Date of Design : 1928

Frequency range: 3000 - 25000  kc/s

Where fitted: Receiver Outfit QL - Note the top picture is the "B9 New" and the bottom " B9 Old".

Quote.....B9 is designed as the HF receiver in Sloops etc., normally employed on detached service.  It is no use for Fleet work owing to the fact that the amplifier is designed to oscillate and hence re-radiation takes place [see Admiralty Handbook of W/T {1931} paragraph 693[1].