Discussion of "A History of Some Foundations of Modern Radio-Electronics Technology" Page 1258

in relation to Hammond. In a letter of June 14, 1955, he replied: “Hammond’s works were entirely unknown in France in 1917.”

In the year 1920 the present writer, with the American Telephone and Telegraph Company, became aware that there was developing a considerable technique in the stepping of channels up and down in the frequency scale through modulation and demodulation in conjunction with amplification and frequency selection. He drafted two reports calling attention to the situation. They showed the existence of some fifteen patent applications internal to the Bell System, and some six inventions outside the Bell System, those of A. V. T. Day, Hammond, Meissner (the German), Lévy, Alexanderson, and Armstrong. Since the Bell System engineers were early in leading into this technique, a listing of their contributions will illustrate the evolution that occurred quite independently of Hammond:

1. Homodyne reception, i.e., zero-beat heterodyne, invented by B. W. Kendall in 1915, Patent No. 1,330,471 (1915–1920). Used in the transoceanic radio telephone tests of that year, including the present writer’s reception at Pearl Harbor, T. H.
2. Single-sideband transmission, wherein the carrier is resupplied at the receiving end by a zero-beat oscillator, invented by J. R. Carson in 1915, in conjunction with the same radio telephone development. Patent No. 1,449,382 (1915–1923).
3. A “static” neutralizing system receiving on two frequencies, beating one down, the other up, to a common frequency, for balancing. Espenschied Patent No. 1,309,400 (1916–1919).
4. Multiplex radio telephony wherein three intermediate carrier channels are modulated en-bloc upon a radio carrier, then demodulated, selected, and finally detected in individual channels. Installed on two U. S. battleships in 1916–1917, R. A. Heising Patent No. 1,633,100 (1916–1927). This same year B. W. Kendall pointed out that Heising’s multiplex system could operate with carrier suppressed, if resupplied at the receiving end by a zero-beat oscillator (recalled to the writer by Heising in 1957).
5. World War I intervened.
6. By the end of 1919, Carl R. Englund was using at Elberon, N. J., in the ship-to-shore radio telephone development, a three-channel superheterodyne receiver, according to the remembrance of Harald T. Friis and the writer.
7. Superheterodyne receivers were used on both the ship and shore ends of the development, 1919–1923. System described in paper by Nichols and Espenschied.³⁰
8. Double modulation and double detection were used in the radio telephone link established in 1920 between Catalina Island and the mainland, California. Carried a superimposed telegraph channel. (Proceedings of the IRE, December, 1921, and Bell Telephone Quarterly, October, 1923.)
9. About this same time, 1920, a superheterodyne receiver was employed to realize sharp selectivity and high gain, in a radio printing telegraph demonstration between New York, N. Y. and Cliffwood, N. J., for the delegates to a preliminary international conference on electric communications.³¹
10. 1922–1923, a superheterodyne field strength measuring set, made portable by means of loop and “peanut” tubes requiring modest battery, used in ship-to-shore development, later in broadcasting.³² Forerunner of the 4-A broadcasting receiving set referred to below.
11. 1922–1923, appearance of the first commercial superheterodyne developed for broadcast reception, the Western Electric 4-A. A copy of an engineering report on its development was given to Dr. Alfred N. Goldsmith of the Radio Corporation of America in October, 1922, and a model of the receiver itself was given to him a few months later for test purposes. This receiver was so superior to anything else available at the time that it “. . . literally gave Elmer E. Bucher and others responsible for RCA sales the jitters,” said Gleason L. Archer in his book, “Big Business and Radio” (1939, page 92).

Thus it is apparent that IF technology came into being and went into service quite independently of Hammond’s more secret efforts in the field.

FREQUENCY MODULATION AND RELATED SYSTEMS (SECTION V)

As the paper indicates, the idea of FM was of long standing, without meeting much success until practiced at the higher frequencies with a correspondingly wide frequency swing.

A Hammond patent is cited³³ which undertook to transmit radio telegraphy by the familiar frequency-shift keying of the Poulsen arc while simultaneously modulating both frequencies for telephony. But the arrangement was so crude as to be substantially inoperative: telephone reception would suffer key clicks; telegraph reception in the earphones would experience interference from the telephone channel. Such a “paper patent” can hardly be said to have “established that two independent communications could be sent on the same band . . .” (in fact de Forest had already done that). Certainly the disclosure of the patent was not what founded the modern practice of transmitting two chrominance signals in color television.

The presentation of the Chaffee transmitter of Fig. 16 as part of a “noise-reduction system” is misleading since the noise it undertook to reduce was that arising in the transmitter itself, not that of the transmitting medium.

It is appropriate for the authors to recall something of how wide-swing FM arose from the advance of radio to the higher frequencies, where the “natural atmospheric disturbances were of lessened importance.” As tube transmitters were pushed to these higher frequencies (of the order of 50 mc), the modulation of a radio telephone transmitter tended naturally to swing the frequency. Appearing initially as a fault, the making of a virtue of this effect was a natural second thought. Chaffee of the Bell Telephone Laboratories thus sought to utilize it and devised a receiver for an FM system. The printed announcement of a paper³⁴ he was to give was followed immediately by a press release by Prof. E. H. Armstrong of his own invention of FM, now so well-known. In the public demonstrations made by Armstrong he compared the high-frequency FM channel with an ordinary broadcast channel, giving the impression that all the noise improvement was due to his FM system, whereas perhaps half had been bestowed by Nature!

Altogether, the attainment of the higher frequencies by means of the vacuum tube was the primary force in bringing about modern FM, the inventors being those who were on the stage at the time seeking the new. No less is the honor owed to those who, through “inspiration and perspiration,” really gave it to the world.

LLOYD ESPENSCHIED
Retired Consultant
99 82nd Road
Kew Gardens 15, N. Y.

Rebuttal by John Hays Hammond, Jr. and E. S. Purington *

On February 3, 1958, we received the uncorrected nine-page galley sheets of a paper “Critique of the Hammond-Purington Paper Entitled ‘A History of Some Foundations of Modern Radio-Electronic Technology’,” by Lloyd Espenschied, a Fellow of the IRE. We appreciate the courtesy of the Editorial Board of the Proceedings in permitting us to publish this Rebuttal in the same issue in which the Critique also appears.

This Critique contains both material relating to and not relating to that con-

* Received by the IRE, March 31, 1958.
³⁰ H. W. Nichols and L. Espenschied, “Radio extension of the telephone system to ships at sea,” Proc. IRE, vol. 11, pp. 193–242; June, 1923.
³¹ R. A. Heising, J. Franklin Inst., vol. 193, pp. 97–101; January, 1922.
³² R. Brown, C. R. Englund, and H. T. Friis, “Radio transmission measurements,” Proc. IRE, vol. 11, pp. 115–152; April, 1923.
³³ Footnote 1, p. 1200, reference 43.
³⁴ J. G. Chaffee, “The detection of frequency modulated waves,” presented at Washington, D. C., April, 1935. Published in Proc. IRE, vol. 23, pp. 517–540; May, 1935.
—, “Application of negative feedback to frequency modulated systems,” Proc. IRE, vol. 27, pp. 317–331; May, 1939.