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

[Chris Howard]

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.