Vic,
I run a pair of grid-driven 813s, actually a number of pairs. See the
"single band kilowatt" in ARRL handbooks from the 60's, may also be there in
late `50s. Plus, the article's available to members on the web site.
I use option 3, and my "something else" was nothing for a long time. I do
keep an eye on the meters and can tell right away if I've forgotten to turn
my drive down. I suspect that if I put a brick on the key at 100 W,
something in my input network would fry long before the 813s -- they're hard
to kill. An excellent tube choice for the absent-minded.
Recently I added a 6 dB pad on the input, so it drives in class C with 40 or
50 W. This was to keep my exciter power away from the threshold where the
Elecraft K3 switches to its 100 W final amp, which made the power adjustment
too fiddly. You could do that to limit the input, but make it more like 8 or
9 dB. Drive will undoubtedly depend on the band so set it for the highest
drive you'll need and you'll never go dangerously far over. I used Caddock
MP9100 series resistors on a nice hunk of surplus heat sink.
Another option would be to arrange a fixed DC bias to go to the ALC on the
exciter when the amp is enabled.
73, Carl WS7L
> -----Original Message-----
> [mailto:amps-bounces@contesting.com] On Behalf Of Vic K2VCO
> Sent: Wednesday, April 21, 2010 8:39 AM
> To: Amps reflector
> Subject: [Amps] Thinking out loud
...
> 1) A grid trip circuit that will open the ptt line on
> excessive grid current,
> 2) A screen trip circuit, etc., or
> 3) Something else?
...
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