Dick, many use the stock 1000pf cap. I do too, but it makes me quezy as
the RF current rating is being taxed or probably exceeded. That said, if
you need a new one a 200pf 15kv would be ideal if you can find one cheap
enough. Otherwise a Sprague et al rated at 15-20kV should be fine- lots of
NOS 680pf et al out there for $3-5 at hamfests. I have one homebrew 6m amp
using a single 7.5kv 200pf cap (same size as the 15kv so I have to
wonder...). In my last homebrew 6m amp I used a pair of 100pf 15kV in
parallel.
73 Dave
----- Original Message -----
From: "RICHARD SOLOMON" <w1ksz@q.com>
To: "Amplifier Reflector" <amps@contesting.com>
Sent: Thursday, May 28, 2009 12:31 AM
Subject: [Amps] Doorknob Caps Needed: Background
>
> Let me back up a tad on this. I am converting an SB-220 to 6 Meters.
>
>
>
> One of the questions I have is about the Plate Coupling Cap value. I see
>
> values of anywhere from 100 pF to 1,000 pF used. There must be some
>
> way to determine the appropriate value besides closing your eyes an
>
> picking one out of the box.
>
>
>
> I didn't find any specifics in the West Coast HB so unless I experiment
>
> with a bunch I am going to have to rely on what others have done.
>
>
>
> Maybe the answer is to use the one in the SB-220 ??
>
>
>
> Any thoughts,
>
>
>
> 73, Dick, W1KSZ
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>
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