Speaker 1: Okay, So our next section we're going to talk about
Speaker 1: basics of digital modes, packet receiving, transmitting, digital mode, digital operation,
Speaker 1: digital modes. It's gonna be a lot of fun, all right.
Speaker 1: So some of the basics of a digital mode where
Speaker 1: to find digital activity. So communications are digital modes if
Speaker 1: the information is exchanged as individual characters encoded as digital
Speaker 1: bits such as Morse code, radio, teletype PSK, thirty one
Speaker 1: ft eight D star, DMR, slow scan TV, those are
Speaker 1: all forms of digital modes. Digital modes are restricted to
Speaker 1: CW SLASH data segments and the HF bands. They're found
Speaker 1: near the top of the CW segment on twenty meters.
Speaker 1: Most PSK stations are near fourteen seventy r TTY, other
Speaker 1: modes between seventy and fourteen. Table coming up to show
Speaker 1: some of that. CW isn't formally restricted anywhere in the bands.
Speaker 1: It's a digital mode, but you can use it anywhere.
Speaker 1: They has special privileges. Data rates and bandwidths are specified
Speaker 1: by the FCC rules. Digital codes not specified by the
Speaker 1: FCC must be public. You can have an experimental mode,
Speaker 1: but it's got to be published. People have to know
Speaker 1: what it is. Radio teletype originally used mechanical teleprinters, but
Speaker 1: migrated as computer sound cards. Most people use a computer
Speaker 1: sound card to generate their digital tones in these days.
Speaker 1: PSK thirty one Real, Real Popular, it's a good Week.
Speaker 1: Signal mode uses load transmit, packet teletype over radio win
Speaker 1: more is Windows based messaging over radio win war All
Speaker 1: those are popular types of HF digital modes. And there's
Speaker 1: packet radio common on VHF U HF twelve and nine
Speaker 1: six hundred bought on those bands. Okay, so here's the bands,
Speaker 1: here's the frequency range or where you will find some
Speaker 1: of the digital stuff hanging out. Most people here to
Speaker 1: that's pretty people follow it pretty well. So here's some
Speaker 1: definitions you might want to know for digital stuff. Airlink
Speaker 1: that's the part of the comp system that involves radio
Speaker 1: transmission and reception of signals. I don't think I've ever
Speaker 1: used that much, but air that's an airlink. Bit is
Speaker 1: the fundamental unit of data, as zero or a one,
Speaker 1: representing all the part of a binary number. There's the
Speaker 1: bit rate. That's the number of digital bits per second
Speaker 1: sent from one system to another. Bod is a number
Speaker 1: of symbols per second, and Symbols can be ten bit
Speaker 1: or eight bit based on the protocol you're using, but
Speaker 1: it's symbols per second sent from one station to another.
Speaker 1: The duty cycle is the ratio of the time that
Speaker 1: the transmitter is on to the total time plus the
Speaker 1: off time. Protocol are the rules that control the method
Speaker 1: used to exchange data between systems, and the mode is
Speaker 1: the combination of a protocol with the modulation method. Digital
Speaker 1: modes are regulated as voice emissions by the FCC. Digital
Speaker 1: Voice modes and those include d STAR System, fusion AR
Speaker 1: Digital Voice System d DMR. FSK individual bits of data
Speaker 1: encoded as tones. FSK uses tones as data are transmitted.
Speaker 1: Different tone frequencies are used to represent the one or
Speaker 1: the zero. The frequencies in a two tone FSK system
Speaker 1: called mark in space, space represents a zero and mark
Speaker 1: represents a one. In direct FSK, the frequency of the
Speaker 1: transmitter's BFO is controlled by a digital data signal from
Speaker 1: the computer, So either can send two tones through the
Speaker 1: audio passband or you can actually change the carrier frequency
Speaker 1: the same thing. It's a frequency shift. It's the same
Speaker 1: result audio frequency shift K, which is probably ninety eight
Speaker 1: percent of what we do in the hand radio is
Speaker 1: use audio tones modulated on single sideband or FTEM through
Speaker 1: the microphone input generated by a sound card. Typically, multiple
Speaker 1: FSK uses more than two tones and are used to
Speaker 1: create more codes. Most common type of the fs the
Speaker 1: PSK the face shift king. Most common type of face
Speaker 1: shift is to invert one of the tone waveforms by
Speaker 1: shifting at one hundred and eighty degrees. Rapid changers and
Speaker 1: face can be heard from from the human ear as
Speaker 1: a rasp, noise or buzz. The signature of a PSK
Speaker 1: sitting on the air received by by CW or CW
Speaker 1: single sideband receivers sort of sound like an old computer mode.
Speaker 1: Let's let's talk about some questions here in what segment
Speaker 1: of the twenty meter band are most digital modes operations
Speaker 1: commonly found. It's around between fourteen seventy and four D.
Speaker 1: What is a direct binary FSK modulated signal direct? Now
Speaker 1: we're doing direct, so you want to key the oscillator
Speaker 1: directly with their digital signal? Must be v okay. How
Speaker 1: are the two separate frequencies of a frequency shift key
Speaker 1: signal identified? Usually do marking space? Which of the following
Speaker 1: provided digit number of digital voice modes Okay, remember digital
Speaker 1: voice modes DMR D Star infusion. Those are digital voice modes.
Speaker 1: All these other ones have non voice modes. Okay, talk
Speaker 1: about some character based modes. Simplest use of digital communications
Speaker 1: as mode in which individual characters entered by an operator
Speaker 1: and transmitted to another station and they appear on another
Speaker 1: by another read by another operator, such as Morse code. Uh.
Speaker 1: Speeds are low but convenient to use and require a
Speaker 1: little additional equipment than a sound card or modem. So
Speaker 1: a lot of times it's a keyboard to keyboard. I
Speaker 1: typed the letter A, I transmitted it, and receive station
Speaker 1: gets it puts on his computer A. So we just
Speaker 1: did some character based transmission, sometimes referred to as keyboard
Speaker 1: to keyboard or chat. You transmit a stream of characters
Speaker 1: without additional data. That's referred to as unstructured. Oldest form
Speaker 1: of hand radio digital communication is r tt Yuh. This
Speaker 1: you sends the This is called BOTTO. It's a timing
Speaker 1: sequence for the bit pattern. Uh. Here we're trying to
Speaker 1: send the letter DS and dog. It starts a bit
Speaker 1: is set. You have some bits that tell it when
Speaker 1: it's starting. Then the data comes across and then you
Speaker 1: get a stop bit and you're done, and how fast
Speaker 1: it goes out is a bawd raad okay. R t
Speaker 1: t Y uses the BODO code, which is which represents
Speaker 1: each character has a five bit sequence. Five bit allows
Speaker 1: for thirty two different characters. That's not enough for their
Speaker 1: attire English language, you know, numerals and punctuation. There's two
Speaker 1: special flags, letters and figs that are used to switch
Speaker 1: between the two characters sets, and that doubles the amount
Speaker 1: of characters that can be sent. So there's a special
Speaker 1: character as a guy sending letters or numbers or something.
Speaker 1: You can set it and you get you know, you
Speaker 1: don't increase your your your five bits don't have to
Speaker 1: get bigger. Difference between mark and space tones is called
Speaker 1: the signal shift rtt Y. Usually that's at one hundred
Speaker 1: and seventy hertz. It's most common. It's not a rule,
Speaker 1: but that's what just better Buy uses. PSK thirty one
Speaker 1: is another mode. It's probably the most popular face shift
Speaker 1: key mode. It's called thirty one BOD by some people
Speaker 1: US as a sound card to generate the the rtt
Speaker 1: Y signals. Thirty one is the symbol rates Actually thirty
Speaker 1: one point twenty five bod designed for keyboard to keyboard
Speaker 1: communication typing at rates up the fifty words per minute.
Speaker 1: So that's fast enough for me because I couldn't type
Speaker 1: that fast and as referred to as BPSK thirty one
Speaker 1: QPSK since two audio tones, so there are now four
Speaker 1: possible phase combinations. Okay, so since PSK has two tones,
Speaker 1: you have to select the right sideband to the correct
Speaker 1: sideband here, either upper or lower. If you're in the
Speaker 1: wrong sideband, you're gonna you're gonna invert your tone, so
Speaker 1: you're not gonna decode it. So make sure you understand
Speaker 1: what band you're on. Usually it's upper sideband even no
Speaker 1: matter what band you're on for the for the digital modes,
Speaker 1: but if you're tuned in and you're not copying, swap
Speaker 1: sidebands and see if it starts reading correctly, so it
Speaker 1: is sideband sensitive. PSK uses a variable link character called
Speaker 1: very COODE that assigns shorter codes to common characters and
Speaker 1: longer codes for uncommon characters like Morse code, capital letters,
Speaker 1: and punctuation take longer decent if you're using If you're
Speaker 1: used to do RTTY with no lowercase, turn off caps
Speaker 1: lock because they take more. Something I didn't know for
Speaker 1: a while was I didn't know it was any different
Speaker 1: on you know, the character you sent, whether it's sent
Speaker 1: eight characters or three, was based on what you had tied.
Speaker 1: Good news. Really, I couldn't die types so slow. It
Speaker 1: didn't make any difference. But that's interesting fact there. So
Speaker 1: QPSK thirty one and PSK thirty one have about the
Speaker 1: same band with two point five killer hertz. QPSK is
Speaker 1: sideband sensitive and it's encoding provides error detection. So what's
Speaker 1: the most common frequency shift E mission on the amateur
Speaker 1: HF bands on the shift one hundred and seventy hertz
Speaker 1: number B letter B? Which of the following is characteristic
Speaker 1: of QPSK coding error corrections approximately the same? Sideband sensitive?
Speaker 1: I think all those sound right, that's correct. Which of
Speaker 1: the following describes a BOTTO code? It's a five big
Speaker 1: code at BC. Which of the following statements is true
Speaker 1: about PSK thirty one upp acase on use very coode
Speaker 1: b B with b B. Which type of code is
Speaker 1: used for sending characters in a PSK thirty one signal
Speaker 1: very code A? All right, talk about some packet based.
Speaker 1: These are structured modes and they're derived from early teletype
Speaker 1: over radio or computer to computer network systems. Hams have
Speaker 1: adapted the protocols creating packet radio, pack tool, win More
Speaker 1: and other communication systems. Some packet modes JT sixty five
Speaker 1: and FT eight require precisely defined transmission periods. The utility
Speaker 1: software is a able to keep your computer synchronized within
Speaker 1: one second of the standard time. So some of these
Speaker 1: modes like FT eight get you sixty five your your
Speaker 1: local time source is important to have it sync within
Speaker 1: a second of the guy you're talking to. So some
Speaker 1: of the basis of packet packet refers to the transmission
Speaker 1: of data and structured groups called frames. Packet communication systems
Speaker 1: package data with the package the data with control and
Speaker 1: routing information, and add error detection information. Each package or
Speaker 1: of header, data and trailers called the frame. Different packet
Speaker 1: protocols are used for different sets of information and mesags
Speaker 1: of creating the frame, but basically the same. You use
Speaker 1: to have a header the data, and you have some
Speaker 1: kind of trailers. The header contains the bit patterns that
Speaker 1: allow receivers to sync with the package structure, control of
Speaker 1: routing information in some then for some protocols, air detection
Speaker 1: correction data is the data is the data to exchange
Speaker 1: between the systems, usually asking characters, usually compressed for efficiency.
Speaker 1: The trailer vent is added on the information at the
Speaker 1: end for error detection. Forward error correction goes beyond simply
Speaker 1: detecting errors. By including redundant encoded info with the data,
Speaker 1: it's possible for receiver to correct certain types of data errors.
Speaker 1: Most common air detection mechanism is called a cyclic redundancy
Speaker 1: check or CRC. On an ARQ system, automatic repeat requests.
Speaker 1: If mismatched is detected, the receiving system responds with the knack,
Speaker 1: which not acknowledged and the proto the protocol request retransmission
Speaker 1: transmitting will continue to send. The transmitting system will continue
Speaker 1: to send pack it until it's received without air or
Speaker 1: retransmissions has reached a limit okay. ARQ is used in packtor,
Speaker 1: packet radio, and win more. ARQ protocols were used for
Speaker 1: wired network connections and the transmission can only be received
Speaker 1: from one receiving station during the connection. This means you
Speaker 1: can't break into a contact between two stations using ARQ.
Speaker 1: So if Jason and I are talking ARQ. Our systems
Speaker 1: are trying to talk to each other. If somebody else
Speaker 1: gets in there, we're not going to respond to them
Speaker 1: because we're trying to complete our handshakes. So that's what
Speaker 1: they're talking about here. You can't break If two stations
Speaker 1: are talking, don't try to break into them because you're
Speaker 1: not going to be acknowledged and you're just going to
Speaker 1: cause interference on what they're trying to do. So that
Speaker 1: a station can advertise as presence, however, ARQ protocols provide
Speaker 1: a broadcast mode to trans meant without another station having
Speaker 1: to established consonants UH contact, So so you can there's
Speaker 1: a there's a there's a mode where you just like
Speaker 1: calling c Q and a ar Q and if somebody
Speaker 1: here's it, their station will respond on the two view
Speaker 1: will pair up. I used to do this long time
Speaker 1: ago amp uh app's the app core UH long am
Speaker 1: I forgot what it's called long time ago. A mod
Speaker 1: mode is also provided so that stations can listen to
Speaker 1: the other stations without getting into their error correction scheme right.
Speaker 1: Using the moond mode allows you to determine if the
Speaker 1: frequency is occupied by two stations having an a ar
Speaker 1: Q mode contact. It's designed to transfer data between only
Speaker 1: two stations, mean that you can't break into the contact.
Speaker 1: Talked about that packet radio t R system developed to
Speaker 1: compensate for transmission errors and r t t Y used
Speaker 1: almost exclusively on the UHF bands, packet radios and shorts
Speaker 1: bursts of characters with error detection and correction data. It's
Speaker 1: based on computer network protocols x DOT two five, one
Speaker 1: of the oldest packet switching communications protocols popular during the
Speaker 1: late nineteen seventies and eighties. Back when I was learning
Speaker 1: about stuff that was that was slick stuff. Back in
Speaker 1: the day, packets exchange using VHF FM voice at twelve
Speaker 1: hundred and ninety six hundred BOB. Today we've got we've
Speaker 1: got some improvements over that. It does not work well
Speaker 1: with HF broadcasts because of the noise and fading and
Speaker 1: AHF you to have to be at three hundred bar
Speaker 1: or lower. HF UHF packets still big around here, works
Speaker 1: works good day. Pactor and win More so these reliably,
Speaker 1: I mean the rival they're kind of low, but they're
Speaker 1: reliable and they're robust. Packed tour is packet based to
Speaker 1: you are win More's win based to you are they
Speaker 1: work pretty well. Packed Tour one uses frequency shift King modulation.
Speaker 1: Packed Tour one through four use advanced PSK pack to
Speaker 1: four not yet legal for us amateurs, might be coming close.
Speaker 1: I mean there's there's legislation they're working on getting that,
Speaker 1: but it's a very good mode. They work fine. Pack
Speaker 1: Tor and Varro modes have overcome some of the issues
Speaker 1: with HF. I know, we use Vara on our packet
Speaker 1: system here. We do dual mode packet or the regular
Speaker 1: packet twelve twelve hundred bod. Varro works well and seems
Speaker 1: to be doing good round here. Okay. Win Link so
Speaker 1: win Link is a is a way to transfer email
Speaker 1: and messaging over HF. We use it VHF UHF here
Speaker 1: also for our areas work and it's a well established group.
Speaker 1: We've got several wind Link ports here in town and
Speaker 1: they work very well. And wind Link isn't a mode,
Speaker 1: it's a gateway communications system. It uses the Internet to
Speaker 1: connect it's email services with a gateway and mailbox stations
Speaker 1: around the world on HF. VHF and UHF said it's
Speaker 1: been around the wild, it's been improved a lot, and
Speaker 1: it's fairly reliable and all those fails. It's a good
Speaker 1: mode to get stuff going. Win Link stations did not
Speaker 1: connect directly to the Internet, but they provide a means
Speaker 1: for stations out of your local Internet coverage to connect
Speaker 1: in range. So that's pretty cool. If you have a
Speaker 1: regional outage somewhere, power data, fiber, oppet cables cut, no
Speaker 1: Internet allows you to connect RF to someone plays else
Speaker 1: that does have Internet connection. You can get your email
Speaker 1: and your data truth so even without Internet connectivity. Win
Speaker 1: Link Express, which is a program you can download, runs
Speaker 1: in a PC, can act as a standalone mailbox station
Speaker 1: or communicate directly with each other. You can do peer
Speaker 1: to peer connections. Done all that so on HF. Win
Speaker 1: Link uses pack Tour and Vara modes. Uh Var is
Speaker 1: the most popular, is the more popular. Vara is a
Speaker 1: tour software developed by e A five HBK software, So
Speaker 1: check that out. Okay, FT eight and whisper. These are
Speaker 1: called Wheat signal modes. They're supported by the WSJT software suite.
Speaker 1: A lot of cool modes in there. Here's a you
Speaker 1: can go check it out that They use eight tone,
Speaker 1: frequency shift, king modulation and air decoding. Correction to enable
Speaker 1: successful decoding. Very low signal to noise ratios. FT eight's
Speaker 1: and seventy five bit messages limits messages to call signs,
Speaker 1: good locations and signal reports only. FT eight signal reports
Speaker 1: are on the signal deloise ratio, so a report of
Speaker 1: plus three means the signal was three dB above the
Speaker 1: noise floor. We's com in FT eight. Transmission ranges are
Speaker 1: in fourteen seven four to fourteen seven seven. Be sure
Speaker 1: to locate a clear frequency and selected timeslot that doesn't
Speaker 1: interfere with the calling stations. Specifically when responding the clear
Speaker 1: frequency and the ultimate time slot so that used by
Speaker 1: the calling station. So FD eight's very popular. Done a
Speaker 1: lot of that that myself. It's a lot of fun Whisper.
Speaker 1: It's an HF propagation passed the week signal things. I
Speaker 1: run two Whisper notes from my home on thirty and
Speaker 1: twenty meters all the time. It doesn't support two way QSOs,
Speaker 1: but I have a beacon that transmits and all the time,
Speaker 1: and I can go look at signal reports and see
Speaker 1: who's seen my signal around the country. Spun built the
Speaker 1: Whisper nodes myself. Fairly easy to do, and it's fun
Speaker 1: to play with. Okay, low power Whisper transmitters generate coded packets.
