Speaker 1: Section thirty two of the Science History of the Universe,
Speaker 1: Volume three. This is a LibriVox recording. All LibriVox recordings
Speaker 1: are in the public domain. For more information or to volunteer,
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Speaker 1: Science History of the Universe, Volume three, edited by Francis
Speaker 1: Rolt Wheeler. Electricity, Chapter eleven, Part two. It was at
Speaker 1: once first seen by many experimenters, among them Sir Oliver Lodge,
Speaker 1: that with the old forms of apparatus there would be
Speaker 1: interference between wireless stations, as the receivers would respond to
Speaker 1: all wavelengths. To understand how it is possible to make
Speaker 1: as sending or a receiving circuit which will send out
Speaker 1: or respond to only one kind of electric wave, let
Speaker 1: the pendulum analogy again be used. In order to set
Speaker 1: a pendulum in motion, it is necessary that the impulsive
Speaker 1: force should be imparted to it the same number of
Speaker 1: times per second in which the pendulum naturally oscillates. Even
Speaker 1: if stray forces are applied but are not properly timed,
Speaker 1: the effect on the pendulum will be small, whereas a
Speaker 1: very minute but properly timed force acting for some time
Speaker 1: will produce considerable motion in a large pendulum. All these
Speaker 1: characteristics of the pendulum may be applied to the electric circuit,
Speaker 1: the natural period of vibration, the small effect of a
Speaker 1: lot of waves differing in length, and the large effect
Speaker 1: of a succession of feeble but similar waves. Sir Oliver
Speaker 1: Lodge in eighteen ninety seven took out a patent for
Speaker 1: a syntonic system of wireless telegraphy based directly on his
Speaker 1: own work on the discharge of latent jars and on
Speaker 1: Hertz's experimental results. The transmitter consisted of two large cones
Speaker 1: of sheet metal, placed with their axis in a vertical
Speaker 1: line and having a spark gap between their apecies. In
Speaker 1: another form of transmitter, a single stole metal sphere separated
Speaker 1: by small spark gaps from the terminals of an induction
Speaker 1: coil was used as a radiator. Both types produced direct
Speaker 1: Hertzian radiation, the latter giving waves of very high frequency.
Speaker 1: The spherical oscillator was partially enclosed by a copper cylinder
Speaker 1: open at one end in order that the rays might
Speaker 1: be condensed in one direction. The receiver for use in
Speaker 1: connection with the large cones consisted of two smaller cones
Speaker 1: connected through the primary of a small transformer, the secondary
Speaker 1: of which was connected to the coherer circuit. The dimensions
Speaker 1: of the transmitter and receiver were adjusted to give ecifrequent
Speaker 1: natural vibrations and therefore resonance. No earth connection was made,
Speaker 1: as it was desired that the transmission should be purely
Speaker 1: by means of free radiations. The early conical form of
Speaker 1: radiator has now given place to the horizontal conductors. Stations
Speaker 1: in which this latter arrangement has been adopted are now
Speaker 1: working in various parts of the world. As soon as
Speaker 1: Marconi had modified his system of telegraphy, he applied it
Speaker 1: immediately to the conquest of record distances in radio telegraphic transmission.
Speaker 1: To this end, he set up a station at the
Speaker 1: Lizard Cornwall, which was immediately put into communication with Marconi's
Speaker 1: experimental station at Saint Catharine's Isle of Wight, at a
Speaker 1: distance of three hundred kilometers about two hundred miles, in
Speaker 1: which he used an aerial conductor consisting of four vertical
Speaker 1: wires standing about five feet from one another about one
Speaker 1: hundred and forty four feet in height, along with a
Speaker 1: strip of wire netting of the same length under the
Speaker 1: new system, the energy required to telegraph to a given
Speaker 1: distance was very much diminished, so that one hundred and
Speaker 1: fifty watts sufficed to communicate to the three hundred kilometer distance.
