[time-nuts] getting a grip on 10811 drift (beginner-ishquestion)

[Azelio Boriani]

Unfortunately, experience is a lantern lighting the way already done... and
it takes months to forge a good sword: no one should break any sword.

On Fri, Nov 9, 2012 at 10:53 PM, Chris Howard <chris at elfpen.com> wrote:

>
> My perpetually drifting 10811 pretty quickly made it to the negative
> voltage rail on the control voltage.
>
> I was looking at the oscillator output with an O-scope and it looked
> pretty nasty.  My equipment is not so hot, so I first chalked that
> up to bad probes.  But I did some google work on that and found an
> old time-nuts message thread about the 10811 looking bad if the
> output impedance is bad.
>
> The VE2ZAZ board has provision for a 50 ohm resistor on the oscillator
> output.  I have one on the board but it is a little-bitty thing,
> maybe 1/8th of a watt?  Something I probably got from the guts of a VCR
> or whatnot.  Hmm.  So I put in a 1/4 watt 50 ohm resistor (like
> the parts list called for).  My working hypothesis is that the small
> resistor was changing impedance due to heat.
>
> I have reset the control voltage to center value and got the coarse
> trimmer all beautifully centered.  It's been running for about a day
> and I am hopeful that I've made a difference.  So far so good.
>
> While I was interrupting the flow of 10 Mhz, I also mapped out the
> control voltage and corresponding digital control value and an
> approximate frequency.
>
> You EE guys are probably snickering and will want to
> tear the epaulettes off my time-nuts coat and break my sword.
> What can I say.
>
>
>
>
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