----- Original Message -----
From: "Bill, W6WRT" <dezrat1242@yahoo.com>
To: <amps@contesting.com>
Sent: Monday, December 07, 2009 12:54 AM
Subject: Re: [Amps] TITAN II tuning and loading padder capacitors
> ORIGINAL MESSAGE:
>
> On Sun, 6 Dec 2009 14:30:38 -0500, "David J Windisch"
> <davidjw@cinci.rr.com>
> wrote:
>
>>Are these N750 capacitors suitable as padders in this r-f application?
>
> REPLY:
>
> A lot of manufacturers use N750 or similar caps and they do drift. If the
> drift
> isn't excessive, I'd ignore it. Does the power output actually change or
> are you
> seeing just the plate and grid readings changing?
>
> If you want to fix it , try finding either some NP0 ceramic or
> transmitting-rated mica capacitors. They are hard to find with high enough
> current ratings for legal limit amps, and they are expensive if bought
> new.
> Don't be tempted to use the little ones the size of postage stamps unless
> you
> parallel a bunch of them to spread the heat dissipation.
>
> 73, Bill W6WRT
Be careful with any mica cap as the older ones are prone to leakage. I
wouldnt use any without a leakage test of least at 500-600V.
The 12KV teflon disc caps are in wide use these days and seem quite stable
even at 2500W.
Carl
KM1H
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