[Hammarlund] Old Hammarlunds

[Carl]

The old rule of thumb is to start with a TC cap that is 10% the value of the 
variable then start your plots. You might be just fine with a smaller TC but 
a bit more C

A Google turns up several leads under  "temperature compensating capacitor" 
including a few good choices at $$N

Carl
KM1H


----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: <Hammarlund at mailman.qth.net>
Sent: Monday, April 11, 2011 7:33 PM
Subject: Re: [Hammarlund] Old Hammarlunds


> On 9 Apr 2011 at 15:44, Chuck McGregor wrote:
>
>> There was an earlier note on temperature compensating the SP-200
>> printed in QST for Feb 57, page 58.
>
> That amounts to adding only 3.3 pfd worth of TC capacitor with "as high
> negative coefficient of compensation as available" connected in parallel 
> with
> the oscillator tuning cap, then realign.
>
> Supposedly, this cut the drift down from well over 50 Khz, to 200 CPS.
>
> Sounds simple enough.
>
> Anyone know where one can get some negative 750 PPM, or 1500 PPM, TC
> caps?
>
> Ken Gordon W7EKB
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