I have investigated waveforms at every stage using all three
exciters here: exciter output, doubler output, IR2110 input, FET
gates, FET drains. I see no difference at any of these points
between exciters. However I cannot capture brief events that may
happen at the start or end of the RF envelope. I believe that is the
key.

I do find things don't look at good using the doubler was when I
made earlier tests using the HP 3325B without the doubler. I am
still rejecting the idea of running 2Fo drive from exciters as I do
not want to get locked into that requirement.

Undoubtedly I was trying to use the amp in ways Jay never intended
so I can't blame the design. Mine is now retired as I am unable to
get to the bottom of this issue with the limited test equipment at
my disposal.

73,
Paul



On 2/26/19 6:18 AM, Chris Wilson wrote:
> 
> 
> Hello N1BUG,
> 
> Just to add things were MUCH worst using a X2 multiplier circuit
> (Jay's). I now use an exciter frequency of X2 direct both from the
> U3S, and as of late X2 from the TS-590 into a simple squarer and use
> WSPR in the "Advanced" X2 mode to correct the WSPR tones. No issues at
> all with either. OPERA is a no no as of this time, it is a FET killer
> :)  Don't  know  why though. It would be great to get to the bottom of
> all this!
> 
> Tuesday, February 26, 2019, 11:05:15 AM, you wrote:
> 
>> Jay,
> 
>> I was using an HF transceiver in CW mode through a down converter.
> 
>> Other FETs were lost at end of envelope while running JT9 with the
>> transceiver in USB being fed audio from a sound card. The latest was
>> with audio from a different sound card into the new phasing exciter.
> 
>> I have never lost a FET while running with the U3S.
> 
>> 73,
>> Paul