New Mosfet PA for remote operations
Last week on 50MHz I’ve lost the QSO with KH7Y due the low power when controlling my station from the workplace. I don’t want to leave the tube PA switched ON when not at home…
So I’ve built a compact solid state 6m amplifier using hardware found in the drawer
It doesn’t look good but works fine.
Mosfet are a couple of SD2933 mounted on a large heatsink, supply is 2x 50V 10A switching (about 30eu each on ebay) and an old laptop supply for biasing/services, output relay is a Magnecraft.
The design is a classic push-pull with input matching in a single step and output matching in 2 steps to keep “Q” at reasonable level.
I had to use a full 1/4 wavelenght balun as a phase splitter for a perfect balancement. I’ve tried also a lambda/16 balun with worst results.
Power output is somewhat greater than 500W with 11W input.
The output spectrum is good even without the use of a filter, thanks to the push-pull configuration that kills the 2nd (and the other even) harmonic.