NOTE: I can no longer produce these amplifiers for sale due to the “15 dB rule” under Part-97 now that the Report and Order has been issued for 630-meters. Parts are available from Mouser and my notes are included below. If you are not a builder, don’t worry as someone will take advantage of the opportunity to design an amp that meets the 15 dB requirement in the very near future.
I have in the past assembled and tested “a few” amplifiers based on the GW3UEP design that include a few modifications to enhance efficiency, harmonic suppression as well as permit low level drive signals from exciters like the Elecraft K3S, Flex and Kenwood lines. See GW3UEP’s site for schematics and information on the basic, unmodified amplifier design. The basic non-linear amplifier schematic for use with constant amplitude and phase modes like WSQ2, Domino-EX, WSPR and JT9 can be found here. If you are a CW operator, look at this schematic as it includes a waveform shaping circuit that allows you to key the amplifier directly while driving with a VFO/DDS or other signal generator (use your receiver with a separate RX antenna for full break-in or build an RX/TX switch actuated by foot switch for manual control).
Construction notes and modifications to accompany these schematics can be viewed here.
Contact me if you have construction questions. I am happy to provide input.