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WHERE DID IT ALL START?
A CHRONOLOGICAL HISTORY OF THE DEVELOPMENT
OF RADIO
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Page 6
of 7 -
Alexanderson, RCA and Paul Godley |
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1914
- 1919
ALEXANDERSON’S Alternator –
World War 1. Ernst F. W. Alexanderson, Swedish-American, had helped
Fessenden build some of his earlier alternators. With this background,
Alexanderson was able to improve the alternator so that “smooth”
continuous waves of frequencies from 50,000 to 100,000 Cycles per second
(we know them as hertz today) could be generated.
These
inventions resulted in experiments in radiotelephony, for the purpose of
facilitating and improving long distance speech. The first test was made
by Bell telephone engineers in 1915. A low power transmitter was used on
wavelengths of 800 to 1800 metres. The results achieved were good enough
to warrant further tests with higher power. While
initial tests used tubes giving 15 watts power output, before the end of
1915 several hundred such tubes (sometimes as many as 500) were paralleled
to achieve high power. Larger transmitting tubes of the order of 100, 500
or 1000 watts were not developed until
All
of this was the forerunner to broadcasting, which commercially didn’t
make its appearance until 1920-21. The technical developments in speech
transmission without wires during this period were to point the way for
the broadcast industry that was to soon explode. Frank
Conrad, in 1919, a Pittsburgh amateur and Westinghouse engineer, began
broadcasting recorded music from his amateur telephony station located in
a garage at the rear of his house. His broadcasts were received with such
great enthusiasm by other amateurs in the vicinity, who invited their
friends and neighbors over to hear the “wireless music”, that much
newspaper publicity was given to his broadcasts. As a result, Westinghouse
officials, in 1920 decided to build a large station to conduct
broadcasting for the publicity and prestige it would bring to the company.
Station construction was rushed so that it was launched in time for the
Harding-Cox presidential election returns. This station later became the
very well known KDKA. Broadcasting in the U.S. went from one station in
1920 to 400 in 1922 and then to over 1400 stations in 1924. 1919
- 1921
Formation of the Radio
Corporation of America (RCA).
Until 1919 the British Marconi Company had dominated in all
By
the early 1920’s radio had well and truly arrived, with most of the
general public now fully It
had only taken 2500 years for radio to arrive. One can’t help but wonder
what the next 2500 years will do for the art of communication?
1915 Successful telephony experiments between America and Paris. The need was recognized for higher powered transmitting valves, with consequently higher vacuum. Forty to fifty watts was not a big enough valve anode rating to achieve long distance telegraphy at the low frequencies then in use. 1916 Ship radio installations were still using mostly used arc transmitters. New ships began to be fitted with valve transmitters and receivers. The production of "hard" (high vacuum) valves had commenced, and in June of that year, signals were successfully sent between Portsmouth (England) and Gibraltar. In that case the tungsten anodes of the valves were worked at 2000 volts, and a current of about 10 amps. was obtained in an aerial having a total resistance of 5 ohms. 1917 The English Marconi-Osram Co. commenced production of transmitting valves for the British Admiralty, and glass valves with anode dissipations of up to 150 watts were being made in this year. French authorities issued thousands of small valve transmitters and receivers for use in the First World War battlefields. 1919 The obsolescence of the spark transmitter definitely began. CW (Continuous Wave) transmission was in general use in big stations, usually produced by the Poulsen arc or HF Alternator. Silica enveloped valves were introduced, those with an anode dissipation of 1 kW being quite common. 1920 Thermionic valves were still somewhat limited in power capability and only used in small transmitters, since it was uneconomical to use a large number of small valves in parallel. 1922 Experimental valves rated at 100 kW had been produced, but 500 watt glass bulb transmitting valves were still the most common. Crystal control of frequency began to develop from this year. 1923 Demountable transmitting valves were produced, and two rated at 10 kW were installed at the Eiffel Tower. 1924 The beginning of the HF (High Frequency) era of commercial radio communication. Successful telephony between Poldhu (England) and Sydney (Australia). The invention of the copper-glass valve seal enabled a great increase to take place in the anode rating of valves; the anode became accessible and could be water jacketed in order to cool it. 1927 The British GPO (Post Office) opened a transatlantic telephone service using the "single side band" (SSB) system of transmission. The power of the transmitter was about 100 kW, and the final amplifier stage at first included thirty 10 kW water-cooled valves. 1931 A 500 kW demountable valve was installed experimentally in the GPO single side band transmitter.
BIBLIOGRAPHY |
So
great were the possibilities of these new alternators that Marconi himself
came to the G.E. laboratory to see a demonstration. As a result the
British Marconi Company began negotiating for the machine, but a stalemate
in negotiations was reached when the U.S. entered World War 1 and seized
or closed down all private wireless stations. Throughout the war wireless
was of substantial aid to both sides as a means of constant communication
and as an aid to espionage. In the United States the A.T.&T. Co. was
hard at work perfecting the vacuum tube, the rights to which it had
purchased from de Forest. The tube’s ability to function as an
“oscillator”, or generator of high frequencies, was established by
that time, by virtue of de Forest’s and Armstrong’s feedback circuits.
A means of modulating voice on the carrier wave that was produced, also by
vacuum tubes, was developed in 1914-15 in the G.E. Labs. by Alexanderson
and in the Western Electric Labs. by Colpitts. Hartley, working for
Western Electric, Co. in 1915 also developed the Hartley oscillator
circuit.
sometime
later. As a result of all of this research, in 1915 the first
trans-Atlantic (and, accidentally trans-Pacific to Honolulu)
radiotelephone conversations were successfully held between Arlington, Va.
and the Eiffel Tower in Paris. In these test the U.S. Navy, Western
Electric and A.T.&T. Co. all collaborated.
activities
of the American wireless field (in Australia it had been Telefunken and
Marconi who’s government forced marriage resulted in the formation of
AWA). Their early start and strong finances permitted them to buy up and
control all major patents and activities. After World War 1, the Marconi
Company resumed its negotiations for the Alexanderson alternator. The
United States government intervened. It was felt at the time, that the
sale of American patents might result in the domination of 
wireless
communication by foreign interests. After conferring with the navy, a
meeting was held at the General Electric office, where it was decided to
retain the alternator in the interests of the U.S. It was likely also, at
this meeting plans were formulated for the formation of a strictly
American-owned radio company. At any rate
conversant with its capabilities. The 1920’s brought many refinements in
valve circuit technique, for example Rinartz’s superior regenerative
receiver, Armstrong’s superegenerative and superhetrodyne receivers as
well as the neutrodyne receiver. By opening up low power trans-Atlantic
communication, the amateurs, through Paul Godley (using Armstrong’s
superhet receiver),
