Ultra-high-frequency techniques applied to mobile and fixed communication services

The present paper outlines the communication techniques at present under development for ultra-high frequencies. The subjects discussed fall under the following headings:- (a) Valves. (b) Frequency control. (c) Modulation. (d) Power amplifiers and frequency multipliers. (e) Signal amplifiers. (f) Frequency changers. (g) Aerials. It is shown that from the great diversity of techniques available, a communication system can be designed to perform almost any desired function, so long as the distance from transmitter to receiver is less than the optical range. Examples of u.h.f. systems made and tested in Admiralty Signal Establishment are described. Particular attention is drawn to the fact that microwave sets can now be made with the same stability (measured in kc/s) as the average high-frequency set had before the war, and to the fact that microwave radio-telephone circuits can now be made with a signal/noise ratio of 80 db, the length of the circuit being the optical distance from transmitter to receiver.