Speaker 1: Encouraged by the results of the experiments in communication between
Speaker 1: Saint Catharines and the Lizard, Marconi put his whole heart
Speaker 1: into the attempt to resolve the artous problem of establishing
Speaker 1: transatlantic radio telegraphic communication. Repeated experiments had shown that long waves,
Speaker 1: either by successive reflection or diffraction, could turn round the
Speaker 1: surface of the Earth, so that their transmission to very
Speaker 1: great distances resolved itself only into a question of sufficient
Speaker 1: power in the transmitting apparatus and sufficient sensibility in the
Speaker 1: receiving But these necessitated large financial means, which would, however,
Speaker 1: not be wanting in a man whose business acumen was
Speaker 1: not less surprising than his experimental ability. Being largely subsidized
Speaker 1: by the Marconi Wireless Telegraph Company, Marconi began early in
Speaker 1: nineteen oh one, unknown to everyone, his trials, by establishing
Speaker 1: two specially powerful stations, at Poldew near Cape Blizzard and
Speaker 1: Cornwall on one side of the ocean, and at Cape
Speaker 1: cod in Massachusetts on the other side. The results of
Speaker 1: these first trials are not known, and, judging by the
Speaker 1: sou islands maintained in this regard, they were probably negative.
Speaker 1: The two stations, that had cost the sum of more
Speaker 1: than fifteen thousand pounds were destroyed by storms. In September
Speaker 1: of the same year. Marconi caused the station at Pouldu
Speaker 1: to be rebuilt, furnishing it with powerful machines and radiators,
Speaker 1: and decided to attempt communication with Saint John's Newfoundland, that
Speaker 1: is to say, to a lesser distance than that previously
Speaker 1: chosen of about fifteen hundred miles at Saint John's Newfoundland,
Speaker 1: where Marconi had obtained from the government every facility for
Speaker 1: making the trials. The installation was of the simplest character,
Speaker 1: consisting of a receiving station only. The area line was
Speaker 1: maintained at a height of about four hundred feet by
Speaker 1: means of a kite. Marconi had already agreed with the
Speaker 1: station at Pauldo that every day, at six o'clock in
Speaker 1: the evening, a long series of letter s should be sent.
Speaker 1: This letter, in the Morse alphabet, consists of three dots.
Speaker 1: The message was received telephonically on the twelfth of December
Speaker 1: nineteen oh one, Marconi announced that he had received the
Speaker 1: different ESS's at equal and determinate intervals, and he proclaimed
Speaker 1: that it was practically, physically and mathematically impossible that the
Speaker 1: signals could have come from any other place but Cape Lizard.
Speaker 1: In the summer of nineteen oh two, mister Marconi made
Speaker 1: an interesting comparative test of his first coherer system and
Speaker 1: his second magnetic detector system. The ship Carlo Alberta was
Speaker 1: fitted out with both sets of receiving apparatus. By previous arrangement,
Speaker 1: a set of signals from the Poldu station was to
Speaker 1: be sent out at certain hours of the day. As
Speaker 1: the voyage towards Kronstadt proceeded, the signals diminished in strength,
Speaker 1: and at a distance of nine hundred kilometers, were not
Speaker 1: perceptible during the day. At night, however, they continued to
Speaker 1: be received by both systems until the port of Karnstadt
Speaker 1: was reached, when only the magnetic detector responded, and that
Speaker 1: only feebly. The disturbing action of daylight was very marked
Speaker 1: in these tests. Having received an invitation from the Canadian
Speaker 1: government to continue his experiments in Canada, Marconi erected a
Speaker 1: large station at Tablehead on the island of Cape Breton,
Speaker 1: at the mouth of Glace Bay, and thirty eight hundred
Speaker 1: kilometers from Poldew. On December twentieth, nineteen oh two, mister
Speaker 1: Marconi sent the first radiograms across the Atlantic to the
Speaker 1: Kings of England and Italy. Shortly afterward, another station was
Speaker 1: erected at Cape cod in Massachusetts, the distance to the
Speaker 1: Poldu station being thirty two hundred miles or six hundred
Speaker 1: and sixty miles further than the Glace Bay station. On
Speaker 1: January sixteenth, nineteen oh three, a complete radiogram was sent
Speaker 1: by President Roosevelt to the King of England. Professor Fessenden
Speaker 1: commenced in eighteen ninety seven the development of the system,
Speaker 1: which is now the property of the National Electric Signaling Company.
