Image: English Channel microwave relay antennas 1931

Description: Parabolic antennas used in a 1931 experimental microwave relay link across the English Channel, one of the earliest experiments in microwave communication. The 10 foot (3 m) diameter dishes transmitted voice, telegraphy, and facsimile images over 1.7 GHz (18 cm wavelength) bidirectional microwave beams 40 miles between Dover, England and Calais, France. The microwaves were generated by a miniature Barkhausen-Kurz tube located at the focus of the transmitter dish behind the hemispherical shroud visible in the center; an identical tube at the receiver amplified the received signal. The radiated power was about one half watt. In this image the dish in the foreground is the transmitter, while the receiver dish in the background was located behind the transmitter to avoid interference. The demonstration was sponsored jointly by the International Telephone and Telegraph Company (ITT) and the Laboratoire du Materiel Telephonique of Paris, managed by G. H. Nash for the English and E. M. Deloraine for the French. Although this was planned as the prototype for a commercial microwave system, the sponsors found they could not compete with cheap underwater telephone cables. A commercial 300 MHz link was built in 1935, the first microwave relay system. Note man next to foreground antenna for scale. Caption: "Two similar parabolic mirrors serve as transmitter and receiver at each end of the cross-Channel link, the receiver placed back of the transmitter to avoid interference."
Title: English Channel microwave relay antennas 1931
Credit: Retrieved August 5, 2014 from E. E. Free, "Searchlight Radio With The New 7-inch Waves" in Radio News magazine, Radio Science Publications, Inc., New York, Vol. 13, No. 2, August 1931, p. 107 archived on American Radio History website
Author: E. E. Free
Permission: This 1931 issue of Radio News magazine would have the copyright renewed in 1958. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. [1] Search of the Renewals for Periodicals for 1957, 1958 and 1959 show no renewal entries for Radio News. Therefore the copyright was not renewed and it is in the public domain.
Usage Terms: Public domain
License: Public domain
Attribution Required?: No