We're thinking along the same lines. I tried a PWM modulator a few
months ago - it is shown in the latest LF experimenters book - but this
required an 8 bit digital input for the PWM. It could modulate rails up
to 50V at 10A but could be expanded. Tried the concept with a (badly
generated) PSK31 waveform on 1.8MHz with sucess, but the poor generation
due to the way I encoded the waveform using 6 bit amplitude sampled at
500Hz, generated unacceptable sideband levels at the 500Hz sampling
rate. Never carried on any further as this project was not a priority
then.
The only switching PAs I have at the moment are the experimental big
ones, so these look a contender for the next PWM supply controller.
There's a challenge, a 0-100% duty cycle 340V controller using PWM !
Andy G4JNT
If one is serious enough about civilized PSK sidebands to
consider linear
amplification-- which is no trivial matter at the "California
kilowatt" > Class C, D, and E amplifiers are not that hard to
modulate.
stages, apply PWM
methods to the power supply for the final!
> If the amplitude component and RF phase/frequency components
are reunited in
the final amplifier without excessive time difference, the >
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