Gentlemen:
A couple parts questions for a small home-brew (2x) GI-7B triode hf amp
project I'm thinking about, please???
<1> Plate Bypass Capacitor
I've noticed values ranging from 1000pf up to 5000pf (2 x 2500pf) for
the Plate Bypass Capacitor in several amp designs... This works out to
a reactance of from 88.42 ohms at 1.8-MHz for 1000pf, to 17.68 ohms for
5000pf...
What is the best value for this bypass capacitor or does it depend on
which tube(s) you're using and all of the 'network' impedances you're
working with...
<2> Plate Bypass Capacitor
What types of capacitors can I use for the Plate Bypass Capacitor???
I've seen door knob ceramics as well as disc ceramics being used... I
noticed in the 4CX1600B project in my 2001 Handbook that the author
specifies two 2500pf 10kv ceramic door knobs, Newark #46F5253, but when
I looked up that Newark part it was a 2500pf 10kv disc ceramic (z5u)...
Is this another typo' in that particular article???
Anyone have a good source for 2000pf 10kv door knob z5u ceramic parts???
<3> Plate RF Choke
I noticed in that same 4CX1600B project in the handbook that the author
purchased a Plate RF Choke from Command Technologies... I'd like to run
this amplifier on 160 through 10, including WARC bands, and I'd like to
make sure the choke I end up with isn't resonant near any of those
frequencies... Any recommendations, sources, prices???
<4> Filament Choke
Hopefully there's nothing real exotic here... Two GI-7B tube filaments
will run 12.6vac at 4.0amps... I suspect a bifilar wound choke is the
best way to go and if I could get one designed for 5.0 or 6.0 amps,
instead of 30.0 amps (grin), I suspect it would be physically much
smaller than a 30.0 amp choke... Recommendations, sources, prices???
Toroidal???
---------------
I'm sure I'll have plenty of questions if I decide to start the
project...
I'm thinking about a custom Hypersil transformer with 820vac @ 1.0amp
CCS for the plate supply (doubler)... I looked at 1640vac @ 0.5amp but
the transformer ends up being quite a bit larger for the same VA
rating... Is this because of the voltage breakdown spec' of the
transformer windings, or something like that???
I ordered tubes (they're "cheap") and I'm anxious to start machining
sockets... Though, I'm still not certain about starting the full-blown
project...
I apologize for the long-winded note and I appreciate the collective
wisdom represented here on "the list"...
Very 73, Mike - K8LH (Westland, MI)...
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