Series Cathode Modulator

a bit more critical than with the cathode modulation but. as can be seen from the photo, the pattern is about the same.

Using fi*cd bias in the neighborhood of 175 volts (this seems high but seemed to be the value for our particular 813 of unknown history) the amplifier works very well as a class B linear AM amplifier. Not having AM in the exciter pictured we used parts of an KCA demonstrator which had a single 6K6 plate and screen modulated- The plate voltage and current value of the 813 stage were about the same as with grid modulation. As can be seen from the patternf there is slightly more tendency toward flattening-

If the resting current were held to about 75 ma (to avoid too much voltage variation) the amplifier should work ok as a SSB linear. This was not tried.

All in all we got quite a bit in a very small box and it will serve very well for our portable needs which call for a little power.

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