Speaker 1: For two years he was engaged by the United States
Speaker 1: Government for special research in the subject, and had the
Speaker 1: advantages of all the resources of a government department at
Speaker 1: his command. His inventions are very numerous and in many
Speaker 1: respects original, and his results show a precision and a
Speaker 1: practicality not attained by many other experimenters in the same field. Magnetic,
Speaker 1: thermal and electrolytic detectors, methods of exact tuning, and even
Speaker 1: wireless telephony are covered by Fessenden's patents. Among these, perhaps
Speaker 1: that which has contributed most to the success of the
Speaker 1: system is the burrider. In its original form, this was
Speaker 1: a thermal receiver depending for its action on the change
Speaker 1: of resistance in a very fine platinum wire when carrying
Speaker 1: the jig current. Latterly, the continuous wire has been discarded
Speaker 1: in favor of an electrolytic coil, one electrode of which
Speaker 1: is an extremely fine point. The apparatus has been described
Speaker 1: more fully under wave detectors. An important feature of this system,
Speaker 1: which greatly aids secrecy of transmission, is the arrangement of
Speaker 1: the sending key, which does not break the circuit, but
Speaker 1: merely alters the wavelength of the waves given out by
Speaker 1: cutting out some inductance. Thus, unless a receiving station is
Speaker 1: tuned with extreme accuracy to the transmitter, it will receive
Speaker 1: instead of signals, only a long continuous dash. Hence, only
Speaker 1: a very sharply tuned receiver will receive a message at all.
Speaker 1: In the latest forms of apparatus, the difference in frequency
Speaker 1: between the waves sent out during spaces and those sent
Speaker 1: as signals is only one quarter percent. Interception by rivals
Speaker 1: is therefore almost impossible. Festenden is apparently the first to
Speaker 1: use an aerial consisting of a steel tube standing on
Speaker 1: an insulating foundation and held in position in insulated stays.
Speaker 1: The following guarantees are made for the festened In system
Speaker 1: by the holding company. Guarantee for a distance one kilowat
Speaker 1: set two hundred fifty miles, five kilowat sets four hundred miles,
Speaker 1: twenty kilood sets seven hundred to seven hundred and fifty miles.
Speaker 1: Guarantee for the prevent used to prevent other sending stations
Speaker 1: from interfering with the receipt of messages. Where the distance
Speaker 1: of the interfering station from the receiving station is more
Speaker 1: than one percent of the distance between the sending and
Speaker 1: receiving stations, a difference in wavelength of three percent is
Speaker 1: sufficient to cut out the interference without the signals being
Speaker 1: appreciably weakened, interfering and sending stations being of equal power.
Speaker 1: Guarantee for the secrecy center. With our latest form of
Speaker 1: secrecy center, the variation in wavelength is guaranteed to be
Speaker 1: only one quarter percent between space and dots. We guarantee
Speaker 1: that no other system can read the messages. Guarantee for
Speaker 1: wave measurer. We guarantee this device to be capable of
Speaker 1: detecting difference of wavelength of one quarter percent, and to
Speaker 1: be capable of measuring wavelengths at a distance from the
Speaker 1: sending station. There are also devices whereby atmospheric discharges will
Speaker 1: not interfere with reception, and a device for modifying the
Speaker 1: intensity of emitted waves without altering their length communicate with
Speaker 1: nearby stations. A report giving a description of the fasten
Speaker 1: In system as applied to transatlantic signaling between Massachusetts and
Speaker 1: Scotland may be of interest here. The power is developed
Speaker 1: by a boiler engine alternator equipment having a maximum capacity
Speaker 1: of twenty five kilowatts sixty cycles current. A transformer steps
Speaker 1: up to the voltage to about twenty five thousand, thus
Speaker 1: charging the condensers, which are discharged by a means of
Speaker 1: a gap adjustable so as to effect the discharge at
Speaker 1: any desired point of the cycle. The receiver used is
Speaker 1: the liquid bretder in its latest form. The aerial is
Speaker 1: formed by a tower extending to a height of four
Speaker 1: hundred and fifteen feet above the ground level and supporting
Speaker 1: a sort of umbrella formed of wires at its top.