Speaker 1: Stations that receive these reports can report them on the
Speaker 1: whispernet dot org and it's fun to go look at
Speaker 1: your signal reports and see what you can see. So okay,
Speaker 1: amateur wireless networks certain wireless networks. When networking frequencies overlap
Speaker 1: with amateur bands, amateurs are able to use them for
Speaker 1: many of the same purposes that under license users are
Speaker 1: able to, such as text messages, voice over IP, email,
Speaker 1: et cetera. If you operate a wireless network on FCC
Speaker 1: Part ninety seven frequencies, you must comply with the prohibit
Speaker 1: the prohibitions on encryption. HAM used two basic network topologies,
Speaker 1: Mesh and Star configurations, and advantage of the met network
Speaker 1: prot topology is that if one node fails, the packet
Speaker 1: may be able to find this destination by routing through
Speaker 1: another available node. So here's some wireless network frequencies that
Speaker 1: that we have that we can share and use. And
Speaker 1: in these bands, there are some HAM specific channels that
Speaker 1: are on our side, which really makes it nice. Arden
Speaker 1: is an amateur radio emergency data network. It's a mesh
Speaker 1: network can be made uses commercially available routers and the
Speaker 1: nine hundred two point four two point four five point
Speaker 1: eight giggers band Arden website one of the best websites
Speaker 1: I've seen for information and how to understand and get information.
Speaker 1: They do a great job. There's a go to the
Speaker 1: ardmesh dot org if you're inntioned in. That generally used
Speaker 1: during the emergency to support communication events like road races,
Speaker 1: parades and other large gatmies. But it uses that you
Speaker 1: can use the commercial items h put them into the
Speaker 1: handbands and they work. They weren't great, Let's see. It's
Speaker 1: a digital protocol users one link B. Which of the
Speaker 1: following is a good practice when using a transmittered frequency
Speaker 1: to answer a station calling CQ using FT eight UH,
Speaker 1: I think you want to call. You want to find
Speaker 1: a clear frequency during the same time slot as the
Speaker 1: calling UH and the ultimate timeslot as the calling stations
Speaker 1: that would be D. Which of the following is required
Speaker 1: when using FT eight You need a computer with accurate
Speaker 1: time within a one second. That's the key. B. How
Speaker 1: do you join a contact between two stations using the
Speaker 1: pack tool protocol UH? It is not possible see because uh,
Speaker 1: it's only limited to two stations, so see is it.
Speaker 1: What is the primary purpose of an amateur AIO data
Speaker 1: network mesh network. Let's c to provide high speed data
Speaker 1: services during emergency or a community event. Which of the
Speaker 1: following describes win Link. It's a wireless network capable of
Speaker 1: both VHF and HF band operation, form of packet radio
Speaker 1: and all those D. What is another name for a
Speaker 1: win link remote message server. It's called the gateway. Which
Speaker 1: of the following is a common location for FT eight.
Speaker 1: It's between fourteen oh seventy four and fourteen oh seventy
Speaker 1: seven C. What type of modulation is used by FT eight?
Speaker 1: It uses eight tone frequency shift key. Hey, what is
Speaker 1: QPSK modulation? It's modulation using let's see the angles, degrees,
Speaker 1: face shifts at the bottom. D. Which digital mode is
Speaker 1: used as a low power beacon for assessing HF propagation
Speaker 1: be a whisper node weak signal propagation. What part of
Speaker 1: packet radio frame contains the routing and handling information? That's
Speaker 1: the preamble. Excuse me, sorry, it's the header. The header
Speaker 1: has the UH. The information contained a routing handling information?
Speaker 1: Sorry about that? The header in an an ARQ mode.
Speaker 1: What is meant by NAC response to a transmitted packet?
Speaker 1: It means how does forward error correction allow the receiver
Speaker 1: to correct data errors by transmitting or doneant information? See
Speaker 1: what does an FD eight signal report of three plus
Speaker 1: three plus three means? That means it's three times the
Speaker 1: noise level? Yep, all right. Most digital modes on HF
Speaker 1: are transmitted as USB signals, the exception as rtt Y
Speaker 1: uses LSB modem and software must be configured for the
Speaker 1: correct moder rate receiving tone received data signal screen you
Speaker 1: know to be tuned correctly. Since PSK uses a single tone,
Speaker 1: either USB or LSB will work. Most use USB. Like
Speaker 1: other amateur signals. Digital mode bandwidth is defined by the FCC.
Speaker 1: The bandwidth of signal changes with symbol rate. The symbol
Speaker 1: rate increases, so does the bandwidth needed for the signal
Speaker 1: needed to transmit them. Most common method of generating transmitting
Speaker 1: these modes is to connect to an audio output of
Speaker 1: a computer sound card to the microphone of a single
Speaker 1: sideband transceiver. So most time you're going to use your
Speaker 1: computer to connect the sound card connect the tune radio.
Speaker 1: Here's a chart that shows some of the bandwidths of
Speaker 1: the different digital modes. What's interesting to point out here
Speaker 1: is like PSK thirty one and FT eight, they're fifty hertz.
Speaker 1: Why we don't send a lot of information there, but
Speaker 1: they're fifty hurts wide, so that means you could put
Speaker 1: fifty uh QSOs fifty times five. It's twenty five hundred
Speaker 1: in a you need some space, but you can put
Speaker 1: a bunch in a audio passband right. So sometimes you'll
Speaker 1: see in the FT eight modes just the whole past
Speaker 1: base is loaded, we'll sleep, so you can get a
Speaker 1: lot of QSOs in one. It's very efficient five percent
Speaker 1: of the time. But FM modes and these digital modes,
Speaker 1: you're transmitting full power the whole time that you're transmitting,
Speaker 1: and those times those can be you know, several seconds
Speaker 1: to half amended or something, so you have to be
Speaker 1: real careful. Make sure you watch your transmitter, don't ex seed.
Speaker 1: It's average power rating, so reduce the transmit power to
Speaker 1: prevent overheating. Usually I buy about fifty percent is usually
Speaker 1: a good idea. Digital modes can generate interference, just like
Speaker 1: phone and c W. For digital modes that use a
Speaker 1: single sideband transmitter to transmit audio FSK. Most common problem
Speaker 1: is supplying too much or too little audio from the
Speaker 1: computer to the radio's microphonium pit a waterfall display. The
Speaker 1: vertical lines represent spurrac emissions caused by overmodulation of the transmitter.
Speaker 1: ALC and digital modes Automatic level control are their use
Speaker 1: for preventing excessive drive to the amplifier inputs. ALC circuit
Speaker 1: produces gain when power level gets too high. However, it
Speaker 1: comes at a price. The signal compression can result in
Speaker 1: distortion resist temptation to turn up gain. For digital signals,
Speaker 1: distortion caused by ALC makes the signal harder to decode
Speaker 1: create spurase emissions. It's similar to overmodulation. When in digital mode,
Speaker 1: your ALC system should be either disabled or input level
Speaker 1: and gain turned down to the point where the ALC
Speaker 1: does not activate. So my experience operating this is or
Speaker 1: any of the digital mode. This is probably the most
Speaker 1: common airror mistake misunderstood piece by some new opera by
Speaker 1: operators they don't have their ALC their audio input adjusted right.
Speaker 1: You can turn it off. But what I do is
Speaker 1: I have mine turned on, but I have it right
Speaker 1: below where it cuts on like it, just like it says,
Speaker 1: so that seems to be the right sweet spot for me.
Speaker 1: But you can hear you can see a station when
Speaker 1: they're really over modulating their signal, their call sign will
Speaker 1: show up four times in the FT eight pass band, right,
Speaker 1: So this is probably the most important thing to go
Speaker 1: adjust and correct is get your audio levels right coming
Speaker 1: from your from from your PC. If you're using a
Speaker 1: Windows thing, Windows sometimes does favorite things to your sound
Speaker 1: card when you didn't want it to an update or something,
Speaker 1: so always check this and make sure you got an
Speaker 1: eye on. I always have my my ALC meter up
Speaker 1: on my so I can always see if something's going
Speaker 1: on there. ALC is a big is a big deal
Speaker 1: in digital modes, all right. It's send to some practice
Speaker 1: questions which mode is normally used when sending rtt Y signals.
Speaker 1: So rtt Y is almost always doing in lower sideband,
Speaker 1: and for the all the other digital modes it's usually
Speaker 1: upper sideband, which is bu What could be wrong if
Speaker 1: you cannot decode an RTTY or other FSK signal even
Speaker 1: though it apparently tuned in properly. Market space can be
Speaker 1: reversed wrong boderate wrong side I think all those sound
Speaker 1: correct to me, and that is correct? What should the
Speaker 1: ALC system? Why should the ALC system be active when
Speaker 1: transmitting AFK signals? Too much ALC can cause a transmitter
Speaker 1: to I think it's B. The ALC can action can
Speaker 1: distort the signal. Why is it important to know the
Speaker 1: duty cycle of the mode you're using when transmitting? Want
Speaker 1: to make sure you don't exceed your transmitter's average power
Speaker 1: rating or can be B. What is the relationship between
Speaker 1: transmitted symbol rate and bandwidth? Uh? The higher symbol rates
Speaker 1: require wider bandwidth, so that's B. What is indicated on
Speaker 1: a waterfall display by one or more vertical lines on
Speaker 1: either side of the data mode on an r TTU
Speaker 1: I signal, usually that's over modulation. Okay, let's talk about
Speaker 1: in a digital mode. How do we initiate a contact? Right? So, yeah,
Speaker 1: like a voice mode, You type in C Q c Q,
Speaker 1: this is my case, K M four CJ, save it
Speaker 1: a few times, put a K at the end saying hey,
Speaker 1: I'm waiting for someone to contact me that I'm over,
Speaker 1: and then the response station would say my call sign.
Speaker 1: This is followed by the answering station's call signed with
Speaker 1: the K at the end. Modes such as pactor and
Speaker 1: VARA the software mode and will have a specific disconnect message.
Speaker 1: But notice the K here to use at the end
Speaker 1: of a transmission to indicate the other station is to
Speaker 1: transmit as shown, so that says that I'm finished waiting
Speaker 1: on you. Right. It's like over if you connect to
Speaker 1: a gateway. The exact way you connect to the gateway
Speaker 1: depends on the equipment and the mode that you're using,
Speaker 1: but us it begins with some kind of a connect message.
Speaker 1: If the signal is received without air, there's usually a
Speaker 1: handshaking or right. They call it training sequence and packets
Speaker 1: to help for the two stations to determine the right
Speaker 1: road the VOD in the protocol to use. Because these
Speaker 1: stations respond without a human control operator they are operating.
Speaker 1: A lot of them are automatically run, so they have
Speaker 1: to fall under the rules of the digitally controlled Automatically
Speaker 1: Digitally controlled station rules, which restricts them to certain parts
Speaker 1: of the band and stations under FCC rules must operate
Speaker 1: under local remote control with control operator in charge of
Speaker 1: all transmissions. That's the rule. Here's where you can find
Speaker 1: on the band plan these automatically controlled digital stations are
Speaker 1: allowed to operate here. Then during the contole. A waterfall
Speaker 1: is kind of a neat display. It shows yours all
Speaker 1: the nearby signals. This is a PSK thirty one looks
Speaker 1: like The waterfall displays a series that shows the presence
Speaker 1: of signals and the series of lines representing the scan
Speaker 1: across the frequency range. Signal strengths is represented by brightness
Speaker 1: or density or color. As new lines are captured, older
Speaker 1: lines are removed as it moves down. The slides down
Speaker 1: the screen. It's called the waterfall tuning age for an
Speaker 1: RTTY signal. If I've got looking at an RTTY signal
Speaker 1: on a spectrum analyzer or or my audio spectrum analyzer,
Speaker 1: the vertical lines are the mark and the space. Uh
Speaker 1: those are these lines right here and help tune in,
Speaker 1: so you would tune across the band. You're going to
Speaker 1: line up your as you move this wiggly line across
Speaker 1: you want to line them up to these right here
Speaker 1: and helps you tune in the signal. There's a also
Speaker 1: you can look on a silloscope kind of thing and
Speaker 1: see the crossed ellipse from the right. They're used to
Speaker 1: to see how well fine tuned if you're perfectly tuned,
Speaker 1: you'll see two ellipses perfectly at ninety degrees angles. That
Speaker 1: indicates how good your tuning is going. That's a pretty
Speaker 1: good looking signal there. Okay. Third party traffic. All the
Speaker 1: rules about third party traffic apply to digital transmissions. You know.
Speaker 1: That includes the information and the emails, the digital messages.
Speaker 1: If you transmitter a web page or whatever kind of thing,
Speaker 1: third party rules still apply. Commercial messages may not be
Speaker 1: transmitted via amateur radio, so interfering signals in digital modes
Speaker 1: hidden transmitters. If I'm talking to a guy over in
Speaker 1: Europe FT eight, I don't hear I don't. I only
Speaker 1: hear him, But over in Europe he may be hearing
Speaker 1: three or four guys on the same frequency I'm on,
Speaker 1: but I can't hear them, so I may have a
Speaker 1: hard time talking to him. So that's sort of what
Speaker 1: referred to as he's hidden to me. It's okay. The
Speaker 1: result is unintentional, but it prevents us from uh from
Speaker 1: completing the contact. Unpacket modes, packed tour or when more,
Speaker 1: they don't recover well from noisy and weak signal week environments,
Speaker 1: so you get a lot of failure If you get
Speaker 1: a lot of failure to connect or frequently tried after
Speaker 1: a long time, it may just be band conditions are
Speaker 1: too noisy, try a different band or something like that.
Speaker 1: So here's some practice questions for this section. What's required
Speaker 1: to conduct communications with the digital station operating automatic control
Speaker 1: outside the automatic control band segments, It's gonna be a
Speaker 1: the station is shame and the contact must be under
Speaker 1: local or remote control. Same rules that apply for voice
Speaker 1: for controlling the station UH with the automatic control. And
Speaker 1: what bands may automatically controlled stations transmit RTTY or data
Speaker 1: missions communicated with other controlled stations. I think only on
Speaker 1: the band's segment where it's permitted anywhere in the six
Speaker 1: meter or shorter wave. The bands are limited segments, that
Speaker 1: is corrected its specifically to on the six meter band
Speaker 1: on this particular one UH. These are automatically controlled stations
Speaker 1: transmitting rtt y. You know, two of them in only
Speaker 1: one place you can do it, that's the six meter band.
Speaker 1: What symptoms may result from the other signals interfering with
Speaker 1: the pactor or VARA transmission? What symptoms frequent retries, long pauses,
Speaker 1: failure to establish connection between those all those symptoms that
Speaker 1: we've got interfer in the signals. Okay, Which is the
Speaker 1: following is a way to establish contact with the digital
Speaker 1: messaging gateway system. Uh, you don't send EMO to the
Speaker 1: control operator transmits it's a connect message is how you
Speaker 1: It's how you try to connect to them. Be deep?
Speaker 1: What action results from a failure to exchange information due
Speaker 1: to excessive transmission attempts when using an ar Q mode?
Speaker 1: I think connection has dropped. That's correct, because they're gonna
Speaker 1: there's a time out time or you're gonna try to
Speaker 1: talk to somebody. If you're talking to them and somebody
Speaker 1: you lose connections, there's a number of retries and then
Speaker 1: it gives up. So that's that's that's me. Which of
Speaker 1: the following describes a waterfall display? Let's see frequency is
Speaker 1: uh is vertical, amplitude is horizontal signal strength Uh, let's
Speaker 1: see signal strength time the C frequency spour is horizontal
Speaker 1: signal strength tensity. It is all vertic. Right, And that's
Speaker 1: the end of this chapter. M So you want to
Speaker 1: do another module? You want to stop for today? It's
Speaker 1: not loud and here, yeah, I think it is loud. Guy,
Speaker 1: that sounds good. I'm Okay, so that was the Okay,
Speaker 1: Our next topic we're going to talk about is UH.
Speaker 1: Here is dipoles, ground planes and yaggy antennas. The most
Speaker 1: fundamental antenna we have in AMATE radio is a dipole UH.
Speaker 1: It's a straight conductor that's half wave linked UH along
Speaker 1: with the feed point in the middle. It's also known
Speaker 1: as a double it antenna UH. The strongest radiation direction
Speaker 1: of the dipole's broadside to its axis and a plane
Speaker 1: containing the ant and its conductor. The weakest radiation is
Speaker 1: off the ends. The shape of asthmith pattern for a
Speaker 1: dipole and free space is shown in the next figure.
Speaker 1: And I'll show you here's the picture. This is what
Speaker 1: it looks like. Again. You've got a halfway link piece
Speaker 1: of wire feeding it in the center, stretched out for
Speaker 1: horizontally and this is the radiation patterns you can see.
Speaker 1: It has a radiation pattern broadside and to the back
Speaker 1: with a less radiation to the sides. So very fundamental antenna.
Speaker 1: Great antenna probably the most popular type of antenna we
Speaker 1: have to using in the HF bands. Okay. Diepole is
Speaker 1: often used as a reference antenna for gain measurements. Gain
Speaker 1: is measured in DBD. Isotropic antenna is a reference antenna
Speaker 1: with a gain given in dbi. The isotropic antenna is
Speaker 1: a theoretical antenna. It's an a tenda that radiates equally
Speaker 1: in all directions. So sometimes you'll see U an antenna
Speaker 1: the performance reference to dB I or just dB with
Speaker 1: the gains. So there's a way to convert between the two.
Speaker 1: To convert from dB D which is dB dipole the
Speaker 1: dB I, which is isotrophic, as you add two point
Speaker 1: one five dB h to convert dB I to dB
Speaker 1: D uses to subtract two point one five dB. Current
Speaker 1: in a halfway dipole is highest in the middle, that
Speaker 1: is in zero at the ends. Voltage along the dipole
Speaker 1: is highest at the ends and lowest in the middle.
Speaker 1: So if you have a dipole antenna, just remember that
Speaker 1: that the current is the highest in the middle, voltage
Speaker 1: is in lowest in the ends, and the and the
Speaker 1: voltage is the opposite. The halfway diepole, as we see
Speaker 1: here in this figure, has its maximum current at the
Speaker 1: middle U and the maximum excuse me has a minute.
Speaker 1: It has a maximum current in the middle of maximum
Speaker 1: bolted at the end. The feed point impedance is lowest
Speaker 1: in the middle. The odd harmonics of the fundamental frequency
Speaker 1: of the dipold speed point impediance is low at the midpoint.
