Sensibly equivalent¶ to:
The PT15 HF RF amplifier is a modification of the M-OV civil Type PT5. The principal modifications included raising the voltage of the oxide-coated filament from 4 to 6, fitting a ceramic base cap and making the electrode assembly both lighter and more rugged, as befits airborne applications.
The whole point of the PT15 was simplicity and economy. Like the PT5, it was a true pentode whose suppressor grid was dimensioned to inject audio modulation at low power directly from a (transformer-coupled) carbon mike. This eliminated the need for a modulation amplifier: one less thing to go wrong! No wonder the famous T.1154 set of WWII was easy to make in vast numbers, light, easy to use and, above all, reliable! T.1154s, now 60 years old, are still sought after and used by radio amateurs.
The PT15 was used in WWII within transmitters fitted to bombers such as the Lancaster and Sunderland and many others. The master oscillator for the Marconi 1154/55 Bomber Set was an ML6. More details can be found in the Saga of the Marconi Osram Valve 1005.
So many of the PT15's were made that production numbers started to rival those of receiving valves. The CV1240 is a modified PT15.
The wide glass tube envelope is 48 mm in diameter, and excluding the B5 base pins, is 161 mm tall.
References: Private communication & .
Absolute Maximum Operating Conditions¶
Updated October 18, 2014.