With the increase in sensitivity of receivers and the growing electrification of the country, man-made interference had become a serious problem. Following suggestions made in Wireless World the IEE had set up a committee to consider the possibility of legislation and interference complaint questionnaire forms could be had from post offices. This service is still available to the public.
The 'small superheterodyne' was soon to become Britain's standard broadcast receiver: early versions had bandpass input, single-valve frequency-changer, one IF stage and a second detector feeding a pentode output valve. RF pentodes were by now widely used and the electron-coupled frequency-changer had appeared. Refinements like. Automatic gain control, noise-suppression switches and, occasionally, 'quiet' AGC, were coming in. For battery sets, economy circuits with push-pull output valves biased to cut-off were being used. Built-in car sets had arrived, so we described methods of suppressing ignition interference.
STC put up for the Air Ministry a decimetre-wave (17.5 cm) link working across the English Channel.