Speaker 1: Once again has shown So if you've got harmonics, this
Speaker 1: is what they would look like based on if it's
Speaker 1: a half, if it's a second, third, fourth harmonic. So
Speaker 1: again the impedance is lowest in the middle for us
Speaker 1: for the this dipole, and typically dipoles about sixty eight
Speaker 1: sixty two homes. The impedance increases as a feed point
Speaker 1: is moved away from the center several thousand homes at
Speaker 1: the end. Popular antennas are in FED halfway off center,
Speaker 1: FED halfway. You'll hear a lot of those. Those are
Speaker 1: different variations of where you feed the end the antenna.
Speaker 1: The FED as an example as popular for porta bowl operation.
Speaker 1: It's a lightweight, easy to install. It's a halfway dipole
Speaker 1: fed at one end. In free space. The half wavelength
Speaker 1: is equal to about four hundred and ninety two divided
Speaker 1: by the frequency in megahertz. This is if you want
Speaker 1: to get the linked and feet you'll generally find that
Speaker 1: the length will be shorter than the free space wavelength.
Speaker 1: Calculation However, for these exam questions you don't have to
Speaker 1: take that into account. Just be aware that where thickness
Speaker 1: and hightabo bround influenced the resonant length and the length
Speaker 1: again in feet four hundred and ninety two divided by
Speaker 1: the frequency and wavelength. So what is the proximate length
Speaker 1: of in feet of a halfwave dipole resident of three
Speaker 1: point five to five megahurts? How would you calculate that? Well,
Speaker 1: remember we take our four hundred and ninety two divided
Speaker 1: by three point five to five and you get one
Speaker 1: hundred and thirty nine feet, So that would be the
Speaker 1: wavelength forty meters on eighty meters. Remember the axual antenna
Speaker 1: will be a little shorter than this, But build to
Speaker 1: that calculation and use your tuner to tell if it
Speaker 1: needs trimming. Ideally you won't. You want SWR as close
Speaker 1: to one to one as you can without tuning. So
Speaker 1: what's the approximate length and feet of a half wave
Speaker 1: dipole at fourteen point twenty five megahurts? This will be
Speaker 1: twenty meters, So remember to use your formula four ninety
Speaker 1: two divided by fourteen point twenty five and you get
Speaker 1: thirty four point five feet UH. Center fed dipoles are
Speaker 1: the easiest to use on the band which they are resident.
Speaker 1: The feed point impedance is a good match for a
Speaker 1: fifty or seventy five ONEm coax and for coacts on
Speaker 1: odd multiples of the fundamental frequency. A dipole doesn't need
Speaker 1: to be straight to be effective. Dipole can be supported
Speaker 1: in the center, where the feed line can be conveniently attached.
Speaker 1: There's another configuration called an inverted V, where you take
Speaker 1: the ends and lower them down. As long as the
Speaker 1: legs of the dipole form an angle of ninety degrees
Speaker 1: or more. The inverted V is nearly as effectively as
Speaker 1: a horizontal installed dipole. So how you fix your dipole,
Speaker 1: or how you based on the area that you've got
Speaker 1: to or the place you have to mount your antenna
Speaker 1: is going to determine a lot what's going to be
Speaker 1: the shape of your dipole. But don't worry too much
Speaker 1: about trying to keep it perfectly horizontally or you know,
Speaker 1: get your antenna up, tune it, get on the air.
Speaker 1: The ground plane antenna is one half of a dipole,
Speaker 1: with the missing portion made up by an electrical mirror
Speaker 1: or so we call that the ground plane. It's made
Speaker 1: from sheet metal or screen of the radios can be excused.
Speaker 1: The ground plane can be made from metal or a
Speaker 1: screen of radial wires. Basic ground plane is a quarterwave
Speaker 1: length long, with the feed point at the junction of
Speaker 1: the antenna and the ground plane. For HF ground playing
Speaker 1: antennas at ground level, radio wires are laid on the
Speaker 1: surface of the ground, or can be. They can't be
Speaker 1: buried within a few inches of the surface. Ground plays
Speaker 1: are called verticals because that's usually the way, uh that's
Speaker 1: usually the way they're constructed, and how you install them.
Speaker 1: A ground plane radiates the best broadside to its axis
Speaker 1: if installed vertically. The ground plane antenna pattern is omni directional,
Speaker 1: that is, its uniform in all asthmus angles or directions.
Speaker 1: Very useful for VHF and UHF mobile portable communications where
Speaker 1: the signals can maybe even where the signals they come
Speaker 1: from any direction. Here's a here's a picture of a
Speaker 1: ground play. Again. You've taken that diepole and you've made
Speaker 1: you've made it a quarterwavelength tall, and uh, you've taken
Speaker 1: the other half of the diepole you've made that your
Speaker 1: plane now. So the ground plane, whether made of solid
Speaker 1: metal or radio wires, creates an electrical mirror the image
Speaker 1: of the quarterwave antenna. This creates the electrical the electrical
Speaker 1: equivalent of a dipole antenna. The feed point impedance at
Speaker 1: the base of an ideal ground plane it's about thirty
Speaker 1: five omes half of a complete dipole's impedance. Because only
Speaker 1: half of the antenna is physically they're able to radiate
Speaker 1: the enter the energy. So remember the dipole center fed
Speaker 1: dipole is about sixty to sixty three ohs. The feed
Speaker 1: point and penants of a ground plane antenna with the
Speaker 1: radios perpendicular to the antenna proxy, thirty five omes resulting
Speaker 1: in a one point four to one SWR with a
Speaker 1: fifty oem coax fee. Drooping or sloping the radios gradually
Speaker 1: raises the feed point impedance until until the radios droops
Speaker 1: so far as to become only one half of the dipole.
Speaker 1: The feed point pediants becomes seventy two oms, so a
Speaker 1: fifty O feed point is reached with radios grouping approximately
Speaker 1: forty five degrees. These are real popular for vhf uhf.
Speaker 1: They're easy to make, and you just put your quarterway
Speaker 1: whatever your two meters or two twenty or four to
Speaker 1: forty and then do your ground radios and vend them
Speaker 1: slightly forty five degrees and they work great. You can
Speaker 1: put them in your in a closet in the attic
Speaker 1: and they're great antennas. Then a droop angle three to
Speaker 1: forty five degrees was shown in the last figure. It
Speaker 1: results in a feed point penance approximately cook approximing fifty oms.
Speaker 1: As with the dipole, it's not useful to provide a
Speaker 1: one size fits all formula for the length of the
Speaker 1: ground plane antenna. Since the ground plane is one half
Speaker 1: the size of a diepole. Start with one half the
Speaker 1: free space length and be prepared to trim the antenna's link.
Speaker 1: So you always want to start longer than you need
Speaker 1: because once you start trimming antenna sometimes it's difficult to
Speaker 1: go back the other way. So what's what's what's the
Speaker 1: approximate length and feet of a quarterwave monopole antenna cut
Speaker 1: for twenty eight point five megaherts. So remember a quarterwave,
Speaker 1: you're gonna use two hundred and forty six divided by
Speaker 1: the frequency, so two hundred and forty six it's a
Speaker 1: quarterwave two forty six divided by twenty eight point five
Speaker 1: eight point six feet, So a ten meter UH quarterway
Speaker 1: vertical is about eight and a half feet all right,
Speaker 1: HF mobile HF and antennas UH they're often some ford
Speaker 1: of a ground plane UH. Most popular is the vertically
Speaker 1: oriented whip antenna for mobile operation. A full sized quarterway
Speaker 1: mobile whip, though, is really not feasible on bands below
Speaker 1: twenty eight twenty four megaherts just too long, so you
Speaker 1: often you'll see what what what they call loading. There's
Speaker 1: some loading techniques that are used to increase the electrical length.
Speaker 1: Usually sometimes you'll see loading coils, a coil added to
Speaker 1: the base or or somewhere along the length. Sometimes you'll
Speaker 1: see what's called capacitive hats their spokes or look like
Speaker 1: a wheel shaped structure added near the top of the antenna.
Speaker 1: And then there's linear loading whereus part of the antenna
Speaker 1: is folded back on itself. So these techniques are all
Speaker 1: devised to load the antenna to make it think it's
Speaker 1: electrically longer than it really is. Another common feature of
Speaker 1: mobile whips is the corona ball at the tip. It
Speaker 1: does add a small amount of loading capacitance, but its
Speaker 1: main purpose is to eliminate high voltage discharged from the
Speaker 1: sharp tip of the antenna while transmitting A loaded antenna
Speaker 1: is not as efficient as a full size straight whip,
Speaker 1: and we'll have a small operating band without without retuning.
Speaker 1: When you add a loading coil to an end to
Speaker 1: an antenna puts a real high que in that area
Speaker 1: of the band that you're operating in. So if you
Speaker 1: if you've got a large band, you may have to
Speaker 1: retune it to as you've moved throughout the band because,
Speaker 1: like I said, it's it's tuned for a it's got
Speaker 1: a very narrow high queue on it. The screwdriver antenna design,
Speaker 1: which is a whip with an adjustable coil at the base,
Speaker 1: changes the inductance. It has gained popularity for HF mobile operation.
Speaker 1: Is a good compromise between performance and convenience. And you
Speaker 1: may have seen them. There's a big coil at the
Speaker 1: base and as you've moved between the bands, the coil
Speaker 1: moves up and down, changing the inductance. Pretty effective antenna. Great,
Speaker 1: Like I said, great, great compromise antenna for HF mobile operations.
Speaker 1: So what's the effects of ground on these antennas. A
Speaker 1: dipoles feed point impedance and radiation pattern are both affected
Speaker 1: by its physical height above ground. The feedpoint impedance is
Speaker 1: affected because the electrical image is electrically reversed from the
Speaker 1: actual dipole. As the image and antenna get closer to together,
Speaker 1: the actual antenna begins to be shorted out by the image.
Speaker 1: So below a quarter wavelength and height dipoles feed point
Speaker 1: and penis steadily decreases until it's close to the ground level.
Speaker 1: It's going to be close to zero. So so it's
Speaker 1: important to get the ground to get the antenna at
Speaker 1: least usually half a wave length up if if, if
Speaker 1: you can. Sometimes you can't do that, and I always
Speaker 1: say do the best you can. Try to meet the
Speaker 1: you know, the guidelines, but get it, get something up,
Speaker 1: get on the air. That's the main that's the main thing.
Speaker 1: This this chart here shows the feed point penions of
Speaker 1: a horzonal dipole over perfect ground and see it varies
Speaker 1: dramatically with the height at ground level down here to
Speaker 1: the bottom it's shorted out. Basically it's zero and see
Speaker 1: antenna moves up gradually it approaches about seventy two oms
Speaker 1: about feed point penance in free in free space above
Speaker 1: a quarter of the above one quarter wavelength impedance varies
Speaker 1: as suggested in this figure over here, eventually reaching a
Speaker 1: stable value at a height of several wavelengths. So you know,
Speaker 1: so eventually as you get it hired and hire it
Speaker 1: finally stabilizes up here. About seventy two oms is the
Speaker 1: feed point and penance when you get it real high,
Speaker 1: so uh fifty oms. Feed point impedance you can see
Speaker 1: here is about point two wavelengths above. So this chart
Speaker 1: just shows that that the height above ground is going
Speaker 1: to change it then the feed point penance, so you
Speaker 1: have to you have to compensate for that. High above
Speaker 1: ground also affects the radiation pattern because of reflection of
Speaker 1: the antenna's radiated energy by the ground. The direct and
Speaker 1: reflected signals take different amounts of time to travel to
Speaker 1: the receiving antenna, so they can add together, cancel each other,
Speaker 1: or any combination in between. So what happens when a
Speaker 1: dipole is raised in steps from a very very low
Speaker 1: height to more than one wavelength above ground And this
Speaker 1: figure shows some of those. These are four or four
Speaker 1: plots at different wavelength heights above ground. As a dipole
Speaker 1: starting at at one eighth wavelength above ground is raised,
Speaker 1: the effects of its electrical ground image caused the elevat
Speaker 1: elevation pattern to flatten out at multiples of the half wavelengths.
Speaker 1: The height pattern has a null in the inverted direction
Speaker 1: because the direct and reflected signals canceled at heights below
Speaker 1: half wavelength. The Dipolese pattern is almost omnidirectional and is
Speaker 1: maximum straight up, so the height above ground will change
Speaker 1: your radiation pattern of your diet of your dipole. There's
Speaker 1: another intendant called end VIZ, which is near vertical incident
Speaker 1: skywave propagation. These signals that these are signals that go
Speaker 1: straight up. UH signals radiated at high vertical angles on
Speaker 1: low frequencies are usually reflected back in the ground over
Speaker 1: a wide area, ensuring good communication. Horizontal dipoles from one
Speaker 1: tent to quarter wavelength high I produce an omnidirectional high
Speaker 1: out angle pattern ideal for envis opper ideal for the
Speaker 1: envas used like the previous chart showed, when that antenna
Speaker 1: got close to the ground, you saw the radiation pattern
Speaker 1: go more up in a round ball up towards the sky.
Speaker 1: So by lowering your antenna you can change the effect
Speaker 1: of its radiation pattern and use it to bounce off
Speaker 1: the sky and talk regionally. It's used by many public
Speaker 1: service teams. Polarization also affects the amount of signal that
Speaker 1: is lost from the resistance of the ground. Radio waves
Speaker 1: reflected from the ground have lower loss when the polarization
Speaker 1: of the wave is parallel to the ground that is
Speaker 1: horizontally polarized. Because the radiation pattern is made up of
Speaker 1: reflected waves, Combining the direct waves that are not reflected
Speaker 1: reflection loss results in stronger maximum signal strength. So here's
Speaker 1: some antenna terms. Feed point impedance that's the ratio of
Speaker 1: RF voltage to current and an antenna speed point resonant.
Speaker 1: When an antenna feed point impedance is completely resistant with
Speaker 1: no reactants, we talked about that yesterday. A little bit
Speaker 1: radiation pattern graph of antennas signal strength in every direction
Speaker 1: or at every vertical angle. That's a radiation pattern. The
Speaker 1: as myth pattern shows signal strength in the horizontal directions.
Speaker 1: Elevation patterns shows signal strength in the vertical direction. Lobes
Speaker 1: is a region in the radiation pattern where antenna is
Speaker 1: radiating a signal. Okay, that's the lobe, and then the
Speaker 1: nulls are the points at which radiation is that it's
Speaker 1: a minimum isotropic antenna radiates equally in all possible directions.
Speaker 1: Omni directional antenna radiates a signal equally in every horizontal direction.
Speaker 1: A directional antenna radiates provincially in one or more directions.
Speaker 1: Gain is a concentrated transmitted or received signals in a
Speaker 1: specific direction. Front to back ratio is a ratio of
Speaker 1: gain in the preferred or forward direction to the opposite direction,
Speaker 1: and front the side ratio is the ratio of gain
Speaker 1: in the preferred or four direction to directions at right angles.
Speaker 1: So those are some antenna terms that that that you
Speaker 1: will run into you if you look at an antenna
Speaker 1: spect some some of these things are spect out there
Speaker 1: and some of these things depending on what you're trying
Speaker 1: to do. These are important things that you'll need to
Speaker 1: consider choosing and the type of antenna that you want
Speaker 1: to use. Okay, what's the purpose of a capacity's hat
Speaker 1: on a mobile antenna? Do you remember that's the little
Speaker 1: ball that's up at the top of the vertical. Its
Speaker 1: primary it's primary thing is to u to increase the
Speaker 1: power handling capacity of a whip. Nope, that's not it
Speaker 1: reduced raition resistance to electrically LinkedIn. It's physically shorten the
Speaker 1: antenna to lower the variation angle have to be c
Speaker 1: but its primary purpose remember too, is to static discharge.
Speaker 1: What is the purpose of the corona ball. The same
Speaker 1: thing on the HF mobile antenna, and that's to reduce
Speaker 1: RF voltage discharged from the tip of the antenna while
Speaker 1: transmitting D So what is one disadvantage of using a
Speaker 1: shortened mobile antenna as opposed to a full sized antenna.
Speaker 1: Let's see, that's the operating bandwidth may be very limited,
Speaker 1: right because usually you don't have a full size antenna.
Speaker 1: You get your gonna going to shorten it. And to
Speaker 1: make it too, you used to put a coil in
Speaker 1: and that's gonna really affect where you can operate in
Speaker 1: that particular band because it's a high Q circuit, which
Speaker 1: is the following is a common way to adjust the
Speaker 1: feed point impedance of an elevated quarterwave ground plane CLI
Speaker 1: intendent to be approximately fifty OS. Remember we talked about there.
Speaker 1: This is where you take those ground radios. We've got
Speaker 1: a vertical now. And if you bend them, if you
Speaker 1: bend them down just a little bit, uh, bend them
Speaker 1: slightly downwards, Uh, that will help raise the input, the
Speaker 1: the raise the impediance. So it's which is the following
Speaker 1: best describes a radiation pattern of a quarterway ground plane
Speaker 1: vertical antenna, so about a quarterway round plane, and it
Speaker 1: is it's omni directional. What is the radiation pattern of
Speaker 1: a dipole antenna and free space and a plane containing
Speaker 1: the conductor? Okay, so that would be it's a figure
Speaker 1: eight at right angles to the antenna. So you're you
Speaker 1: remember it's the radiating is broadside to the antenna up,
Speaker 1: not broadside, but forward and back to the anti antennae.
Speaker 1: It's antenna itself. How does antenna hype affect the asthmathyl
Speaker 1: radiation pattern of a horizontal dipole HF antenna at elevation
Speaker 1: angles higher than about forty five degrees? So this is
Speaker 1: how does the height affect it? The antenna is less
Speaker 1: than a half wave link of that's sort of the
Speaker 1: key point. Hi, the asthma pattern is almost omni directional.
Speaker 1: You get lower than that, it starts flattening out. So
Speaker 1: see is the answer. Where should the radio wires of
Speaker 1: a ground mounted vertical antenna system be placed, let's see,
Speaker 1: on the surface or buried a few inches below the ground.
Speaker 1: So if you do in the parks, not in the air,
Speaker 1: lay them on the surface of the ground, that works. That,
Speaker 1: That works great. If you've got a permanent inflation at
Speaker 1: your house, you may want to bear them a little bit.
Speaker 1: You don't run open with the lawn with the lawn more,
Speaker 1: but don't bear them, don't bury them too low. How
Speaker 1: does the feed point impedant of a horizontal half wave
Speaker 1: dipole attended change as the antenna height is reduced to
Speaker 1: one tenth of its wavelength above ground? Okay, so if
Speaker 1: you as the the feed point is going to change,
Speaker 1: it's gonna get it's gonna decrease as you change the height.