Speaker 1: The tower is essentially a steel tube three feet in diameter,
Speaker 1: supported every one hundred feet of its height by a
Speaker 1: set of four steel guys, there being thus sixteen guys
Speaker 1: in all. The tower is pivoted at its base on
Speaker 1: a ball and socket joint and is insulated from the
Speaker 1: ground for a voltage of one hundred and fifty thousand.
Speaker 1: The guys are insulated from the tower as well as
Speaker 1: from the ground. Besides, they are divided into fifty foot
Speaker 1: sections by means of strain insulators. One of the most
Speaker 1: serious problems to be solved was the construction of these
Speaker 1: strain insulators, which, while capable of safely transmitting the maximum
Speaker 1: stress of about twenty thousand pounds, also resist an electrical
Speaker 1: tension of fifteen thousand volts each. The maximum deflection of
Speaker 1: the top of the tower in a ninety mile hurricane
Speaker 1: is computed to be fifteen and a half inches. A
Speaker 1: wave chute, containing over one hundred miles of wire and
Speaker 1: extending over six acres is a very essential feature of
Speaker 1: the installation. On January third, nineteen o six, the first
Speaker 1: signals were received from the American Sex, and shortly afterward
Speaker 1: communication was established so that messages were freely exchanged at night.
Speaker 1: The intensity of the signals received by telephone was at
Speaker 1: times so great that the messages could easily be read
Speaker 1: with the diaphragm three inches from the ears of the operator.
Speaker 1: A station twenty miles distant from Brent Rock, using about
Speaker 1: thirty kilowatts and sending on a wavelength differing not much
Speaker 1: more than three percent from that of the Scottish station,
Speaker 1: was cut out while messages were received from Macrinhanish. A
Speaker 1: system differing in many respects from the other systems has
Speaker 1: been devised by Sir Oliver Lodge and doctor Meirhead. The
Speaker 1: rotating steel disc coherer described under wave detectors is used
Speaker 1: by them. Another feature is the use of two capacity
Speaker 1: areas at both sending and receiving stations, by the adjustment
Speaker 1: of which they may be brought into tune. This system
Speaker 1: has been installed in many places with great success, and
Speaker 1: although it has not yet operated over such distances as
Speaker 1: the US Marconi and Festendon systems, it compares favorably with
Speaker 1: them in syntonizing power and has the advantage of using
Speaker 1: the siphon recorder. The Telefunken system is based on the
Speaker 1: patents of Professor Slabby and Braun and of Count von Arco.
Speaker 1: It may be considered as striking a mean between the
Speaker 1: earlier systems of Marconi and lodgemere Head, though of course
Speaker 1: with many variations and elaborations. In detail, a system of
Speaker 1: wires similar to those used by Marconi forms the aerial
Speaker 1: and the earth connection is given by a large capacity
Speaker 1: as in the lodgemere heead apparatus, A coherer and receiving
Speaker 1: circuit in many respects similar to the Marconi arrangement is employed.
Speaker 1: The DeForest system has had quite an extended commercial application,
Speaker 1: especially in the United States. It has the advantage of
Speaker 1: very rapid signaling twenty five to thirty words per minute
Speaker 1: having been reached. Communication by this system has been established
Speaker 1: between Manhattan Beach, New York and Colon, Panama, a distance
Speaker 1: of two thousand in one hundred and seventy miles. The
Speaker 1: extension of wireless telegraphy and the study of the relations
Speaker 1: of electrical discharges in radioactive bodies bids fair to be
Speaker 1: the most fruitful of the fields of the immediate future.
Speaker 1: The age has been well called the Age of electricity,
Speaker 1: and much amazement, ever, is expressed that man should utilize
Speaker 1: so well a force concerning which he knows so little.
Speaker 1: The complete understanding of the phenomena of atomic force and
Speaker 1: of radioactivity may go far to unlock many of the
Speaker 1: closed doors of nature, and the electrical scientist of today
Speaker 1: is steadily approaching that understanding. End of section thirty two
Speaker 1: and end of the Science History of the Universe, Volume three,
Speaker 1: Physics and Electricity by Francis Rohl Wheeler