CV 1098 VT 98 MOV 'CHAIN HOME LOW' VALVE, 1936

Thoriated Filament version of the VT58 Pulsed Radar Triode of 1936.
The valves were used in the Chain Home Low transmitters during the beginning of WW2 of such importance in the Battle of Britain.
50 KWatts at 200Mhz using two valves in push pull, of pulsed power.
Developed from the ACT10, the air cooled version of the CAT15.
Re the VT98/98A
Both these valves were developed by GEC from the VT58 which had a pure tungsten filament.
The VT98 is shown as being equal to the CV1098 and the VT98A is equal to CV1580.
Both these valves had thoriated tungsten filaments resulting in much lower heater power and higher output power compared with the VT58. Comparing the two CV data sheets the only discernible difference is that the filament rating for the CV1098 is 8.25 Volts at 35 Amps and for the CV1580 it is 8.25 Volts at 37 Amps. It looks as though they beefed up the filament slightly in the VT98A possibly to increase reliability.

According to Brian Callick's book Metres to Microwaves. A pair of VT98 used as amplifiers could deliver 30KW peak in 3 microsecond pulses. The VT98 was also used as the output valve in CHL (Chain Home Low) radars where it could deliver 100KW peak.

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