The CV1787 (commercially the FX2505) is a hydrogen thyratron designed for switching in-line modulator circuits of microwave radar with the 4C35 as the prototype. Other uses include induction heating and pulse modulation.
In essence this type of valve acts as a fast switch with low on resistance and momentarily connects a bank of charged capacitors across a magnetron and thus delivers a pulse of a high power for a few micro-seconds.
The KB/Q identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the Q identifies the maker as English Electric Valve Co., Chelmsford.
The anode lead is shielded within a glass tube and the anode clamps to this tube.
The glass foot. The earlier 4C35 was built on a pinch.
The anode is held at both the top and base. The base pins being sealed into the sintered foot but not taken to the external pins.
The wide glass tube envelope is 64 mm in diameter, and excluding the base pins is 157 mm tall.