Speaker 1: When you it it comes closer to the ground, the
Speaker 1: few point pens is gonna get. It's gonna get lower.
Speaker 1: Eventually get on the ground, it goes to zero. How
Speaker 1: does the feed point pence of a halfway dipole change
Speaker 1: as the feed point is moved from the center towards
Speaker 1: the end. So the feed point penance you remember of
Speaker 1: a center fed dipoles around sixty something else, the more
Speaker 1: you move it off of the center clos to the edge,
Speaker 1: it increases. So the a the impediance of an infed
Speaker 1: diepoles about twenty five hundred homes off center fed use
Speaker 1: the quarterwave, then it's about two hundred or two. It's
Speaker 1: about got about two hundred homes. So as you go
Speaker 1: from the center to the end, the few point pace increases.
Speaker 1: Which of the thowing is an advantage of a horizontally
Speaker 1: polarized as compared to vertically polarized antenna. Lower you have
Speaker 1: lower ground losses. What is the approximate length of a
Speaker 1: half wave dipole antenna cup? For fourteen point twenty five,
Speaker 1: So number's four ninety two divided by fourteen point twenty five,
Speaker 1: twenty meters is going to be about thirty three feet.
Speaker 1: All right, there's there's the equation four ninety two divide
Speaker 1: by fourteen point twenty five, it's thirty four point five,
Speaker 1: So thirty four point five in an answer, But you're
Speaker 1: gonna you're gonna get the closest one, which is D three.
Speaker 1: What is approximate wavelength of a half wave dipole antenna
Speaker 1: cup for three point five to five, it's going to
Speaker 1: be about one hundred and thirty two feet, all right,
Speaker 1: so remember take fortety two divided by the frequency to
Speaker 1: the half wave length that's going to be answered. Okay,
Speaker 1: how about we got a quarterwave. Now, remember just sitt
Speaker 1: in a halfwave, so it's not four ninety two, it's
Speaker 1: a quarterwave. So it's going to be two forty six
Speaker 1: divided by the frequency. In this case it's about eight feet.
Speaker 1: So when they ask these questions, you got to are
Speaker 1: they ask them for the halfwave which is four ninety
Speaker 1: two or the quarterwave which is half of that two
Speaker 1: forty six? So keep that in mind when you see
Speaker 1: this question. Are they asking for the halfwave or the Quarterwavey?
Speaker 1: How does antenna gains? State it in DBI compared to
Speaker 1: the game stated in dB for the same antenna. So
Speaker 1: the relationship is two point one five dB. But is
Speaker 1: it higher or or or lower? And this in this
Speaker 1: case it's actually higher. How does an antenna gain if
Speaker 1: you have a DBI antenna compared to a DVD which
Speaker 1: is a dB dipole, it's two point one five higher.
Speaker 1: Which of the following antenna types will be most effective
Speaker 1: as a near vertical incident skywave in is antenna short
Speaker 1: skip communications on forty meters during the day. Okay, horizontal
Speaker 1: dipole places one hundred and ten to one quarter wavelength
Speaker 1: above ground, a quarter to a half half above it's
Speaker 1: going to be a horizontal dipole, and it's going to
Speaker 1: be Remember, the closer you get to the ground, the
Speaker 1: more the radiation patterns is elevated up, so it should
Speaker 1: be a here it is, so let's ten a quarter
Speaker 1: wave to a tenth. Closer you get to the ground,
Speaker 1: the more radiation is going to be reflected up to
Speaker 1: the sky. Okay, what is the feed point impedance of
Speaker 1: an INFED half wave antenna. Let's see INFED is going
Speaker 1: to be two twenty five hundred homes, so we'd say
Speaker 1: very high in this case. D How does a screwdriver
Speaker 1: mobile antenna adjust its feed point impedance? It varies the
Speaker 1: loading with an end with the inducted so you'll see
Speaker 1: a coil at the bottom and it moves up and down.
Speaker 1: That coil is an is an inductor, so will be
Speaker 1: it varies in the inductance B. What is the common
Speaker 1: name of a dipole with a single central support. It's
Speaker 1: the inverted B configuration. Okay, let's talk about yaggy antennas.
Speaker 1: Directional antenna just create gain as well as rejecting interference
Speaker 1: and noise from other than the desired direction. By aiming
Speaker 1: your antenna in the direction shown in the asmithal projection map,
Speaker 1: you'll be beaming your signal directly at the other station.
Speaker 1: So as you point your antenna, that's the direct On
Speaker 1: a yaggy antenna, the where you point it, that's the
Speaker 1: direction your energy is going. Dipole, ground plane and random
Speaker 1: wire antennas use a single radiating element, but a dipole
Speaker 1: is an arrayed antenna. It uses two or more elements
Speaker 1: to create a maximum field strength in a specific direction.
Speaker 1: It's called the main lobe or major lobe of the
Speaker 1: radiation pattern. Two tie of arrays. There's the driven pair
Speaker 1: and parasitic and a driven array. All the antenna elements are
Speaker 1: connected to the transmitter and are called driven elements. Parasitic
Speaker 1: array one or more of the elements are not connected
Speaker 1: to the feed line but influence the antennas patterned by
Speaker 1: interacting with the radiated energy from the driven elements. Whether
Speaker 1: an array is driven or parasitic, it creation pattern is
Speaker 1: determined by the constructionive and destructive interference. If in phase,
Speaker 1: they will reinforce each other, out of phase, they will cancel.
Speaker 1: Most popular of all direction antennas is the yaggy because
Speaker 1: of its simple construction and good performance. Yaggy is a
Speaker 1: parasitic array with a single driven element in at least
Speaker 1: one parasitic element. The driven element is a resident dipole
Speaker 1: approximately halfwave length long. Parasitic elements placed in the direction
Speaker 1: of the maximum gain are called directors and the and
Speaker 1: are slightly shorter than the driven element. Parasitic elements in
Speaker 1: the direction of the minimum gain are called reflectors and
Speaker 1: are slightly longer than the driven element. The front to
Speaker 1: back ratio is the ratio of signal strength to the
Speaker 1: peak of the radiation patterns major lobe and that it
Speaker 1: and that to that and the exactly the opposite direction.
Speaker 1: So the front to back ratio is how much energy
Speaker 1: goes forward versus how much energy goes back. Okay is
Speaker 1: two element yaggy shown in this picture. Here with a
Speaker 1: single parasitic element, you can see we've got a driven
Speaker 1: element here, that's your dipole. You've got a director, this
Speaker 1: is the direction of radiation, and you've got a reflector
Speaker 1: in the back. So this is the way the antennae
Speaker 1: is obstructed, the way that it works. Yaggy design trade offs.
Speaker 1: Primary variables for Yaggy antennas are length and diameter of
Speaker 1: each element and their placement along the boom of the antenna.
Speaker 1: These affect the gain s WR front to back ratio
Speaker 1: in different ways. The more directors you have this increases
Speaker 1: the gain. A longer boom with the fixed number of
Speaker 1: directors increases gain up to the maximum length, beyond which
Speaker 1: gain is reduced. Larger diameter elements reduce SWR variation. With
Speaker 1: frequency placing and tuning of elements effects gain and feed
Speaker 1: point impedance. So all those factors come into play when
Speaker 1: you're trying to design your and your antenna. There are
Speaker 1: other general rules of cause and effects, but these are
Speaker 1: typically on decision of the antenna designer yourself. But when
Speaker 1: you go purchase Yaggy and Yaggy antenna, someone has already
Speaker 1: figured out the size of the beam and the size
Speaker 1: of the directors, and the parasitic elements, and you'll buy
Speaker 1: it based on front back ratio in the game that
Speaker 1: you need, going in the game that you are desired.
Speaker 1: Most shaggy designs have desirable radiation patterns also have a
Speaker 1: feed point impedance somewhere below fifty oms. With regular coacts
Speaker 1: with the feedpoint impedance from twenty to twenty five oms,
Speaker 1: this results in an undesirable SWR two to one. So
Speaker 1: the most common technique for matching the impedance is a
Speaker 1: gamma match. A gamma match is a shortened section of
Speaker 1: parallel conductor transmission line that uses the driven element as
Speaker 1: one of its conductors. Transmission line transforms the low impedance
Speaker 1: of the feed point to a higher value. An adjustable capacitor,
Speaker 1: either an actual variable capacitor or a shorter piece of
Speaker 1: insulated wire inside a hollow gamma rod is used to
Speaker 1: adjust the gamma match for s WR one to one.
Speaker 1: A mechanical advantage of the game a match over other
Speaker 1: techniques is that the driven element needed needs not to
Speaker 1: be insulated from the boom, which simplifies the construction. UH
Speaker 1: there's a beta match, which or sometimes reference as a hairpin,
Speaker 1: is a short length or stub a parallel conductor transmission
Speaker 1: line connected directly across the driven element feedpoint. The stub
Speaker 1: acts as an inductive reactants that can compensate for any
Speaker 1: capacity of reactants at the feedpoint. The balance is used
Speaker 1: to maintain the electrical balance between both halves of the
Speaker 1: driven element. Other techniques such as the Omega match and
Speaker 1: penis transformers and transmission line subs are also described, and
Speaker 1: you can read those in the ABRL handbook. Here's some
Speaker 1: practice questions. Which of the following describes an as methyl
Speaker 1: projection map? Okay, the map that shows the actual land
Speaker 1: mask says, wouldn't be that. It's going to be a
Speaker 1: map that shows the bearing distance for specific location. Okay,
Speaker 1: So that when you bind a yaggy antenna member, it's
Speaker 1: gonna it's gonna project and as anthyl projection in the
Speaker 1: in the four direction. Uh. Which of the following would
Speaker 1: increase the bandwidth of a yaggy and antenna larger diameter elements? Uh?
Speaker 1: The spacing is is uh is has will affect the
Speaker 1: gain and the impediance, but the lord of the element
Speaker 1: size actually helps with the band with the with with
Speaker 1: the bandwidth which is approximate link of the driven element
Speaker 1: of a yaggy antenna, that'd be a halfwave link. Remember
Speaker 1: it's a The driven element is a dipole, so it's
Speaker 1: half wave length. Uh. How do the lengths of the
Speaker 1: three element yaggy, reflector and director compared to that of
Speaker 1: the driven element? Uh, the reflector, let's see, the reflector
Speaker 1: is going to be longer. Director's gonna be short. Its
Speaker 1: like it's gonna be a here. Yeah, he's the answer.
Speaker 1: So the usually the so so the director's right behind
Speaker 1: the driven element, towards the back of the antenna, it's
Speaker 1: a little bit longer. And then in front of the
Speaker 1: driven element. What's the primary effect of increasing bloom lengths
Speaker 1: and adding directors to the and to the yaggy antenna?
Speaker 1: You're going to increase the game. Kay. What does front
Speaker 1: to back ratio mean in reference to a yaggy and
Speaker 1: it would be the uh power radiated in the major
Speaker 1: lobe compared to the opposite direction. Okay, So it's the
Speaker 1: ratio of how much power goes forward to that to
Speaker 1: the radio power forward versus the radio power in the back.
Speaker 1: What is meant by the main lobe of a director
Speaker 1: of a direct directive directional antenna? It's the direction of
Speaker 1: which the maximum field strength from the antenna is radiated.
Speaker 1: It's it's that is that direction. So the main lobe
Speaker 1: on a yaggy is usually on a yaggy is where
Speaker 1: is where the elements where the the antenna is pointing
Speaker 1: out to the front of the antenna. Which of the
Speaker 1: falling can be adjusted to optimize forward gain, front to
Speaker 1: back ratio or SWR bandwidth of a yaggy antenna, length
Speaker 1: of the boom, number of elements spacing all those things deep.
Speaker 1: What is a beta or hair painting or or hair
Speaker 1: pin match. It's a shorted transmission line stub place at
Speaker 1: the feet point of a yaggy antenna to provide impedance matching.
Speaker 1: So it's it's a way to remember the the yagy
Speaker 1: itself is about twenty five homes. He needs something to
Speaker 1: raise the impedance up. Its about fifty oms of your
Speaker 1: to to your system. And the beta or hair pin
Speaker 1: match is a transmission line stub that that that that
Speaker 1: does that transformation for you. Whatis is the fallowing is
Speaker 1: a characteristic of using a gamma match with a yaggy antenna.
Speaker 1: A Let's see, it does not require that the driven
Speaker 1: element be insulated from the boom. Our next section, we're
Speaker 1: going to talk about loop antennas, specialized antennas, and feed lines.
Speaker 1: So what's a loop antenna. It can be a circular, square, triangular,
Speaker 1: or any simple open shape that is not too narrow.
Speaker 1: Feed line can be attached at a break in the loop,
Speaker 1: or a small loop can be used to a couple
Speaker 1: RF energy to the main loop. Square loop with each
Speaker 1: leg a quarter of a wavelength long is called a
Speaker 1: quad loop. A triangle or delta loops are usually symmetrical,
Speaker 1: each leg a third of a wavelength long. A one
Speaker 1: wavelength loop acts electrically like two dipoles connected in the end,
Speaker 1: with the open ends brought together circumforts much larger than
Speaker 1: one wavelength. Typically a current patterns around loop have more
Speaker 1: than two peaks and knowles. This results in an essentially
Speaker 1: omni directional pattern, with the peak angle radiation somewhat lower
Speaker 1: than a dipole at the same height. There's quad and
Speaker 1: delta loop beams. Popular variation of the yaggy antenna uses
Speaker 1: what's called quad loops for elements. It's called a quad
Speaker 1: It has two or more full sized loops mounted on
Speaker 1: a boom. Quad or delta loop. Beam driven elements are
Speaker 1: approximately one wavelength in circumference and operate on the same
Speaker 1: principle of re radiation and face shift as does the yaggy.
Speaker 1: The driven element of a quad is about a quarter
Speaker 1: wavelength per side, and of a symmetrical delta loop about
Speaker 1: a third of a wavelength per side. Quad and delta
Speaker 1: loops reflectors are about five percent longer in circumference than
Speaker 1: the driven element, and the directors about five percent shorter.
Speaker 1: Front to back ratio is generally better for the yaggy.
Speaker 1: It's usually better for the yaggy. Right. Here's the figure.
Speaker 1: Here is showing a wavelength of the loop antennas. So
Speaker 1: this is your antennas. Here the square, and this is
Speaker 1: what the pattern looks like. The direction of maximum signal
Speaker 1: is broadside to the plane of the loop, whether round,
Speaker 1: quad or delta or orienting the loop vertically aims and
Speaker 1: maximum signal towards the horizon, which is good for deep
Speaker 1: which is good for DX. So full way of blue antenna.
Speaker 1: I've got a full wave blue antenna that I use
Speaker 1: one hundred and sixty meters. It's not up very high,
Speaker 1: so uh, but that's the high side that I could
Speaker 1: get it, but you know, one hundred and sixty countries later,
Speaker 1: I think I'm pretty happy with it right now. So
Speaker 1: talk about small loops. When the circumference of the loop
Speaker 1: becomes less than a third of a wavelength, the current
Speaker 1: in the loop becomes relatively uniform all the way around
Speaker 1: the top, which causes so small loops cause radiation patterns
Speaker 1: to develop sharpnols the broad side to the plane of
Speaker 1: the loop. Small loops in wide use. They're in wide
Speaker 1: use as receiving antennas and portable or low profile transmitting antennas.
Speaker 1: The sharpnel broad side to the loop makes them effective
Speaker 1: for direction finding. This is typically small loop. Now they
Speaker 1: have a very high Q. Sometimes they're difficult to tune.
Speaker 1: Some have an automatic tuner that comes with them, which
Speaker 1: is great, but they're very high Q. They're very high
Speaker 1: Q antennas halo antenna which is double bent into a
Speaker 1: circle or square called the squalow with the ends separated
Speaker 1: by a small gap. Not a continuous loop, but otherwise
Speaker 1: viewed as a half wave loop. Usually they're horizontally mounted
Speaker 1: horizontally so they produce an omnidirectional pattern, with the horizontal
Speaker 1: pattern preferred for VHF week signal operating halos for six
Speaker 1: and two meters can be mounted on a vehicle for
Speaker 1: mobile operations. Well, which direction is the maximum radiation from
Speaker 1: a VHF UHF halo antenna. That would be omnidirection in
Speaker 1: the plane of the of the halo. In which direction
Speaker 1: or or direction does in an electrically small loop less
Speaker 1: than one tenth of a wavelength. That's circumference. Have nols
Speaker 1: and his radiation patterns, and that's broadside to the loop.
Speaker 1: Talk about some random wire antennas. It's not practically always
Speaker 1: to have a half wave or a quarterwave long resident antenna.
Speaker 1: A random wire can be used instead, connected directly to
Speaker 1: the output of the transmitter or tuner without a feed line.
Speaker 1: This may result, however, you gotta be careful. Ray eight
Speaker 1: RADI eight random wire antennas may result in significant RF
Speaker 1: currents and vultures at the station equipment r F burns.
Speaker 1: They can give excellent results on any band for which
Speaker 1: the transmit or tuner can accept the feed point impedance.
Speaker 1: Typically got to have a tuner with these because they're
Speaker 1: not because they're not resonant. You can stack antennas stacking
Speaker 1: antennas vertically or horizontally results in more gain and more
Speaker 1: and as more and more directors are added, the beamwidth
Speaker 1: of the main lobe angle between points on the main lobe,
Speaker 1: which gain is three dB or less than maximum narrows.
Speaker 1: Vertically stacking antennas increases gain and narrows the elevation bandwidth.
Speaker 1: Both vertical stacks with the antenna directly above each other
Speaker 1: are spaced about half of a wavelength apart space half wavelength.
Speaker 1: Additional gain for vertical stack of two horizontally polarized beams
Speaker 1: is about three dB. You can double your power by
Speaker 1: adding another antenna on top. There's an example of of
Speaker 1: a horror of horizontally stacked and vert stacked. So stacked
Speaker 1: the antennas produces more gain in the main lobe, and
Speaker 1: two yaggis are stacked vertically at the same mass. So
Speaker 1: here's an example vertical stack horizontally stack. Another antenna called
Speaker 1: the log periodic antenna. TV antennas are often log periodics.
