I have been working for some time to fathom the secrets of power amplifiers. I have been targeting 7MHz and an output of 5-10W. The output stage needs a load impedance according to this
This is the circuit I have come up with, sorry poor photo, click to enlarge,
5W 7MHz PA
Transistors 2N3904 - 2N5109 - IRF530
The gain is adjustable by the trimmer on the emitter of the first stage. With the supply at 13.8V an input of -2dBm gives a gain with outputs at each stage of +12dB, +20dB and +37dBm. The board copper is used as a heat sink and does not get excessively warm. An external 40m LPF is used, but could easily be included on the board - may need a little more space.
5W PA board,
the emitter resistor is made of 3 x 3R0s as I don't have any 2W 1R resistors.
Power output, via a 40m LPF, is an easy 5W @ 12V, with quite a bit more at 13.8V
Power output 50R
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