I have been using a ricebox and a 3-500 one-holer at 150W carrier, and have been quite pleased with the results. Only needs about 6W carrier drive.
To get the fidelity of PWM, I have been wanting to build Class D PWM for some time. Joe, W6ISJ, gave me a brilliant suggestion: use a Class D stereo amplifier as the modulator and power supply for the RF deck! (DUH, palm slaps forehead, why didn't I think of that?!!)
I had been playing with the idea of making a 50W carrier Class D rig, to run either barefoot or for driving the one-holer. After Joe's suggestion, I have decided to move ahead with it. I ordered
https://www.parts-express.com/tpa3116d2-2x50w-class-d-stereo-amplifier-board-with-volume-control--320-699For ten bucks you get a complete PWM generator and modulator already built!! it uses a well documented TPA3116D2 IC. Has lots of built in fault protection and shutdown. Furthermore, it appears to be DC coupled throughout, with the attendant advantages.
Joe cautions run coax from the stereo amp to the RF deck, and filter the PWM products at the RF deck.
I will run the RF deck at 12.5 ohms and use a 30 v (Meanwell 28v switching power supply, cranked up a bit) to
run the rig. I may have to drop the RF deck impedance to 5.5 ohms (50/9) to get enough power out of
the stereo amp. Who knows at this point. I will keep you informed as things progress.
73, Rod