Speaker 1: Log refers to logarithmic and periodic means the spacing of
Speaker 1: the elements, which is referring to the spacing of the
Speaker 1: elements along the boom, the link and spacing of the
Speaker 1: elements increases. Logarithmic logged rhythmically from one end to the
Speaker 1: other's designed to have a constant radiation pattern in low
Speaker 1: s of R over a wide frequency bandwidth as much
Speaker 1: as ten to one, meaning the log periodic can be
Speaker 1: used over several bands. Not as much gain or front
Speaker 1: to back ratio as a yaggy antenna, but wide band
Speaker 1: multi band okay, and a log periodic antenna looks like this.
Speaker 1: It's the log pre dipole array consists of dipoles fed
Speaker 1: by common feed line that alternates polarity between elements. Traditional
Speaker 1: TV antennas sweep the elements slightly forward. Beverage antennas was
Speaker 1: invented by Harold Beverage. They're designed not to have high gain,
Speaker 1: but to reject noise and interfering signals that are not
Speaker 1: from the desired direction. Results in lower signal strength but
Speaker 1: a better signal to noise ratio to referred to as
Speaker 1: a traveling wave antenna, it consists of a long, low wire,
Speaker 1: usually less than twenty feet high, aligned with the preferred
Speaker 1: signal direction. They're used exclusively for direction receiving on MF
Speaker 1: and lower HF bands. Forty meters and longer wavelengths. It's
Speaker 1: high ground losses, and it has high ground losses and
Speaker 1: is too inefficient for use as a transmitting antenna. It's
Speaker 1: a great receive antenna, like I said, and it can
Speaker 1: it can improve your signal to noise radio ratio by
Speaker 1: rejecting some of the noise. Here's an example of the
Speaker 1: beverage antenna, usually one to quarter one to four times
Speaker 1: wavelengths easily kind of close to the ground. It has
Speaker 1: a terminating resistor. That's why it's not great for transmitting,
Speaker 1: because it's gonna absorb all your energy. But it's a
Speaker 1: great receipt antenna. And you can see by the pattern
Speaker 1: there it's it's got great rejection to the back. Okay,
Speaker 1: So signals arriving from the direction of the terminating resistor
Speaker 1: which is pointing towards the back and douce a traveling
Speaker 1: voltage wave along the wire. It gets transferred to the
Speaker 1: feed line and the feed points signals arriving from other
Speaker 1: directions or either broad side of the terminating resistor or
Speaker 1: do not induce voltage waves on the end on the
Speaker 1: and the antenna. So a lot of people use these
Speaker 1: for you know, a lot of your radios have a
Speaker 1: received antenna, and this is one. This is an example
Speaker 1: where where you want to hook that kind of of
Speaker 1: of of of antenna in. Okay talk about multi band antennas,
Speaker 1: but Hams generally mean by multi banded antenna is the
Speaker 1: design that reconfigures itself electrically for each band of operation.
Speaker 1: Those basic multi band antenna is a trapped dipole. Each
Speaker 1: trap is a parallel l C circuit. Resonance acts like
Speaker 1: an open circuit below residence like an adductor, and above
Speaker 1: like a capacity. And we we went through that and
Speaker 1: we talked about ls and sea circuits, tank circuits. At
Speaker 1: lower frequencies, the traps and inductance to the antenna make
Speaker 1: the antenna look electrically longer, and at higher frequency, the
Speaker 1: capacity of electrically shortens the end the the the antenna.
Speaker 1: Usually you'll see these on a bean antenna. It's got
Speaker 1: several traps, and these traps again make this the antenna
Speaker 1: think it's you know, sixty something feet long and it's
Speaker 1: really only twenty five feet long or something like that.
Speaker 1: So they're used quite a bit for bean antennas for
Speaker 1: H for H for HF because you practically couldn't put
Speaker 1: a big yaggy up at forty meters it'd be super long,
Speaker 1: heavy high. So these antennas work pretty good, pretty popular
Speaker 1: for the HF bands, and they worked very They worked
Speaker 1: very very well. Again, you got one antenna that operates
Speaker 1: over multi bands. Trapped diepoles is another one. The lowest
Speaker 1: frequency of operation of an antenna acts like a regular diepole.
Speaker 1: It can be shortened by the inductance of the trap.
Speaker 1: Yaggys can also use traps to work on several bands.
Speaker 1: Three element tri band yaggy with traps and the elements
Speaker 1: works well twenty fifteen and ten. So sort of like
Speaker 1: what we just looked on the previous chart that was
Speaker 1: a a yaggy with traps in it. Some drawbacks with
Speaker 1: traps because it works on multiple bands. It radiates harmonics
Speaker 1: and spurious signals also, and uh so you've got to
Speaker 1: make sure that you've uh that that you get that
Speaker 1: you've got your transmitter tune right and uh to watch
Speaker 1: your spur you signals. Traps lose losses reduced the efficiency
Speaker 1: of the of the of the antenna. They are coil
Speaker 1: and they will absorb some of your and your your
Speaker 1: your energy and they don't radio as well as a
Speaker 1: full sized antenna. But it's a it's a great compromise. Hey,
Speaker 1: what is the characteristics of a random wire HF antenna
Speaker 1: connected directly to the transmitter. Let's see it make cares
Speaker 1: magnificant RF current. That's a that's what you gotta be
Speaker 1: careful for. You gotta look out for because you're you
Speaker 1: can have highest of br on the thing and gotta
Speaker 1: be careful in free space? How does the gain of
Speaker 1: three element UH horizontally polarized jaggy antennas vertically space a
Speaker 1: half wave length apart typically compared to the gain of
Speaker 1: a single element. So, as we talked about, if you
Speaker 1: can stack two of them vertically, you get about a
Speaker 1: three d B gain should be b yep. What's the
Speaker 1: primary function of antenna traps and it's two to enable
Speaker 1: multiban operation. What is an advantage of vertical stacking of
Speaker 1: horizontal polarized yaggy antennas spig selection simultaneous? It narrows the
Speaker 1: main lobe in elevation, that's correct. Which of the following
Speaker 1: is an advantage of a log periodic and antenna h
Speaker 1: H it has wide band will bands? Okay, which of
Speaker 1: the following describes a log periodic antenna. Let's see element
Speaker 1: spacing very logged medically along the boom. That's correct. Game varies, sorry,
Speaker 1: so it had to be eight. Okay, the element spacing
Speaker 1: is logarithmically related. What is the primary use of a
Speaker 1: beverage antenna directional receiving antenna for a for HF bands.
Speaker 1: I think that's the right answer. Remember that's the one
Speaker 1: that's got to resist her in it, and it's not
Speaker 1: good for transmitting, but it's great for receiving, and it
Speaker 1: has uh some directional to it, which is the following
Speaker 1: is a disadvantage of multi band antennas must be used.
Speaker 1: It must be fed ah uh poor harmonic rejection because
Speaker 1: the resonant. So if I've got a twenty forty multi
Speaker 1: dipole and I'm on twenty meters, will I'm also generating
Speaker 1: a forty meter harmonic too, So you got to be
Speaker 1: character and him because that harmonic will be resident on
Speaker 1: one of your of your antennas. Okay, let's talk about
Speaker 1: feed lines and characteristic compedants. Bounce feed lines the system
Speaker 1: two parallel conductors separated by instantly material in the form
Speaker 1: of strips or spacers. They have different characteristic impedances that
Speaker 1: characterize how electromagnetic energy is carried by the feed line.
Speaker 1: For parallel conductor feed lines of radius of conductors and
Speaker 1: the distance between them is determined by the Z which
Speaker 1: is the impediance. Most common type is window line. Typical
Speaker 1: impedance for a window lines about four hundred and fifty ohms,
Speaker 1: some as low as four hundred most common character verst
Speaker 1: of coaxial feed lines UH fifty homes and seventy five homes.
Speaker 1: Here's an example of some of the different types of
Speaker 1: feed lines. This is UH. Yes. See here's a seventy
Speaker 1: five O twin lead four and fifty on window line.
Speaker 1: Coacts with different kinds of dielectric materials, different kinds of shielding.
Speaker 1: A lot of different UH types of coax shielding is
Speaker 1: available and insulting materials, and so you have to you
Speaker 1: have to UH pick the UH coax UH. If you're
Speaker 1: using coacts, you want to pick the get the impedance
Speaker 1: that you want, get the jacketing, get the shielding that
Speaker 1: you want, get the UH jacketing material that you need.
Speaker 1: If you're variant outside, it's going to be in sunlight.
Speaker 1: A lot of factors to consider. Themen picking at your
Speaker 1: coax and your and your feet in your feed lines.
Speaker 1: So right, so's talk about fording reflected power and SWR.
Speaker 1: Feed line transfers all of its power to the antenna
Speaker 1: when the antenna feed line are matched. If the impedances
Speaker 1: don't match, some of that power is reflected back and
Speaker 1: reflected by the antenna back towards the transmitter. So we
Speaker 1: have forward power, it's power traveling down towards the antenna
Speaker 1: and reflected power power that's reflected back. Power in a
Speaker 1: feed line is reflected at any point at which the
Speaker 1: impedance of the feed line changes, so that cannot necessarily
Speaker 1: be at the antenna, but could be at the connector.
Speaker 1: Or you've got an interface coming out of your shack
Speaker 1: to the out to the outside a patch panel. Whenever
Speaker 1: that feed line is interrupted or changes, the impedance can
Speaker 1: change through that and you can get a reflection there.
Speaker 1: SWR the waves carrying forward power and reflected power from
Speaker 1: stationary patterns inside the feed line. It's called SWR. It's
Speaker 1: is called standing waves. The ratio of the peak voltage
Speaker 1: in the standing wave to the minimum voltage is called
Speaker 1: the standing wave ratio. Standingwave ratio measures how well the
Speaker 1: antenna feed line and impedances are matched. One to one
Speaker 1: is a perfect match, none of the power is reflected.
Speaker 1: SWR of infinity in the case that all the power
Speaker 1: was reflected, and SWR is always greater than one to one.
Speaker 1: For example, you always say three to one, you won't
Speaker 1: say one to three. One to one's perfect, So there's
Speaker 1: never a perfect system, so always gonna be a little
Speaker 1: greater than one to one. So how do you calculate SWR?
Speaker 1: SBR is equal to the ratio of the high of
Speaker 1: the higher of antenna feed point impedance or feed line
Speaker 1: character's competence to the lower. So example, what is SWR
Speaker 1: in a fifty feed line connected to a two hundred load, Well,
Speaker 1: that would be two hundred divided box four, so i'd
Speaker 1: be four to one. What's the SWR and a fifty
Speaker 1: on feed line connected to a ten o load fifty
Speaker 1: divided by ten five to one? So remember you're always
Speaker 1: it's gonna be the ratio of the higher one to
Speaker 1: the lower one, right, So you're not going to get
Speaker 1: a number less than one. Okay. SWR can be measured
Speaker 1: anywhere along the feed line. However, However, it's most most
Speaker 1: commonly measured UH at the connector at the connection to
Speaker 1: the trend to the transmitter UH SWR measured by an
Speaker 1: SWR meter, also called the bridge. Transmitting equipment is designed
Speaker 1: to work at full power with an SBR at the
Speaker 1: input impedance feed line of about two to one or lower.
Speaker 1: Antennas that are much too short or too long will
Speaker 1: not work well. We'll have extreme feedpoint impedance causing high
Speaker 1: SWR matching feed line and the load. The antenna impedances
Speaker 1: eliminate standing waves from reflected power and maximize power delivered
Speaker 1: to the load, but not always practical. The impedance matching
Speaker 1: is more often done at the transmitter end of the
Speaker 1: feed line. Devices used to reduce SWR called impedance matchers.
Speaker 1: Transmatch antenna coupler and antenna tuner tuners do not tune
Speaker 1: the antenna at the amplifier thinks it's got a good
Speaker 1: match out there, so in other words, an antenna tuner
Speaker 1: increases the power transfer for the transmitter to the feed line.
Speaker 1: So if you've got a bad antenna, still a bad antenna,
Speaker 1: all right, So impedance matching. These are devices constructed from
Speaker 1: inductors and capacitors that are adjusted by the operator. A
Speaker 1: T circuit can match a wide variety of impedances at
Speaker 1: the feed line connection to fifty homes that matches trans
Speaker 1: output penians. It's important to remember that the SWR in
Speaker 1: the feed line between the impedance matching device and the
Speaker 1: antenna does not change The device just changes the load
Speaker 1: going to the transmitter SWR. The feed line stays the same, okay.
Speaker 1: So if you've got highest WR with your tuner, you've
Speaker 1: still got highest WR on the other side of the tuner, okay.
Speaker 1: But your transmitter is going to put transfer as much
Speaker 1: power as it can to the load. So a T
Speaker 1: network usually consists of two capacitors and in an inductor,
Speaker 1: and then there's a let's see the PI network okay,
Speaker 1: so installed at the transmitter into the feed line. A
Speaker 1: T network is designed to be used with unbalanced coaxial
Speaker 1: feed lines. This circuit uses two variable capacitors and one
Speaker 1: variable inductor. To use balanced feed lines such as window line.
Speaker 1: The output of a T network can be inductively coupled
Speaker 1: to the output, so that need either of the feed
Speaker 1: line conductors is connected to ground. Now, feed line losses
Speaker 1: feed line dissipates a lot of energy, disipates a little
Speaker 1: of the energy that's carried as heat, called attenuation or loss.
Speaker 1: Loss in the feed line is measured in DB's per
Speaker 1: unit of linked, usually specified as dB per hundred feet.
Speaker 1: The loss increases with frequency for all types of feed lines.
Speaker 1: The smaller the cable diameter, the higher the loss. Increasing
Speaker 1: SWR and a feed line also increases the total loss.
Speaker 1: The higher the feed line loss, the lower the measured
Speaker 1: SWR will be at the input to the line. A
Speaker 1: lot of people don't realize how much loss they have
Speaker 1: in their coax feed system. If you've got like we
Speaker 1: I think we had in our earlier talking about about
Speaker 1: dv A one dB loss is you're going to lose
Speaker 1: twenty percent of your power. So if you had one
Speaker 1: hundred watts with the one dB loss in your cable,
Speaker 1: put ad watts to the antenna and you that other
Speaker 1: twenty watts is dissipated as heat in the PAX feed line. Okay,
Speaker 1: so what's the purpose of an antenna tuner? Reduces the
Speaker 1: SWR to the feed line, reduces sw articipation increases power
Speaker 1: transfer from the transmitter to the feed line. It's going
Speaker 1: to be c You may want to think an antenna tuner.
Speaker 1: A lot of people say it reduces the SWR. Well,
Speaker 1: no it doesn't. The antenna and the SWR on the
Speaker 1: other side of the antennaituner. The SWR is still whatever
Speaker 1: it was before, you know. So it just makes the antenna.
Speaker 1: It makes sure antenna allows antenna to transfer as much
Speaker 1: power as it can to the feed line itself. Which
Speaker 1: are the following factors? Determines the characteristic impedance of a
Speaker 1: parallel conductor feed line? See the distance between them b
Speaker 1: A between the centers of the conductors and the radius
Speaker 1: of the conductors themselves. What is the relationship between high
Speaker 1: SWR and transmission line loss uh let's see yep. Highest
Speaker 1: WR increases loss in a lossy transmission line. What is
Speaker 1: the nominal characterist competence of window line transmission line? It's
Speaker 1: about four hundred and fifty oms. What causes reflected power
Speaker 1: at an antenna's feed point that'd be a difference in
Speaker 1: the feed point line impediancy antenna feed point line intendants
Speaker 1: uh an ten of feed pointing impedance, mismatch in impedance.
Speaker 1: How does the attenuation of quaxio cable change with increasing frequency. Okay,
Speaker 1: so the higher the frequency, the more loss you're going
Speaker 1: to have. So intend so the uh antena and is
Speaker 1: TENU increases, so it would be B. And what units
Speaker 1: is RF feed line loss usually expressed? It's usually in
Speaker 1: dB per hundred feet D. What must be done to
Speaker 1: prevent standing waves on a feed line connected to an antenna?
Speaker 1: Not a number, not B, C B D. Antenna feed
Speaker 1: point penis must be matched to the characteristic competence of
Speaker 1: the feed line. If the SWR on an antenna feed
Speaker 1: line is five to one and a matching network at
Speaker 1: the transmitter end of the feed line is adjusted to
Speaker 1: present an SWR one to one to the transmitter, what
Speaker 1: is resulting sw R of the feed line? And it
Speaker 1: would be five to one. So B what standyway ratio
Speaker 1: results from connecting a fifty oero feed line to a
Speaker 1: two hundred er resistant load will be two hundred divided
Speaker 1: by fifty to be four be four to one. What
Speaker 1: sanuay racial results from fifty on feed line to a
Speaker 1: ten ole resistant blode, this case will be fifty divided
Speaker 1: bout ten five to one. All right, now we're going
Speaker 1: to talk about the ionosphere. The sun and scatter modes.
Speaker 1: So the ion a sphere. Uh, it's what's called it's
Speaker 1: the upper reaches of the atmosphere. It gets thinner with distance.
Speaker 1: It begins about thirty miles above the earth. It's remaining
Speaker 1: gases thin, it's enough for ionization to occure. The region
Speaker 1: of the atmosphere becomes very it becomes a very weak conductor.
Speaker 1: And you can see here that it's actually three layers.
Speaker 1: There's a D layer closest to the earth about thirty
Speaker 1: miles up, the E layer, the F one, and the
Speaker 1: F two. The F one and the F two combined
Speaker 1: at night, so it's just one F region at night,
Speaker 1: and the D and E layer disappear at night. Okay,
Speaker 1: So related to the sun, all right. The D layer
Speaker 1: thirty sixty miles is only present when illuminated by the sun.
Speaker 1: It disappears at night because ions and tree electrons are
Speaker 1: close enough together to recombine quickly when no UV is present,
Speaker 1: returning it to a neutral condition. At night, the D
Speaker 1: and E regions disappear, and the F one and F
Speaker 1: two regions combined to form a single F region. Okay,
Speaker 1: So again, the ionosphere consists of several regions of ionized
Speaker 1: particles different heights above the earth. The E layer sixty
Speaker 1: to seventy miles above the earth acts similar to the
Speaker 1: D layer. It's higher and less dense than the D region,
Speaker 1: and it enables it to last a little bit longer
Speaker 1: after sunset. The F layer one hundred three hundred miles
Speaker 1: above is the least dense of the three layers, and
Speaker 1: it remains partially ionized at night. During the day, the
Speaker 1: F one region splits into F one and F two
Speaker 1: during at the height of the F region varies quite
Speaker 1: a bit with local time, season, latitude, and solar activity,
Speaker 1: so it changes based on those things. At any particular location,
Speaker 1: the stronger the illumination from the sun, the higher the
Speaker 1: F two layer will be, so it's maximum height is
Speaker 1: reached at noon, when the sun is overhead and the
Speaker 1: asphere refracts radio waves. It's a weak conductor. Refraction amount
Speaker 1: leads depends on the amount of ionization and wave frequency.
