locked Re: FST4 modes with TS-890S - slow RF envelope rise problem #txaudio


Hi all,

Rik, thanks for sharing your driver circuit. I can't really say I understand it yet, but I will save it for reference.

Peter, I would be interested to see your first circuit and also the one you are now working on.

My FET driver has an enable pin. It will not provide gate drive to the FETs until that pin is pulled low. I have just been leaving it hard wired low, as that works for all modes except FST4(W). I also 'works' for these modes but I have alarming waveform glitches, especially at the start and end of transmissions. I was thinking about sampling the RF drive, rectifying it, and feeding a comparator with reference level set to pull the driver enable pin low when the input waveform has reached sufficient amplitude to be 'safe'. This may not be the best approach but for now it is what I know how to do.

Let's hope it's not too late for the developers to consider a change to the software, as that would be the best solution.

Paul N1BUG

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