With broadcasting in full swing, the biggest do-it-yourself boom of all time got under way; a high proportion of receivers were home-assembled. The typical valve set of the period had a regenerative detector with two transformer-coupled AF stages and sometimes a rather ineffective RF stage, stabilised by aerial loading or positive grid bias. Neutralizing of anode-grid capacitance was already known, but its use did not become widespread for several years. Cost of valve receivers was high, so many listeners used crystal sets with headphones.
The superheterodyne principle of reception was first described; this was one of the great basic inventions which got off to a slow start.
'Electromagnetic Screening', the subject of an article by R A (later Sir Robert) Watson Watt, seems a far cry from the author's future work in radar. More in character was his RSGB lecture 'Observations on Atmospherics' (using recording gear and direction-finding) reported later in the year. 'The greatest unsolved problem in radio-telegraphy is interference by X's'.