Speaker 1: The higher the ionization, the more the refraction. The lower
Speaker 1: the frequency, the more the refraction, so HF signals relatively
Speaker 1: good refraction are reflected back to the Earth's surface. VHF
Speaker 1: and UHF signals essentially have no refraction. Remember, frequency is
Speaker 1: related to what gets refracted okay VHF okay, So each reflection.
Speaker 1: Each reflection is called the hop and it allows signals
Speaker 1: to be reached hundreds or thousands of miles away. It's
Speaker 1: called skywave propagation via the ionosphere, so it's called skip.
Speaker 1: So skywave propagation via the iosphere is called skip. The
Speaker 1: E layer acts similar to the D layer oop. Sorry
Speaker 1: about that, went to my next chart. The higher the
Speaker 1: region from which the reflection takes place, the longer the hop.
Speaker 1: Waves reflected from F two layer travel at twenty five
Speaker 1: hundred miles before returning to the ground. Hops from the
Speaker 1: E layer a shorter, about twelve hundred miles, and some
Speaker 1: combinations of frequency and iization level result in weak bending.
Speaker 1: The wave must leave the Earth surface at a low
Speaker 1: enough angle for the binding of the wave to be
Speaker 1: sent back. Highest takeoff angle at which a wave can
Speaker 1: be returned to the Earth is called the critical angle.
Speaker 1: Critical angle depends on I spirit ionics, spirit conditions, and frequency.
Speaker 1: Radio waves are reflected and bent in the ion spere,
Speaker 1: so they return to Earth far from the transmitting station.
Speaker 1: Without refraction in the ionosphere, radio waves would pass directly
Speaker 1: into space. So I've got a station over here it's
Speaker 1: transmitting hits the ionosphere at the correct angle and reflected
Speaker 1: back to Earth, and a station on the other side
Speaker 1: of the Earth canton here. If the there's a critical angle,
Speaker 1: we'll talk about the critical angle over here. Waves that
Speaker 1: leads the transmitting antenna above the critical angle are refracted
Speaker 1: in the ionosphere, but not bent towards the return to
Speaker 1: the Earth. It's at and below the critical angle will
Speaker 1: return to Earth. The lowest angle return waves that return
Speaker 1: to the Earth at the greatest distance, which is why
Speaker 1: low angles of radiation are often best for d X stations.
Speaker 1: So depending on how your signal is, the angle of
Speaker 1: which it takes off from your station depends on does
Speaker 1: it get reflected reflected back or not so, and this
Speaker 1: is called the critical angle. Here, the critical angle the
Speaker 1: critical frequency is the highest frequency at which waves transmitted
Speaker 1: straight up will return to Earth. Okay, absorption uh. The
Speaker 1: enemy of propagation is absorption UH. In D and E regions,
Speaker 1: waves passing through the dense the denser gases are partially absorbed.
Speaker 1: The D region is not good is not very good
Speaker 1: at refraction and HF bands below ten megahertz a M
Speaker 1: broadcast bands and at lower frequencies the d region completely
Speaker 1: the absorbs radio waves during the day, preventing those waves
Speaker 1: from returning to Earth. Absorption increases in daytime and when
Speaker 1: solar UV is more intense. When is the best time
Speaker 1: to transmit on HF below ten megaherbs, It's gonna be
Speaker 1: at night and AM radio stations. That's why they can
Speaker 1: run the high power during the day, and when the
Speaker 1: sun goes down they have to reduce their power because
Speaker 1: during the day all their energy is getting absorbed, so
Speaker 1: it's not going other than locally. But at night it
Speaker 1: would it would bounce off the f layer and would
Speaker 1: be it would be a big problem. Noise Noise is
Speaker 1: another enemy of propagation. It covers up weak signals, stronger
Speaker 1: at frequencies below VHF. Lower you go in frequency, the
Speaker 1: stronger the noise or static. It varies seasonally, most noticeably
Speaker 1: on lower frequ the hsvams in the summer, when atmospheric
Speaker 1: noise is the strongest I know around here. In the afternoons,
Speaker 1: a lot of thunderstorms around the area across the state,
Speaker 1: and staticky long path and short path when iyosphere a
Speaker 1: long short path does not support propagation. Sometimes long path
Speaker 1: will occasionally propagation over long and short paths will be
Speaker 1: supported at the same time. Unless the paths are almost equal,
Speaker 1: there will be an echo or delayed. Signal arrives a
Speaker 1: fraction of a second later. In my experience, I've done
Speaker 1: this a couple of times. I've heard my signal go
Speaker 1: short and long path and there is a little echo delay.
Speaker 1: It's a cool thing that happens, and you get all
Speaker 1: excited about it. But it's a pretty cool. It's amazing
Speaker 1: phenomena around the world propagation. You can hear your own
Speaker 1: signal coming all the way around your location about one
Speaker 1: seventh of a second later, So conditions are right. It's
Speaker 1: a pretty cool thing. And this catch shows the Earth
Speaker 1: both has both great circle paths drawn between the two stations.
Speaker 1: So here I've got this is your station, and you
Speaker 1: transmit and it goes all the way around the Earth
Speaker 1: and comes to that station or short path is here,
Speaker 1: this is long path, and this would be short path
Speaker 1: this way, And like I said, sometimes I can hear
Speaker 1: you can hear your signal come all the way back around.
Speaker 1: Kind of cool. Okay, how is a directional antenna pointed
Speaker 1: when making a long path contact with that other station,
Speaker 1: it would be one hundred eight degrees from the station's
Speaker 1: short path. See like, if I'm trying to go here
Speaker 1: to Texas, I point towards the I guess towards the west.
Speaker 1: If I'm trying to for a short path for long paths,
Speaker 1: I point towards the east. If I can come all
Speaker 1: the way back around. What is a characteristic of skywave
Speaker 1: signals arriving at your location by both short path and
Speaker 1: long path. Let's see periodic feeling its light echo might
Speaker 1: be heard d. What is the approximate maximum distance along
Speaker 1: the Earth's surface normally covered on one hop using the
Speaker 1: F two layer, It's about twenty five hundred miles C.
Speaker 1: What is the approximate link distance of the Earth's surface
Speaker 1: normally for one hop using the E region, It's about
Speaker 1: twelve hundred D. What ion expirent region is closest to
Speaker 1: the Earth's surface That would be the D region. Ay,
Speaker 1: what is meant by the term critical frequency out of
Speaker 1: given incident angle highest frequency which is reflected back to Earth?
Speaker 1: That is the answer? Hey, why is skip propagation via
Speaker 1: the F two region longer than via the other I
Speaker 1: experienced regions densis highest because it's the highest c's the
Speaker 1: F two layer is the highest layer that we have
Speaker 1: is the furthest away. So what does the term critical
Speaker 1: angle mean as applied to radio wave propagation paths? It
Speaker 1: would be d the highest takeoff angle that will turn
Speaker 1: the radio wave to Earth under specific ionospirit conditions. There
Speaker 1: websites you can go to during the day that give
Speaker 1: you critical angle and frequency and changes of course as
Speaker 1: the sun changes, as there are places you can go
Speaker 1: look at the propagation. Why is a long distance communication
Speaker 1: on forty sixty eighty and one hundred and sixty years
Speaker 1: more difficult during the day. That's because it gets absorbed
Speaker 1: by the D region c O, which ionic sphirit region
Speaker 1: is the most absorbent of signal levels below ten megahertz
Speaker 1: during daylight hours. That would be the D region. Okay,
Speaker 1: sunspots and sun cycle, let's talk about the sun. I
Speaker 1: Hones sphere is dependent on solar UV to separate electrons
Speaker 1: from atoms. Much of the variation in UV radiation is
Speaker 1: due to sunspot activity. One complete sunspot cycle lasts about
Speaker 1: eleven years, when more sunspots are observed more UV is
Speaker 1: being generated, creating more intense ionization, improving propagation on higher
Speaker 1: frequency bands above ten megahertz and even into the lower
Speaker 1: VHF region. Here's a graph that shows the sunspot cycles
Speaker 1: over time, and E said, it's about eleven year cycle.
Speaker 1: We've just come off. I guess our peak cycle, and
Speaker 1: it's been it's been fund in mid twenty twenty three
Speaker 1: when this book was published, cycle twenty five was heating
Speaker 1: up and propagation on ten years and other bands was
Speaker 1: increasing at peak cycle. There may be sufficient solar UV
Speaker 1: to cause higher frequency bands ten meters, for example, to
Speaker 1: stay open for long distances during contacts at night. High
Speaker 1: ionization negatively impacts low frequency bands age sixty meters because
Speaker 1: it increases absorption when solar activity is low. Lower HF
Speaker 1: bands have good propagation, and higher HF bands above twenty
Speaker 1: megaherts fifteen meters and up often are often closed. One
Speaker 1: band that seems to do well at all times and
Speaker 1: sunspot cycles is twenty meters fourteen megaherts. It supports daytime
Speaker 1: communication worldwide nearly every day, and that's true twenty meters
Speaker 1: you can always almost always find something going on twenty
Speaker 1: meters seems to be the sweet spot. And here's a
Speaker 1: chart showing the propagation on the different bands. What happens
Speaker 1: during the day, what happens during nighttime. So the bands
Speaker 1: I mean dear deer during the day, the low the
Speaker 1: low bands are fairly quiet. You can do regional communications
Speaker 1: in the state of Alabama. We can talk regionally. Uh,
Speaker 1: when we're doing our areas activities during the day, we
Speaker 1: can can usually community we can communicate. So based on
Speaker 1: the time of day and the band you're on. And
Speaker 1: once you get your general license and start getting to
Speaker 1: the operate on the HF bande, you're gonna learn all
Speaker 1: these things here. You're gonna experience them. You're going to
Speaker 1: become an expert on propagation, when to when to communicate, where,
Speaker 1: what bands are good. It's a whole lot of fun. Okay.
Speaker 1: Sun spot's also seem to move across the Sun's surface
Speaker 1: because the Sun rotates once every twenty eight days. That
Speaker 1: is why propagation conditions good and bad on the HF
Speaker 1: bands often repeat themselves in a twenty eight day cycle
Speaker 1: as sunspots rotate back into the From Earth. Measuring the
Speaker 1: solar activity, you can there's a you can measure the
Speaker 1: number of suns of sunspots. There's a thing called the
Speaker 1: solar flux index. It describes the amount of twenty eight
Speaker 1: hundred megahertz radio energy. High levels indicate high solar activity
Speaker 1: and better HF propagation of O ten megahertz. A thing
Speaker 1: called the K index has a value from zero to nine.
Speaker 1: It represents the short term stability of the Earth's magnetic
Speaker 1: or geomagnetic field. Higher values indicate geomagnetic field is disturbed,
Speaker 1: which disrupts HF. An a index gives a good picture
Speaker 1: of long term geomagnetic field stability, and it ranges from
Speaker 1: zero stable to four hundred greatly disturbed. It's calculated from
Speaker 1: the K index. And there are sites you can go
Speaker 1: to that have this informational real time And so LOO
Speaker 1: activity is so important to propagation and communication that is
Speaker 1: monitored constantly. And like I said, you can go to
Speaker 1: certain websites and get these values and the information on
Speaker 1: the sun. Okay, So, how does a higher sunspot number
Speaker 1: affect h of propagation and answers? A higher sunspot number
Speaker 1: generally indicate a greater probability of good propagation at higher frequencies.
Speaker 1: Which is the following are least reliable for long distance
Speaker 1: communications during periods of lower solar activity. That would be
Speaker 1: fifteen meters, twelve and ten. That's what we've got, So
Speaker 1: we've got low solar activity higher bands. What is the
Speaker 1: solar flux index? It is the measure of the solar
Speaker 1: radiation at the ten point one seven centimeter wavelength band.
Speaker 1: At what point is the solar cycle? Does the twenty
Speaker 1: meter ban usually support or worldwide propagation during daylight hours?
Speaker 1: Usually it's all the time. D It's truly not affect.
Speaker 1: I mean, it's effective, but it usually does fairly well.
Speaker 1: Twenty meters of the place you can usually go to
Speaker 1: and find some activity no matter what time of day.
Speaker 1: What causens HF propagation conditions are very periodically at a
Speaker 1: twenty six to twenty eight day cycle, and that would
Speaker 1: be the rotation of the Sun's surface layers around its axis. C.
Speaker 1: What does the K index measure? It measures the short
Speaker 1: term stability of the Earth's magnetic field. What does the
Speaker 1: ax A index measures? And it's the long term stability
Speaker 1: of the Earth's geomagnet field. Which of the following is
Speaker 1: typical of the lower hf frequencies during the summer, let's
Speaker 1: see high levels of atmospheric noise and static I think
Speaker 1: that that is correct. Okay, so let's let's talk about
Speaker 1: propagation some terms. There's a maximum usable frequency called MUFF.
Speaker 1: It's the highest frequency of which propagation exists between two points.
Speaker 1: The lowest usable frequency l UF. Waves below the LUF
Speaker 1: will be completely absorbed by the ionis frequent by the ionosphere.
Speaker 1: MUFF and LUFF depend on specific data between two points, locations,
Speaker 1: and distance apart. It varies with the time of day,
Speaker 1: seasonal amount of solar radiation, and ionosphere stability. Operating near
Speaker 1: the maximum usual frequency often gives excellent results. Absorption is
Speaker 1: lowest just below it, one may One way to check
Speaker 1: actual conditions is to listen for propagation beacons. Some provide
Speaker 1: real time propagation information. Many stations between twenty eight point
Speaker 1: one nine and twenty eight point two five megahertz that
Speaker 1: are excellent are excellent sources of information about ten meter propagation.
Speaker 1: To make contact with the distance station, you will have
Speaker 1: to use a frequency between LUF and MUF, so the
Speaker 1: wave has been back toward the Earth but isn't absorbed
Speaker 1: if the MUF drops below the LUF, then no propagation
Speaker 1: exists between those two points via ordinary skywave. And there's
Speaker 1: on the on the web you can go find maps
Speaker 1: of the world that show the muff and the luff
Speaker 1: and it's got what the propagation is between different points
Speaker 1: on the Earth and the bands that are open, and
Speaker 1: a lot of good information out there. Okase talk about
Speaker 1: solar disturbances. Approximately eight minutes after a solar flare occurs
Speaker 1: on the Sun, the ultraviolet and X ray radiation released
Speaker 1: by the flare reaches the Earth. This radiation causes increased
Speaker 1: ionization and radio wave absorption in the d region. A
Speaker 1: solar flare, which is a large eruption of energy and
Speaker 1: solar mature. When magnetic field disruptions occur on the surface
Speaker 1: of the of a solar flare, there is a large
Speaker 1: eruption of energy and solar material when magnetic field disruptions
Speaker 1: occur on the surface of the Sun. A coronal hole,
Speaker 1: which is a weak area in the Sun's corona the
Speaker 1: outer layer through which plasma, ionized gas, and charged particles
Speaker 1: escape the Sun's magnetic field and streams away into space
Speaker 1: at high velocities. A coronal mass ejection CME is an
Speaker 1: ejection of large amounts of material from the corona, and
Speaker 1: all of these disrupt HF propagation some sudden ionosphere disturbances
Speaker 1: UV and X ray radiation from a solar flare travels
Speaker 1: at the speed of light to impact the ionosphere about
Speaker 1: eight minutes later. When radiation hits the ionosphere, the level
Speaker 1: of ionization increases rapidly, particularly in the D region. This
Speaker 1: increases absorption from causing a sudden ionospheric disturbance, also known
Speaker 1: as a radio blackout. Lower bands are more strongly affected,
Speaker 1: but communication may still be possible on a higher band.
Speaker 1: Sudden anospheric disturbances affect only the sunlit side of the Earth.
Speaker 1: The dark side communications may be relatively unaffected. Geomagnetic disturbances.
Speaker 1: This is the interaction between solar wind and geomagnetic field,
Speaker 1: which creates a region of space called the magnetosphere. Charged
Speaker 1: particles from coronal poles and coronal mass ejections travel considerably
Speaker 1: slower and take longer to reach the Earth about fifteen
Speaker 1: to forty hours. These particles deposit their energy into Earth's
Speaker 1: geomagnetic field and increase ionization in the E region, causing
Speaker 1: oral displays and creating a geomagnetic storm, which affects higher
Speaker 1: HF bands. First, long distance pass that traverse high latitudes,
Speaker 1: particularly those that pass near the magnetic poles, may be
Speaker 1: completely wiped out for days, for hours or days, and
Speaker 1: these can create auroras that reflect radio waves above twenty megahertz.
Speaker 1: Auroral propagation is strongest on six meters and two meters,
Speaker 1: modulating the signals with the hiss or buzz, so sometimes
Speaker 1: you can actually hear it on the signals. There's a
Speaker 1: modulation that happens. It's kind of cool effect. So here's
Speaker 1: some questions. What effect does a sudden honest spirit disturbance
Speaker 1: have on the daytime iono spirit propagation b It disrupts
Speaker 1: signals on low frequencies more than those on higher frequencies. Approximately,
Speaker 1: how long does it take for increase ultra ultra violet
Speaker 1: X radiation from solar flares to reflect radio propagation on Earth?
Speaker 1: About eight minutes? And what is a geomagnetic storm. It's
Speaker 1: a temporary disturbance in the Earth's geomagnetic field that bed
Speaker 1: How can a geomagnetic storm affect HF propagation It degrades
Speaker 1: high latitude HF propagation. How can geomagnetic activity benefit radio
Speaker 1: communications by creating a roar as that can reflect VHF signals.
