Quoting Mal...
"This QRS business is severe on PA fets and some
psu's, especially the slower crawls. Anything beyond QRS 3 - 10 could be fatal
over long periods for most rigs. Any sudden antenna instability, windy
condx, showers then sunshine ie SWR variations are tricky at the vy slow speeds,
even the Decca Jeeps have been know to blow smoke in amateur
applications."
I don't buy that at all.
My station has run 24/7 for extended periods at max
power with a floppy vertical to deal with the 'Pacific breeze' and
rarely if ever have I lost a FET and never a power supply... All my FET failures
can be classed as operator error not environmental factors... My only FET death
this year was caused by arcing to my nearby 80m dipole. It arced for a
good 30minutes by the look of the grab I was sent and then one of the FETs in
the TX shorted...
The trick is ensuring good cooling and
sizing of the parts, particularly ferrites. If there is a danger to
the FETs its when you're doing that old switched carrier mode rather rapidly and
only if you haven't taken good care of the transients on the FET
drains ;-)
Sorry Mal but my observations during prolonged and
rapid weather changes don't indicate that amateur transmitters are so delicate
that they can't handle long QRSS dot modes... I've run my sinewave (QRSS
near-infinity) for weeks on end without trouble during all kinds of weather
events...
I have data if you want to see it...
Scott
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