[Amps] TITAN II tuning and loading padder capacitors

[Jim W7RY]

Where do you find those caps Carl?
Thanks
73
Jim W7RY

----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: <amps at contesting.com>
Sent: Monday, December 07, 2009 6:37 AM
Subject: Re: [Amps] TITAN II tuning and loading padder capacitors


>
> ----- Original Message ----- 
> From: "Bill, W6WRT" <dezrat1242 at yahoo.com>
> To: <amps at 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 at 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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