure from 2338 02:38:16.399 --> 02:38:20.799 the main lobe of a directional antenna? You can change 2339 02:38:21.040 --> 02:38:24.239 the antenna height game use an antenna with the higher 2340 02:38:24.319 --> 02:38:27.760 front the bank. Take precaution to ensure b C. Take 2341 02:38:27.840 --> 02:38:30.159 precautions ensure that your antenna cannot be pomed in the 2342 02:38:30.200 --> 02:38:34.760 direction when they are present. Okay, what precaution should you 2343 02:38:34.840 --> 02:38:40.479 take if you install an outdoor transmitting antenna b C. 2344 02:38:40.760 --> 02:38:45.799 Make sure the MPE limits are not exceeded in occupied areas. Okay. 2345 02:38:45.840 --> 02:38:49.840 What stations are subject to FCC rules on RF exposure? 2346 02:38:51.200 --> 02:38:54.719 That would be d all stations with the time average 2347 02:38:54.719 --> 02:38:59.319 transmission of more than one mili a lot. Okay, talk 2348 02:38:59.319 --> 02:39:03.200 a little bit about it. Outdoor safety installing antennas, make 2349 02:39:03.239 --> 02:39:05.920 sure you place all antennas and feed lines well clear 2350 02:39:06.159 --> 02:39:10.280 of power lines. No part of an antenna system should 2351 02:39:10.319 --> 02:39:13.600 be closer than ten feet from power lines. When working 2352 02:39:13.719 --> 02:39:18.200 on roofs, trees, or towers, climbers, helpers should wear appropriate 2353 02:39:18.280 --> 02:39:21.000 protective gear at all times. Run through a safety check 2354 02:39:21.040 --> 02:39:25.159 list every time, turn off and unplugged all AC equipment, 2355 02:39:25.959 --> 02:39:30.159 locking circuits out and tagging them if possible. Transmitters should 2356 02:39:30.200 --> 02:39:32.399 be off and it's connected from feed lines to avoid 2357 02:39:32.479 --> 02:39:37.079 shock or excessive arf exposure. Belts and harnesses must be written, 2358 02:39:37.639 --> 02:39:40.520 must be within their service life and attically rated for 2359 02:39:40.600 --> 02:39:43.639 the weight. Of course, check check the weather report, and 2360 02:39:43.719 --> 02:39:47.559 of course take your time. Here's some practice questions. Which 2361 02:39:47.600 --> 02:39:50.239 of these choices should be observed when climbing a tower 2362 02:39:50.399 --> 02:39:54.719 using a safety harness. Confirm that the harness is ready 2363 02:39:54.760 --> 02:39:56.600 for the weight of the climber and that is within 2364 02:39:56.760 --> 02:40:01.680 its allowable service life. Be done Before climbing a tower 2365 02:40:01.719 --> 02:40:06.600 that supports electrically powered devices, You should be make sure 2366 02:40:06.799 --> 02:40:10.559 all circuits that supply powers to the tower are locked 2367 02:40:10.639 --> 02:40:12.760 and tagged out. Are locked out and tagged