Sensibly equivalent¶ to:
The VR28 is the UK RAF pre-CV code for the commercial 220VSG. This exhibit does not look as if it is a Cossor valve and the RAF requirement would have been for multiple sources of supply..
The datasheet talks of manual control of the bias point. This was at a time before the widespread use of the superhet in UK domestic receivers and the TRF (Tuned Radio Frequency) or straight set was the norm.
The AM and crown. The UK Air Ministry logo.
The balloon envelope is 44 mm in diameter, and excluding the B4 base pins is 105 mm tall.
References: Datasheet & 1043. Type 220VSG was first introduced in 1931.
Absolute Maximum Operating Conditions¶
Updated August 24, 2015. shape:balloon construction:pinch type:tetrode age:1930.1940 base:b4 heater:2.0v pins:4 pin:1.g2 pin:2.g1 pin:3.f pin:4.f pin:tc.a