This is a little piece of Radio Communication history in the form of a British ,Air Cooled, WW2 Admiralty Transmitting Triode Valve/Thermionic Tube CV1222/NT39/AT75. They were manufactured from the 1920s to the 1940s.
It has a large 4-pin bayonet base and external anode with integral finned radiator. The valve was suitable as an amplifier or oscillator down to 10 metres at full rating and down to 4 metres at reduced HT voltage. Marconi were thought to have used this type of valve in their transmitters.
A nice looking gadget for display in the vintage office, the filament is actually showing continuity; a sign that the valve is probably working!
Approximate Dimensions
Height: 21.5cm Diameter Base: 4.8cm
The triode is very faintly stencilled with:
ADMIRALTY
813
NT39
and the air ministry arrow
also: 5433C
Specification- see image
Filament: 10 V – 1.65 A Max. anode voltage: 1500 V Max. anode dissipation: 75 W Amplification factor: 22 Mutual conductance: 5.0 mA/V Anode impedance: 4200 ohms Max frequency for 75% anode rating: 37 MHz
