Audion as an amplifier of radio signals, whether telegraphic or telephone, was far ahead of any other amplifier that has ever been developed. For several years, from 1907 to 1911, audion was used only as a sensitive detector for receiving radio signals. The general principles of his work were not understood. De Forest conducted some experimental work on the use of an audion amplifier as a telephone repeater, however, his early development was unsuccessful. This was due to the fact that he did not attach much importance to the amount of displacement on the grid of the audion. He tried to amplify a low-frequency signal (AF) with an offset value on a grid designed to amplify a high-frequency signal (RF). In 1912, the first sound amplifier was built by Fritz Lowenstein, a former employee of the Forest company.
audion, RF amplifier, John S. Stone, Otto von Bronk, Fritz Lowenstein, audio amplifier, Lee de Forest, cascade, cascade audio amplifiers
1. Bronk O. von. Patent für DRP271059 vom 3. September 1911 über eine “Empfangseinrichtung für drahtlose Telegraphie”.
2. Stone J. S. & Cabot S. Space Telegraphy. Patent US884110A. Application Field Jan. 4.1907. Patented Apr. 7, 1908.
3. Discussion of “A History of Some Foundations of Modern Radio-Electronic Technology” // Proceedings of the IRE. 1959. No. 7. P. 1254.
4. Lowenstein Fritz. Telephone relay. Patent US12478717A. Application Field Apr. 24, 1912. Renewed Apr. 26, 1917. Patented July 3, 1917.
5. History San Jose Research Library. History San Jose Online Catalog. URL: https://calisphere.org/item/d4cd7ae1bdfe0d0223fcf60bdce1c071/ (27.11.2020).
6. Discussion of “A History of Some Foundations of Modern Radio-Electronic Technology”// Proceedings of the IRE. 1959. No. 7. P. 1255.
7. De Forest’s diary, February 12, 1912; entry in his notebook, April 22, 1912, Papers of Lee de Forest, Library of Congress, Washington DC.
8. Mann F. J. Federal Telephone and Radio Corporation. A Historical Review: 1909-1946 // Sparks. 1974. Vol. 3. No. 11. P. 17.
9. Logwood C. V. High Speed Radio Telegraphy // The Electrical Experimenter. 1916. No. 6. P. 99-100.
10. Uglov A. E. Atlas chertezhey k kursu usilitel'nye lampy v telegrafii i telefonii bez provodov. Petrograd, 1917. 38 s.
11. Pestrikov Victor M. The invention of a tube audio amplifier // ITM Web of Conferences. Vol. 30. 16002 (2019). URL: https://www.itm-conferences.org/articles/itmconf/pdf/2019/07/ itmconf_crimico2019_16001.pdf (01.12.2020).
