ne1s wrote:
Geoff/W5OMR writes:
Does anyone have any 4-65's?
I think that'd be a neat little ~100w rig to build up.. a single 4-65
tetrode, modulated by a pair.
Sounds like a neat combination. You oughta be able to get about 150W
carrier out of one, run less conservatively (not that anyone will hear
the difference, of course).
Someday I am going to build a rig with a pair of 'em modulated by
811s, when I get a round tuit. Already have the HV PS/modulator deck
built, just have to do up the RF deck, which will also contain the VFO
(a T-195 PTO I've been saving for this project), and RF and AF driver
circuits. I hope to run the pair at 500W input (2500V @ 200 mA), or
close to it, depending on the plate efficiency I'm able to achieve.
Oh, now -there's- an idea... a pair of 811's to modulate a single 4-65.
Yeah, yeah.. your thinking 'what overkill', but y'know... a single 833
in the final should only need a pair of 250w dissipation tubes in the
modulator, but no one can argue that a single 833, mod'ed by a pair
doesn't sound absolutely wonderful!
6.3v @ 3.5a? Got those transformers, too.
Actually, they want 6.0V, so drop the voltage to the primary or run
resistors in the primary or secondary circuits of the fil xfmr. One
trick is to use appropriate lengths of undersized wire to the
filaments (whatever length is necessary to drop the filament voltage
at the socket to 6.0 V).
Well, even better. I've got some 6.6 @ 18amp transformers. Reduce the
primary voltage down to 110 vs 120vac and that should bring the 6.6v
down to 6.0, or, as you say, insert some series resistance to drop the
voltage on the secnodary. Maybe even a small value resistor to drop
the 6 tenths of a volt, back to the center tap of the filament
transformer... there's lots of ways of doing it.
Good info! Thanks, Larry!
--
73 de W5OMR
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