6BQ5/6HF5 MOPA

A 'deluxe' transmitter. A reflectometer is installed to control the Standing Wave Ratio when tuning the antenna.

This is a strange feature for a simple valve transmitter, because often the best matching can be simply achieved by use of a Neon lamp or a traditional lamp (respectively, for high impedance and low impedance antennas), looking for the maximum brightness. The only justification I was able to find for such a complication is that the 6HF5 is rated at greater power levels than the traditional 6146/807/6DQ6 PA tubes, and so ... the operator might want to be delicate during the tuning operations, so not to cook the expensive final amplifier active component.

Radioman, Sept. 2015