I'm reading "the secret wireless war" and am surprised that the entire basis for transmitters throughout the British traffic network including spy radios and fixed stations transmission of decrypted ULTRA (Enigma) traffic to those with need-to-know was handled by a two tube 6V6 and 804 arrangement called the MKIII.

The secret service built them all themselves from the design in the ham radio handbook to avoid raising suspicions if they began buying the few commercial ham equipment.

That is the same arrangement as the first Novice transmitter I built back in 1963 in middle school just 18 years after the war. Amazing.

Bob, WB4APR.