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CV228 Heil tube, for use as an oscillator in the frequency range 4.4 to 4.85GHz. With a cathode current of 65mA, the minimum output at 4.65GHz is 450mW.

Heater voltage6.3V
Nominal heater current300mA
Grid voltage0 to -200V
Resonator voltage220V
Screen grid voltage0 to resonator voltage
Anode voltageResonator voltage + 10 to 20V
Min output power450mW
Max mean power input15W
Max peak current500mA
Tuning range6.2 to 6.8cm
Magnetic field1000 oersted

Base connections:

1 Grid
2 Cathode
3 Heater
4 Heater
5 Anode
6 Resonator
7 Screen grid

In operation the valve is held in a magnetic field, and the 'probe' above the disc would be inserted into a tuned cavity.

Also known as V246A/1K.

Two of these were used in the Wireless Set No. 10 Mk.II (CV79 and CV89 magnetrons were used in the Mk.I version)

CV228 side 1CV228 top closeupCV228 top view
CV228 in a boxCV228 box label
CV228 cardThe CV228 pictured came with a test certificate titled 'Broadcasting stations - transmitting tube record'. This shows the serial number of this valve to be LYQ5G and the first test date is 11/2/54, followed by 14/7/74. The tube is new and presumably never used other than being tested. Unfortunately because of this, the interesting area of the card ("Tube employed as") is blank!