Superheterodyne reception of micro-waves
14 October 1937
An account is given of the development and design of a superheterodyne receiver for wave-lengths of 17 cm., the receiver incorporating a stabilised intermediate frequency amplifier. The signal-noise ratios obtained were very variable on account of deep fading, but average figures for the superheterodyne receiver were of the order of 37 db, while the corresponding value for a super-reaction receiver was 18 db, showing an improvement of the same order as for the long and short-wave bands. The method of calibrating the receiver for use as a signal-strength measuring set is described. The results of such signal-strength measurements revealed the existence of an unexplained loss of the order of 30 db for 17-cm. transmission from Calais to Dover, the value obtained for the field-strength being approximately 4 muV/m., which is about 30 db less than that calculated on the basis of optical propagation.