This is based on the VE4MA design. At 2.5kV anode voltage and with good air cooling, it puts out 250W easily with about 12.7dB of gain. It can be pushed up to 500W output, but thermal stability becomes a problem.

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The complete GI-7BT power amplifier. The air inlet is a 1" pipe filled with waveguide beyond cutoff material. Some of the air comes out of air out #1, and the remainder, aided by an exhaust fan, exits through air out #2 at the bottom of the cathode cavity. Note the feedthrough connections for filament voltage ("F" and "F + K").

The GI-7BT power amplifier showing the air inlet with waveguide beyond cutoff material and the anode water cooler.

The anode water cooler and plate blocking capacitor.