Speaker 1: How long does it take a coronal mass ejection to
Speaker 1: affect radiopropagation on Earth? Usually it's about fourteen hours to
Speaker 1: several days. It just depends. How is long distance radio
Speaker 1: communication usually affected by the charged particles that reach Earth
Speaker 1: from solar chronal holes HF communication is disturbed? What factors
Speaker 1: affect the muff? Just a maximum usable frequency, path distance,
Speaker 1: time of day, solar ardiation, all of those affected. Maximum
Speaker 1: usual frequency is which frequency will have at least have
Speaker 1: the least attenuation For long distance skip propagation, that would
Speaker 1: be just below the maximum usable frequency. Once of the
Speaker 1: following is a way to determine current propagation on a
Speaker 1: desired ban from your station. Use a network of automated
Speaker 1: receiving stations on the Internet to see where your transmissions
Speaker 1: are and being received, because it's different all over the
Speaker 1: worth all over the world given at a given time,
Speaker 1: So check a network and see what the see what's
Speaker 1: the receiving stations showing at a particularly given time. How
Speaker 1: does say honest sphere effect radio waves with frequencies below
Speaker 1: them up and above their gluffs. Yeah, they are refracted
Speaker 1: back to Earth. What usually happens to radio waves with
Speaker 1: frequencies below the LUF They are attenuated before reaching the
Speaker 1: destination so to get through. What does LOUFF stand for?
Speaker 1: It's the lowest usable frequency for communication between two specific points. Okay,
Speaker 1: What does MUFF stand for? It's the maximum usable frequency
Speaker 1: between two points, right? And what does what happens to
Speaker 1: HF propagation when the luff exceeds the muff? Propagation is
Speaker 1: not possible over that path? That's correct, all right? Talk
Speaker 1: about some scatter modes, some terms called backscatter, that's reflections
Speaker 1: from the from from features on the Earth's surface. Waves
Speaker 1: can also be scattered from within the IONO sphere, allowing
Speaker 1: signals to be heard from stations too distant to be
Speaker 1: heard by ground wave and on on frequencies too high
Speaker 1: for short for short hop skywave propagation, scatter and backscatter
Speaker 1: helped fill in the skip zone where signals would otherwise
Speaker 1: not be heard. Signals received via HF scatter are usually
Speaker 1: weaker than those received by normal skyway propagation. Reflection is
Speaker 1: not very efficient and tends to spread out the signal.
Speaker 1: Such such signals sound disturbed, sound storted, resulting in fluttering
Speaker 1: or wavering. I'm striking the ground. After ionosphere reflection, radio
Speaker 1: waves may be reflected back towards the transmitting station. Backscatter
Speaker 1: consists of signals reflected by the ground back into the
Speaker 1: skip zone. Backscatter supports communication between stations that would otherwise
Speaker 1: be in each other's be in each other's skip zone.
Speaker 1: So I've got a signal, I've got a h I've
Speaker 1: got a station transmitting here, and I've got another receiving station.
Speaker 1: He's out of my skip zone. But because of some backscatter,
Speaker 1: some of that is actually received by this particular station.
Speaker 1: So the skip distance he's too far, he's out of
Speaker 1: my skip zone. But scattered signals from the ionosphere, he
Speaker 1: can sometimes hear me. And usually those are weak signals
Speaker 1: and they're fluttery, but he can. That's a that's a
Speaker 1: way he can. He can. I can communicate it near
Speaker 1: vertical incident skywave in VIZ. We just talked about what's
Speaker 1: the INVIS, what what are How we can build an
Speaker 1: VIZ and invis antenna for signal below the critical frequency
Speaker 1: the ionosphere reflects waves arriving at the angle even vertical
Speaker 1: always above five megahertz up to forty meters in VIZ
Speaker 1: is for a signal below the critical frequency when it
Speaker 1: when it is radiated vertically, the reflected scatters the signal
Speaker 1: back to Earth through the region of up to two
Speaker 1: hundred to three hundred miles. To make use of INVIZ,
Speaker 1: horizontally polarized dipoles are placed low to the ground so
Speaker 1: that the radiation pattern is almost omnidirectional and concentrated at
Speaker 1: high elevation angles near vertical incident skywave INVEZ communication and
Speaker 1: relies on signals below the critical frequency transmitted at high
Speaker 1: vertical angles. The signals are reflected by the aosphere back
Speaker 1: to Earth in the region around the transmitter. So here's
Speaker 1: an example. I've got a transmitting station here. I've got
Speaker 1: a guy on the other side of this mountain. I
Speaker 1: can't talk to him directly, but I can bounce the
Speaker 1: signal off the iosphere and get to him. And you're
Speaker 1: using the F layer to do this. H transmit this
Speaker 1: these reflections. Hey, what's the effect of HF scattered? So
Speaker 1: was the characteristic of HF scattered? Uh? They have a
Speaker 1: fluttery sound. Uh, usually weaker signals. What makes HF scatter
Speaker 1: signals often sound distorted? It's because there it's it's scattered
Speaker 1: to the zip code, the zip zone along several paths. Okay,
Speaker 1: Why are HF scattered signals in the skip zone usually weak?
Speaker 1: That's because only a small part of the signal is
Speaker 1: scattered back into the skip zone. What type of propagation
Speaker 1: allows signals to be heard in the transmitting station skip
Speaker 1: zone that would be scattered? What is a near vertical
Speaker 1: incident skywave propagation and that is short distance MF or
Speaker 1: HF propagation using high elevation angles. Okay, our next section,
Speaker 1: we're going to talk about electrical safety, RF exposure and
Speaker 1: outdoor safety. So, first of all, talking about electrical safety,
Speaker 1: preventing electrical shock. Always have a master on off switch
Speaker 1: for station and workbench, clearly labeled and somewhat away from
Speaker 1: the equipment. Don't put yourself in a position to be
Speaker 1: shocked when working inside equipment, Remove insulate or secure loose
Speaker 1: wires and cables, and use a ground stick to remove
Speaker 1: charge from capacitors. So, I see, what's a groundstick? Well, yeah,
Speaker 1: here we go. Here's a ground stick ground stick is
Speaker 1: a ground stick. It's touched to all circuitry inside an
Speaker 1: enclosure to ensure that that no high voltage is present.
Speaker 1: The alligator clip is attached to an electrical ground and
Speaker 1: the eyebolt sput on a on a contact with the
Speaker 1: circuit So you've got an insulating piece of PBC pipe
Speaker 1: and this allows you to touch certain components and discharge
Speaker 1: them to the potential of the gap itself. So what's
Speaker 1: the effects of electrical current through the human body on
Speaker 1: an average person? Well below a millionamp generally you can't
Speaker 1: perceive it. One million amp bank tingle, five million amps
Speaker 1: slight shock six to twenty five million ams painful for women,
Speaker 1: nine to thirty painful for men. Just the freezing you
Speaker 1: can't let that SIT's in the let go range fifty
Speaker 1: one hundred and fifty million amps very painful, and this
Speaker 1: is if you had contact. You know, inside the body,
Speaker 1: your skin is a resistance, so that helps, but it
Speaker 1: can be very painful. So it doesn't take much current
Speaker 1: to cause problems with the human body. Solder in safety
Speaker 1: so primarily solder is primarily lead based. Ten is added
Speaker 1: to lower the melting point. Lead is a known toxin.
Speaker 1: Always solder in a well ventilated area. Rosin flux smoke
Speaker 1: is likely not good for you in high doses. Use
Speaker 1: a well ventilated area if you can. When finished, wash
Speaker 1: your hands, remove solder or flux residue. As of two
Speaker 1: thousand and six, environmental regulations were passed for solder to
Speaker 1: eventually be lead free. Leaded soft are still available. Lead
Speaker 1: free sawder melts at significantly higher temperatures than traditional sixty
Speaker 1: to forty solder. Greater risk of damage to heat sensitive
Speaker 1: components because you got to you've got to run a
Speaker 1: little higher temperature. So what's the following is a danger
Speaker 1: for lead tin solder. Lead tin can contaminate food in
Speaker 1: your hands. Carefully, Hey, carefully, you know, wash your hands
Speaker 1: after you've handled lead tin solder. Okay, Wiring practices National
Speaker 1: Electrical Code Handbook contains the details for handling AC wiring
Speaker 1: and the home in the station. Use your local building
Speaker 1: codes ensure that home is properly wired to meet special
Speaker 1: local conditions. You standard wire color conventions. Hot which is
Speaker 1: red or black insulation it's connected to the brass terminal,
Speaker 1: or screw neutral, which is white insulation is connected to
Speaker 1: the silver terminal. Or screw, and green your ground. Ground
Speaker 1: is your green insulation or bare wires connected to the
Speaker 1: green or bear terminal screw. So those are the standard
Speaker 1: wiring AC wiring conventions use in your home. Don't run
Speaker 1: antenna feed lines overpower lines or service drops from a
Speaker 1: transformer to the house. Here's some standard wiring conventions. Standard
Speaker 1: wiring for outlets, one hundred and twenty and two hundred
Speaker 1: old AC plugs and receptacles. It's crrectally important to follow
Speaker 1: the correct wiring techniques for AC wiring. The white wires
Speaker 1: neutral green wire is ground, and the red or black
Speaker 1: wire is the hot lead. Note that two hundred and
Speaker 1: forty volt circuits may have two hot wires and the ground,
Speaker 1: so be careful when you wiring things are hooking things up,
Speaker 1: observe the wire colors and the correct connections. AC wiring
Speaker 1: most common sizes are number twelve gauge for twenty amp
Speaker 1: circuits and fourteen gauge for fifteen amp circuits. Use fuse
Speaker 1: or circuit breakers for the hot conductor for one hundred
Speaker 1: and twenty bolt circuits on both hot and use them
Speaker 1: on both for the hot conductors. On a two hundred
Speaker 1: and forty bolt circuit which uses the three or four wires.
Speaker 1: All right, here's the here's some current capacity ratings for
Speaker 1: some common wire sizes. The rating of a wire to
Speaker 1: carry current is called this opacity. When you are finished
Speaker 1: wiring the job, verify that you have the connect correct
Speaker 1: connections by using an AC circuit tester. So make sure
Speaker 1: you follow the right proper wiring sizes for the right conductors,
Speaker 1: all right. Fuses and circuit breakers are used to interrupt
Speaker 1: excessive current flow. Fuses do so by melting a short
Speaker 1: length of metal. Circuit breakers act like a fuse, but
Speaker 1: trip when current overloads occur. Always use properly sized fuses
Speaker 1: and circuit breakers. When installing fuses or circuit breakers in
Speaker 1: an AC circuit, be sure to replace them only with
Speaker 1: the correct ones, never in the in the correct lines,
Speaker 1: never in the neutral or ground lines. Be sure there's
Speaker 1: a fuse or circuit breaker in the hot conductor for
Speaker 1: one hundred and twenty bolt circuits and both conductors for
Speaker 1: two hundred and forty bolt circuit round fault interrupted circuit
Speaker 1: breakers are used in AC power circuits to prevent electrical
Speaker 1: shock trips. It trips if unbalanced is since in currents
Speaker 1: carried by the hot and neutral conductors. Sensitivity is just
Speaker 1: a few million amps of a balance between the hot
Speaker 1: and neutral, well below the threshold for electrical injury safety interlocks.
Speaker 1: This is a switch that prevents dangerous voltages or intense
Speaker 1: RF from being present when a cabinet or enclosure is open.
Speaker 1: You'll see these a lot if you have a high
Speaker 1: power amplifier, especially two amplifiers. When you take the top off,
Speaker 1: there's usually a switch that disables all the voltages. So
Speaker 1: if you're working on it and you know if you've
Speaker 1: got to bypass that, be real careful, all right. Several
Speaker 1: types physically disconnect high voltage RF when activated. Those are
Speaker 1: the switches I was just talking about. Usually take the
Speaker 1: chassis apart. There's usually a little rocker switch or some
Speaker 1: kind of switch in there that senses that shorts or
Speaker 1: ground high bolted circuits when activated, possibly blowing a circuit
Speaker 1: breaker or fuse, and the power supplies. Which wire wires
Speaker 1: in a four conductor to forty vowl AC circuit should
Speaker 1: be attached to fuses or circuit breakers? Okay, only the
Speaker 1: hot wires A you should not fuse The ground or
Speaker 1: circuit should not fuse The ground wires according to the
Speaker 1: Natural Electric Safety Code. What is the minimum wire size
Speaker 1: that may be used safely for it twenty amp circuit?
Speaker 1: That would be the twelve gate wire. What size a
Speaker 1: fuse or circuit breaker would be appropriate to use a
Speaker 1: circuit that uses a twenty A fourteen gauge wire. That
Speaker 1: would be the fifteen amp circuit breaker. Which of the
Speaker 1: following conditions may cause a ground false circuit interrupted? To
Speaker 1: disconnect AC power current flowing and one or more of
Speaker 1: the hot wires and the neutral or the hot wires
Speaker 1: to ground over voltage of the wires. It would be
Speaker 1: current flowing from one or more of the hot wires
Speaker 1: directly to the ground. B Which of the following is
Speaker 1: covered by the National Electric Code? That would be the
Speaker 1: electrical safety of the station. What is the purpose of
Speaker 1: a power supply interlock? Let's see it would be to
Speaker 1: ensure dangerous voltage or mirder moved from the cabinet when
Speaker 1: it's opened. That would be c okay. Some generals, some
Speaker 1: generator safety, fueling and ventilation problems cause more injuries associated
Speaker 1: with generators than from any other cause. Install generators outdoors,
Speaker 1: use them outdoors, Carbon monoxide and exhaust and quickly build
Speaker 1: up to toxic levels. We're using generators regularly. Installs carbon
Speaker 1: diox carbon monoxide detector alarms in living and working areas.
Speaker 1: Generator output connected directly to the homes. Wiring system must
Speaker 1: have the ability to disconnect power service from utility lines.
Speaker 1: Generators should always be shut off when refueling to avoid
Speaker 1: igniting fumes or splashing liquids from the spark flobe. A
Speaker 1: fire extinguishers should be kept near the generator and separated
Speaker 1: from the fuel. Here's some practice questions. Which of the
Speaker 1: following is true of an emergency generator installation. Generator should
Speaker 1: be operating, well operated and it's insulated from ground. It
Speaker 1: would be a should be operated in a well ventilated area.
Speaker 1: Lighting lightning goals of lightning protection. You should provide fire
Speaker 1: prevention for your home. It should it reduces or prevents
Speaker 1: electrical damage to your equipment. Use metal heavy use metal
Speaker 1: entry panels where signal control cables entered the house. Panels
Speaker 1: should be grounded nearby with a heavy metal strap. Ground
Speaker 1: rod must be bonded to the AC service entry ground
Speaker 1: rod outside the building with the heavy conductor and lightning
Speaker 1: arrestors should be installed at the entry panel where the
Speaker 1: feed line enters grounding wires and straps should be as
Speaker 1: short and directly and direct as possible. Do not use
Speaker 1: solder or to make ground connect ground connections. Solder joints
Speaker 1: could melt if hit by lightning size current. Use medical clamps,
Speaker 1: braising or whaling so you know. Never use a solder
Speaker 1: connection for your Whever you use solder to make ground connections,
Speaker 1: where you can have lightning compete, All towers, mass and
Speaker 1: antennas should be grounded. What should Why should solder joints
Speaker 1: not be used in lightning protections because a solder lightning
Speaker 1: will likely be destroyed by the heat of lightning. A.
Speaker 1: Where should the station's lighting lightning protection ground system be located?
Speaker 1: It should be outside the building of force. Which of
Speaker 1: the following is required for lightning protection? Ground rods lightning
Speaker 1: al must be connected d They all must be bombed
Speaker 1: together with all other grounds. Where should lightning arrestors be located?
Speaker 1: Where where it enters the building? They are exposure at
Speaker 1: high power levels. For some frequencies, the amount of energy
Speaker 1: that the body absorbs can be a problem. The maximum
Speaker 1: permissible expose your MPE is maximum intensity is the maximum
Speaker 1: intensity of r radiation to which a human being can
Speaker 1: be maybe exposed. Factor to consider when estimating MPE, that is,
Speaker 1: transmitter power level, density, frequency, average exposure time, and duty
Speaker 1: cycle of the transmission. Power density and frequency are primary ones.
Speaker 1: Those are things that you should think about. How much
Speaker 1: power you putting out? What's your frequency? What's your exposure time?
Speaker 1: In the duty sizet. Stations with a time average transmission
Speaker 1: of more than one milli a lot are subject to
Speaker 1: the FCC's ARF exposure rules. If your station exceeds the
Speaker 1: exemption criteria, you will need to evaluate it and according
Speaker 1: to the FCC OEt bulletin sixty five, So what does
Speaker 1: that mean? So talk about that in a minute. Power
Speaker 1: density is heating from exposure to RF signals caused by
Speaker 1: the body tissue absorption of r F energy, measured in
Speaker 1: milliwats per centimeter squared. R F field strings can also
Speaker 1: be measured in volts per meter and amps frem or
Speaker 1: milliwatts centimeter squared is the most useful for amateur requirements.
Speaker 1: Power density is highest near antennas and in the directions
Speaker 1: of which antennas have the highest gain, decreasing transmitter to
Speaker 1: power and increasing distance from the antenna lowers power density
Speaker 1: and vice versa absorption and limits SAR, which is specific
Speaker 1: absorption rate. This is the rate at which energy is
Speaker 1: absorbed from the is energy absorbed from the power to
Speaker 1: which the body is is exposed. It's best the best
Speaker 1: measure of ARF exposure, but it's difficult to measure. SAR
Speaker 1: varies with the frequency, power density, average amount of exposure,
Speaker 1: and duty of cycle of transmission. SAR depends on frequency
Speaker 1: and size of the body or body part affected. Highest
Speaker 1: where the body or body parts are naturally resonant. Safe
Speaker 1: levels of STAR based on are based on demonstrated hazards
Speaker 1: have been established by the FCC in the form of
Speaker 1: maximum permissible exposure limits or the MPE levels. Maximum permissible
Speaker 1: exposure MP limits vary with frequency because the body responds
Speaker 1: differently to energy at different frequencies. The controlled and uncontrolled
Speaker 1: limits refer to the environment in which people are exposed
Speaker 1: to the r F energy be taken into account the
Speaker 1: variation of the body sensitivities to r F energy at
Speaker 1: different frequencies. So you can see here that based on
Speaker 1: the frequency, the power density levels in a controlled and
Speaker 1: uncontrolled environment UH at different frequencies. So in this particular case,
Speaker 1: the this is where the body is more most sensitive
Speaker 1: to RF radiation mm HM. The limits of occupational controlled
Speaker 1: exposure UH. These are the you've got frequency range, the
Speaker 1: power density UH controlled environment in the in the uncontrolled
Speaker 1: environment ranges, controlled exposures limits supplies to control. The controlled
Speaker 1: exposure limits apply to individuals trained in r F exposures,
Speaker 1: such as the licensed amateurs. Uncontrolled environment is is those
Speaker 1: who is the general publics and their levels are just
Speaker 1: a different level, are just a different are are just
Speaker 1: a little higher. UH. The uncontrolled exposure limits apply to
Speaker 1: individuals not trained in r F exposure, so the general
Speaker 1: public UH. And you'll notice here. So so these are
Speaker 1: the frequency ranges and their exposure levels and the average
Speaker 1: time you you're required as an UH, you're required to
Speaker 1: do a UH UH an exposure analysis for your station.
