Furthermore, if I make a small pick up coil (3 turns x 1 cm dia) and hang that off the probe, by holding near the respective inductors, I can see an intense and clean PWM waveform at the input to the filter and this dies away completely as I go down the filter chain. So, something looks as if it is working OK.
DMOD wrote:Furthermore, if I make a small pick up coil (3 turns x 1 cm dia) and hang that off the probe, by holding near the respective inductors, I can see an intense and clean PWM waveform at the input to the filter and this dies away completely as I go down the filter chain. So, something looks as if it is working OK.
It sounds like you are ok and I would put a dummy load on the RF out, modulate it, and look at the resulting waveform. The floating ground in the Modulator can cause some interesting probe waveforms if your scope isn't fully isolated.
I do know in my last conversation with Steve, he did change the gate resistors values in the PWM drive from 4.7 to 5.6 Ohms, IE, the R503 to R507 resistors that shunt the diodes.
Phil - AC0OB
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