> My main power supply is a 3670 0 3670 NATO transformer with inductive
> input filter.
Choke input filters generally have close to unity power factor, so
that make life with a variac somewhat better.
> My no load high voltage is variable 100 - 4850 volts.
Was is the NL/FL voltage regulation?
> The VARIAC after a Sundays use with above amps only gets hand warm.
Regulation is the issue, not temperature. With a choke supply you
have a much better power factor than with a capacitor supply.
> I used 100 watts (20 meter band) from my ICOM IC761 with the 4-1000A
> at 3500 volts and my YAESU wattmeter showed 2000 watts PEP.
Buy a new wattmeter, that reads correctly. Perhaps you have
accumulated errors, but you certainly do not have the gain at 3500
volts you think you have. I would say it is off by a factor of two or
more. I doubt you even have 1000 watts out with 100 watts of drive
with 3500 volts and a 4-1000A.
There isn't a cathode driven 4-1000A in the world at 3500 volts HT
that can have 13dB gain, unless it has a bad case of positive
regeneration. A 3CX1200 or 3-1000Z would barely, if at all, make
that gain.
73, Tom W8JI
W8JI@contesting.com
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