Speaker 1: There's an r F calculator at the A at the
Speaker 1: a dobr L that allows you to put in some
Speaker 1: of these things here, such as such as UH transmitting frequency,
Speaker 1: antenna gain, and it will calculate the safe distance based
Speaker 1: on the exposure levels that you need to maintain. Okay,
Speaker 1: the things that control the duty, the things that are
Speaker 1: The things that control duty cycle UH and the uncontrolled
Speaker 1: environment are exposure RF energy, which is average over fixed
Speaker 1: time intervals. Time averaging evaluates a total RF exposure over
Speaker 1: a fixed time in two types of averaging periods are
Speaker 1: controlled and uncontrolled. The controlled is where you're aware of
Speaker 1: your exposure and are expected to take reasonable steps to
Speaker 1: minimize in controlled environment examples transmitting the controlled environment examples
Speaker 1: transmitting facilities near antennas. Uncontrolled environments are like general public
Speaker 1: asset our general public access. People in an uncontrolled environment
Speaker 1: are not aware of their exposure but are much likely
Speaker 1: to receive continuous exposure. Sure duty cycle is a ratio
Speaker 1: of the time the transmitter is on to the total
Speaker 1: time during the exposure. Maximum is one hundred percent, same
Speaker 1: as duty factor, but duty factor is expressed as a fraction.
Speaker 1: A lower transmission duty cycle permits greater short term exposure
Speaker 1: levels for a given average exposure. The less time the
Speaker 1: transmitter is on, the lower the average exposure, permitting greater
Speaker 1: short term exposure levels for a given average exposure. Along
Speaker 1: with operational duty cycle, the different modes themselves have different
Speaker 1: emission duty cycles. Operating duty factors of modes commonly used
Speaker 1: by amateurs. For most amateurs, operating listening and transmitting time
Speaker 1: are about the same, So duty cycle is rare really
Speaker 1: higher than fifty percent. Right. Calculating the average duty cycle
Speaker 1: power a station is using single side band without speech processing,
Speaker 1: transmitting listening for equal amounts of time and with transmitted
Speaker 1: power one hundred and fifty watch calculating the average outfoot power.
Speaker 1: Average duties power cycle is equal to the transmitted power
Speaker 1: times the emission duty cycle times of operating duty cycle.
Speaker 1: So if you've got a transmitting power of one hundred
Speaker 1: and fifty wats and uh, and you've got a duty
Speaker 1: cycle for about twenty percent processing operating fifty percent of
Speaker 1: the time, then your average duty cycle power to be
Speaker 1: one hundred and fifty wats times twenty times fifty percent
Speaker 1: about fifteen watts. Let's see's back up at a section
Speaker 1: again here. Yeah, guys are talking. I know you guys
Speaker 1: are talking, but it's kind of affected me a little bit. No, no, no,
Speaker 1: it's okay. I just want to just redo a section
Speaker 1: talking about we're going to go back to uh figure
Speaker 1: I mean, I mean you guys. Uh. Let's go back
Speaker 1: starting with RF exposure section nine point two slide thirty two. Okay, okay,
Speaker 1: so I'm going to start here and you got I know,
Speaker 1: you got to talk, but if it's sort of contract
Speaker 1: me a little bit. And I was okay, yeah, yeah,
Speaker 1: I just figured let me go back and do that
Speaker 1: section again. Okay, is this the last section? Yeah, this
Speaker 1: is the last thing. We're thirty two sixty four at
Speaker 1: thirty two slides left and we're done. Ok But I
Speaker 1: was more reading. I was getting a little it didn't
Speaker 1: sound too good what I was doing. So yeah, well
Speaker 1: that's up. Let me look at this see if you
Speaker 1: got enough, if you got enough time, find you got
Speaker 1: thirty six minutes levels. Okay, I think I can do that. Yeah,
Speaker 1: so you all be on the same file. Yeah, okay,
Speaker 1: so we're going to start RF exposure again. Okay, okay,
Speaker 1: so you can find this chart and sorry about that.
Speaker 1: I just want to make sure I just sounded pretty good. Okay,
Speaker 1: we're going to talk about our exposure. This has to
Speaker 1: do at at high power levels. For some frequencies, the
Speaker 1: amount of energy that the body absorbs can be a problem. Uh,
Speaker 1: there's a maximum permissible exposure called MPE, and that's the
Speaker 1: maximum intensity of r IF radiation to which a human
Speaker 1: being can be exposed. Factors to consider when calculating your
Speaker 1: MPE are transmit power level or density, the frequency, the
Speaker 1: average exposure time, and the duty cycle of the transmission,
Speaker 1: which is power density and frequency are the primary ones here.
Speaker 1: Stations with a time average transmission of more than one
Speaker 1: milliwat are subject to the FCC's r IF exposure rules.
Speaker 1: If your station exceeded the exemption criteria, you will need
Speaker 1: to evaluate it according to the FCC, and it has
Speaker 1: an OEt bullet in sixty five. The ABRIL has a
Speaker 1: online calculator where you can go calculate what the RF
Speaker 1: exposure is or how what's the minimum distance someone needs
Speaker 1: to be from your transmitting and transmitting antennum. And we're
Speaker 1: going to talk about there's two environments. We'll talk about
Speaker 1: power density first. U power density is heating from exposure
Speaker 1: to RF signals is caused by the body tissues absorbing
Speaker 1: r F energy. It's measured in wats per milliwats per
Speaker 1: centimeter square. R F field strengths can also be measured
Speaker 1: in volt super meter or amps per meter, but milli
Speaker 1: wats per meter centimeter squared is the most useful for
Speaker 1: amateur requirements. The power density is highest near your transmitting
Speaker 1: antennas and the directions of which the antennants have the
Speaker 1: most gained. Decreasing the transmitting power that the transmitter power
Speaker 1: and increasing the distance from the antenna will lower the
Speaker 1: power density, and vice and vice versa. The absorption in limits,
Speaker 1: there's a unit called SAR, which is a specific absorption rate.
Speaker 1: Is the rate at which energy is absorbed from the
Speaker 1: power from from power to which the body is exposed.
Speaker 1: It's it's the best to measure you are if exposure,
Speaker 1: but it's sometimes it's best to measure, but sometimes it's
Speaker 1: difficult to go back to actually do it. And it
Speaker 1: varies from with frequency, power density, average amount of exposure,
Speaker 1: and duty cycle. All those are factors that come into
Speaker 1: the SAR. The SAR measurement and also depends on the
Speaker 1: frequency and size of the body and the body part affected.
Speaker 1: UH It's it's highest where the body and the body
Speaker 1: parts are naturally resonant. Safe levels of SAR are based
Speaker 1: on demonstrated hazards and have been established by the FCC
Speaker 1: in the form of maximum permissional exposure limits. So they've
Speaker 1: taken all this to effect and they've come up with
Speaker 1: the thing called the mp ees. M p E is
Speaker 1: the maximum PERMISSIONBLE exposure. And these limits vary with frequency
Speaker 1: and UH. And they've they've come out and characterized the
Speaker 1: the the MPE based on frequency and power densities. And
Speaker 1: this chart here shows that. And there's two levels. There's
Speaker 1: a controlled environment in an uncontrolled environment. The controlled environment
Speaker 1: is where UH. The controlled environment is is is where
Speaker 1: the people are are aware of the are aware of
Speaker 1: r F and UH usually controlled by m can be
Speaker 1: controlled by UH access. Let's see, I'm gonna do this
Speaker 1: chart again. Okay, we're doing yeah, you and milling them
Speaker 1: with respact to get up, doctor. That's okay, okay. Maximum
Speaker 1: permissible exposure or MP limits vary with frequency because the
Speaker 1: body responds differently to energy at different at different frequencies.
Speaker 1: The controlled and uncontrolled limits refer to the environment in
Speaker 1: which people are exposed to the r IF energy. These
Speaker 1: take into account the variations in the body's sensitivity to
Speaker 1: r F energy at different frequencies. The limits for occupation
Speaker 1: and controlled exposure are shown here. The controlled exposure limits
Speaker 1: apply to individuals trained in RF exposure, such as licensed amateurs.
Speaker 1: Uncontrolled exposure limits applied to individuals not trained in RF exposure,
Speaker 1: so usually that's the general public. Okay. Exposure of r
Speaker 1: F energy is averaged over fixed time intervals. Time averaging
Speaker 1: evaluates that the total r F exposure over a fixed
Speaker 1: time energy two types of averaging periods. There's the controlled
Speaker 1: and the uncontrolled. And the controlled averaging you're aware of
Speaker 1: your exposure and are expected to take reasonable steps to
Speaker 1: minimize Controlled environment examples include transmitting facilities near antennas. An
Speaker 1: uncontrolled environment would be like public access. People are in
Speaker 1: an uncontrolled environment are not aware of their exposure, but
Speaker 1: are much less likely to receive continuous exposure. Duty cycle
Speaker 1: is the ratio of the time the transmitter is on
Speaker 1: to the total time during exposure. Duty cycle is expressed
Speaker 1: in a fraction instead of twenty five percent, So a
Speaker 1: lower transmission duty cycle permits greater short term exposure levels
Speaker 1: for a given average exposure. Called operational duty cycle, the
Speaker 1: less time the transmitter is on, the lower the average exposure,
Speaker 1: permitting greater short term exposure levels for a given average exposure.
Speaker 1: So along with operational duty cycle, the different modes themselves
Speaker 1: have different emission duty cycles. Twenty to forty percent duty
Speaker 1: cycle if you're doing a single side van with AFSK
Speaker 1: or slow scan TV, that's one hundred percent single side
Speaker 1: excuse me, and voice amplitude like AM modulation is fifty
Speaker 1: percent twenty one hundred percent. AM modulation is twenty five
Speaker 1: percent duty cycle FM voice one hundred percent duty cycle
Speaker 1: digital FM one hundred percent. So that all the digital
Speaker 1: modes that we use that we talked about are one
Speaker 1: hundred percent duty cycle modes like j like JTA. When
Speaker 1: your transmitters on is we consider it's one hundred percent
Speaker 1: duty cycle. Okay. Calculating the average duty cycle a station.
Speaker 1: If a station is using single side van without speech processing,
Speaker 1: transmitting and listening for equal amounts of time, and when
Speaker 1: transmitting power of one hundred and fifty watts, how how
Speaker 1: would we calculate that average power output? So the average
Speaker 1: duty cycle power is the transmitted power times the emission
Speaker 1: duty cycle at times of operating duty cycle. So in
Speaker 1: this particular case, we've got one hundred and fifty watts,
Speaker 1: where we've got an emission duty cycle for single sideband
Speaker 1: about twenty percent, and are operating duty cycle is fifty percent,
Speaker 1: So our average duty cycle power I got one hundred
Speaker 1: and fifty watts, but on times twenty percent of my
Speaker 1: mission duty cycle times transmitting fifty percent of the time,
Speaker 1: I get fifteen watts if you want to. If you
Speaker 1: all fixed ameateur stations must evaluate their capability to cause
Speaker 1: RF exposure no matter whether they are using high or
Speaker 1: low power. Limits vary with frequency and PEP. You're required
Speaker 1: to perform the evaluation that your power exceeds the level
Speaker 1: shown for any band. The r IF exposure evaluation is
Speaker 1: limited by three different methods during r F field strength
Speaker 1: with calibrated meters UH using the computer or model calculating
Speaker 1: to calculate your exposure or the easiest way is to
Speaker 1: use the a double r l's online calculator for r
Speaker 1: F exposure. So what you need to do to use
Speaker 1: the exposure calculator is what's the power of your antenna
Speaker 1: including adjustments for feed for for a duty cycle and
Speaker 1: feed line loss. UH. You got to know your antenna gain,
Speaker 1: your high above ground, and you're operating frequency. And when
Speaker 1: you have those items, UH, you can go use the
Speaker 1: exposure calculator to figure out, UH what the exposure is
Speaker 1: around your antenna system. When when when you UH, what
Speaker 1: what I've done for my home is I've got I
Speaker 1: know what antennas I have, I know what operating modes
Speaker 1: I use, and I go run that calculation through that
Speaker 1: a double r L calculator. I print those out and
Speaker 1: I've got those at my station, so I know uh
Speaker 1: how far or how close uh people can can can
Speaker 1: be to my systems. And for my home use, I'm
Speaker 1: in pretty good shape. I've got an unfenced backyard. But
Speaker 1: at the my my worst case is like ten feet
Speaker 1: from the end from from the end from the antenna,
Speaker 1: and all my intentors are ten feet above the ground.
Speaker 1: So my my RF exposure analysis shows on them in
Speaker 1: pretty good shape. Whenever I go to a public service event,
Speaker 1: if we're out in the public like a field day,
Speaker 1: you should go to an exposure analysis of the antenna's
Speaker 1: that you're going to be used. And you should. And
Speaker 1: if you've gotten an area where the public can get
Speaker 1: close to antennas, then you're gonna have to use some
Speaker 1: barriers to market offer to keep people away. Okay, so
Speaker 1: here's some good practices for RF exposure. You know, locate
Speaker 1: and move antennas away from where people can be exposed
Speaker 1: to excessive r F fields. Locate the antenna's a away
Speaker 1: from property lines and place fencils around the base of
Speaker 1: the ground mounted antennas. Don't point gain antennas where people
Speaker 1: are likely to be. Use beam antennas to direct RF
Speaker 1: energy away from the people. When using stealth, addict or
Speaker 1: indoor antennas. Make sure your MP limits are not exceeded
Speaker 1: in your living quarters. VHF and UHF. Place mobile antennas
Speaker 1: on a roof or trunk of a car to maximize
Speaker 1: shielding of fasseters. Use dummy load or dummy antennas when
Speaker 1: testing a transmitter, and of course, reduce the power and
Speaker 1: duty cycle of your transmissions. Yeah, here's some questions. What's
Speaker 1: one of the ways that RF exposure can affect human
Speaker 1: body tissues? It can heat up the body tissue. That's
Speaker 1: what ARF exposure do is you can feel it as heat.
Speaker 1: You'll hear people talk about RF burns. Which of the
Speaker 1: following is used to determine ARF exposure from a transmitting signal,
Speaker 1: power density, duty cycle? All of these are correct. All
Speaker 1: those affect how much your R exposure. How can you
Speaker 1: determine that your station complies with FCC RF exposure regulations?
Speaker 1: You can calculate it using the FCC OEt bulletin Computer
Speaker 1: modeling using fill screen. All those are are ways in
Speaker 1: which you can measure your compliance with RF exposure. What
Speaker 1: does time averaging mean when evaluating RF radiation exposure? See
Speaker 1: average amount of time powers applied by the transmitter average time.
Speaker 1: It's a total time. It's a total RF exposure over
Speaker 1: a certain period. It would be d What must you
Speaker 1: do if an evaluation of your station shows that the
Speaker 1: artific energy radiated by your station exceeds permissible limits for
Speaker 1: possible human absorption, take action to prevent exposure to the fields?
Speaker 1: Filing it impact FCC Secure written permissions. It would be
Speaker 1: a take action to prevent human exposure in the excessive
Speaker 1: r F fields. What must you do if your station
Speaker 1: fails to meet the FCC RF exposure exemption criteria? All right,
Speaker 1: so what must you do if your station fails to
Speaker 1: meet the FCC RF exposure criteria? So what you want
Speaker 1: to do is a perform an RF exposure evaluation according
Speaker 1: to those bulletins. Okay, what is the effect of modulation
Speaker 1: duty cycle on RF exposure? The higher the duty cycle
Speaker 1: creates let's see, ye, the higher the duty cycle from
Speaker 1: its greater power levels to be transmitted. That makes sense.
Speaker 1: The more your transmitters on, the higher the RF exposure
Speaker 1: will be. Which of the following steps must an amateur
Speaker 1: operator take to ensure compliance with FCC regulations. Let's see
Speaker 1: POST a copy performer. Yeah, it's going to be C performer.
Speaker 1: Routine art exposure valuation to prevent access to any identified
Speaker 1: high exposure areas. Okay? And what type of instrument can
Speaker 1: be used to actually measure r F field strength? Let's
Speaker 1: see BB a calibrated field strength leader with a calibrated antenna.
Speaker 1: What should be done if evaluation shows that a neighbor
Speaker 1: might experience more than the allowable RF limit exposure from
Speaker 1: the main lobe of a directional antenna? You can change
Speaker 1: the antenna height game use an antenna with the higher
Speaker 1: front the bank. Take precaution to ensure b C. Take
Speaker 1: precautions ensure that your antenna cannot be pomed in the
Speaker 1: direction when they are present. Okay, what precaution should you
Speaker 1: take if you install an outdoor transmitting antenna b C.
Speaker 1: Make sure the MPE limits are not exceeded in occupied areas. Okay.
Speaker 1: What stations are subject to FCC rules on RF exposure?
Speaker 1: That would be d all stations with the time average
Speaker 1: transmission of more than one mili a lot. Okay, talk
Speaker 1: a little bit about it. Outdoor safety installing antennas, make
Speaker 1: sure you place all antennas and feed lines well clear
Speaker 1: of power lines. No part of an antenna system should
Speaker 1: be closer than ten feet from power lines. When working
Speaker 1: on roofs, trees, or towers, climbers, helpers should wear appropriate
Speaker 1: protective gear at all times. Run through a safety check
Speaker 1: list every time, turn off and unplugged all AC equipment,
Speaker 1: locking circuits out and tagging them if possible. Transmitters should
Speaker 1: be off and it's connected from feed lines to avoid
Speaker 1: shock or excessive arf exposure. Belts and harnesses must be written,
Speaker 1: must be within their service life and attically rated for
Speaker 1: the weight. Of course, check check the weather report, and
Speaker 1: of course take your time. Here's some practice questions. Which
Speaker 1: of these choices should be observed when climbing a tower
Speaker 1: using a safety harness. Confirm that the harness is ready
Speaker 1: for the weight of the climber and that is within
Speaker 1: its allowable service life. Be done Before climbing a tower
Speaker 1: that supports electrically powered devices, You should be make sure
Speaker 1: all circuits that supply powers to the tower are locked
Speaker 1: and tagged out. Are locked out and tagged