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Starting from LDMOS amplifier studies, I found that almost all class AB amps are identical designed these days. impedance down 4:1, symmetric LDMOS FET, 1:9 TLT to get back to 50ohms and a balun to arrive asymetric (coax) as an output.
Lucky me, I again found a great and maximally simple design very well made by the guys from eb104.ru. A nice head start, the unit comes assembled on a copper plate and works out of the box 500W - bang.
Some say it is not perfect above 20MHz. I probably will not ind that out as my World of frequencies is low. 1.5Mhz to 16MHz.
I did not see any more puristic schema yet, and I love the PCB layout. Super compact but easy to mod. add attenuators, switching, limit monitoring, and stuff now.
The major work is going now into safety cirquits. From my experiments I know how easy the mosfets catch fire. And fire is the only real danger I must avoid under all circumstances.
It is growing like a plant, and I am learning a lot. Now, having the working controller with nice measurements, I feel more confident. Patched together a two-tone oscillator for reproduceable amplitudes and a very basic VFO+Mixer since the SDR radio project is not even started.
ToDo1: design an LPF board with same dimensions as the controller board.
ToDo2: design smaller SMD input board with sequencer, ALC and smaller power switch with similar current/swr/voltage hardware cut-off cirquit. Do not trust the DSP for security.
ToDo3: Get a suitable heatsink for the full load test, make a 1kW dummy load.
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