[Central-Electronics] 10B Mod

[Jim Candela]

Colin,

    A while back I tried 4 different 9mc CE OEM crystals in the same 20A. I
plotted the 9.xxx Mhz frequency every 15 minutes up to 2 hours from a cold
start. No two were alike (not even close), and I picked the best of the lot.
My next move was going to get a modern crystal and try that. I was also
looking at some crystal ovens. I never moved forward on this.

   I think that temperature compensation might help, but as you know, that
is a long tedious road to go down. I might try that too. Thanks for the
advice. BTW, the X-Lock stabilizer will also work with a crystal VFO, but
the application seems silly.

http://www.cumbriadesigns.co.uk/x-lock.htm
http://pages.prodigy.net/jcandela/Band%20Hopper/

Regards,
Jim
WD5JKO

----- Original Message ----- 
From: "k7fm" <k7fm at teleport.com>
To: "Jim Candela" <jcandela at prodigy.net>; 
<central-electronics at mailman.qth.net>
Sent: Monday, November 09, 2009 9:06 PM
Subject: Re: [Central-Electronics] 10B Mod


> Hi Jim:
>
> A few years ago, I built a pocket sized transceiver using a voltage tuned
> vfo.  It drifted badly and needed temperature compensation.  Having
> compensated vfos many years ago with few instruments, I wanted to make 
> this
> attempt as painless as possible.
>
> So, I dragged out a drawer of small capacitors (including temperature
> compensating caps), my wife's hair dryer, a digital capacitance meter, a
> frequency meter and a infrared temperature probe.  First, I calibrated the
> drift of each capacitor.  Then, I applied the hair dryer to the vfo
> monitoring the frequency.  You can do the same thing with the crystal
> oscillator in the CE.  It will be easy to see if it is the crystal or the
> circuit.  If it is the circuit, temperature compensation is painless.  By
> the way, silver mica caps can be useful, but they are all different in
> drift.
>
> 73,  Colin
>
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