[Central-Electronics] CE20 oscillator drift

[Paul Kraemer]

I think I compensated the entire loop by placing the 20 vr dropping resistor 
in the 458 directly below the 1626. Never knew I had a drift problem
Can't believe we ever cared about hundred hz drifts. As long as everybody 
was within a wrist twist of the rx tuning---who cared.
Paul K0UYA
----- Original Message ----- 
From: "k6jek" <k6jek at comcast.net>
To: <central-electronics at mailman.qth.net>
Sent: Friday, August 26, 2011 5:42 PM
Subject: [Central-Electronics] CE20 oscillator drift


> Have any of you tackled the 9 MHz oscillator drift in the 20A?
>
> I measured it yesterday. At T+35 it was skidding along at 45 Hz every ten 
> minutes.  It was still moving about 25 Hz every ten minutes after 65 
> minutes of warm up. It settled down nicely after two hours having moved 
> about 300 Hz from power on +5 minutes.
>
> Today I tried keeping things cool. I installed one of those Weber 5U4 
> replacements instead of the real 5U4.  I placed a very slow fan on top of 
> the cabinet drawing out, a 220 Hz muffin plugged running on110.  This made 
> things worse.  The overall drift was less but it was still moving after 
> four hours.  I'd hoped it would stabilize at a lower temperature and do 
> that sooner.  No dice.  I guess all I did was slow down the oscillator 
> heating process.
>
> Incidentally, those Weber solid state rectifiers get plenty hot 
> themselves.  I'd guess there's a big resistor inside along with a couple 
> of diodes.
>
> My thoughts are turning to negative coefficient capacitors and even to 
> crystal ovens.  Either that or to heck with it.
>
> Jon, K6JEK
> ______________________________________________________________
> Central-Electronics mailing list
> Home: http://mailman.qth.net/mailman/listinfo/central-electronics
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Central-Electronics at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html