[time-nuts] LTE-Lite module and the pendulum...
SAIDJACK at aol.com
SAIDJACK at aol.com
Tue Oct 21 18:38:30 EDT 2014
those old Vectrons can be tricky. I had a 100MHz unit in my DTS-2070 and
it could not be adjusted to 100MHz anymore, it had out-aged its trim
capacitor. I threw it away I think, and replaced it with something more modern.
My initial point was that your trim cap problem is very similar to what the
loop is experiencing on oscillators that have an EFC hysteresis. There is
not a single vendor in the world that I know of that specifies this EFC
hysterisis, and this and the retrace of the crystal over the first couple of
hours are two extremely important parameters as they can cause significant
errors in GPSDOs.
In a message dated 10/21/2014 15:10:09 Pacific Daylight Time, biwa at att.net
The DATUM 9390's I have came from the Sieko pager watch project that
I was involved in back in the mid to late 90's. As I recall, even
when the DATUM clocks were new we'd have to adjust the oscillators
periodically to keep them within lock range. The center of the DAC
was around 27000 and they'd wander about 10000 plus or minus. They'd
sometimes wander out of lock at plus or minus about 15000 and one of
us would have to make a trip to some transmitter site to re-set the
clock and re-center the Vectron module. The adjustment was
accessible through a hole in the back of the clock. As I recall, you
could give the oscillator a half turn one way or the other without
causing too much distress to the clock. This held true with my two
units until the one oscillator developed the adjustment problem. Not
knowing what was really inside the Vectron, I attributed the problem
to a defective or cracked piston capacitor. The adjustment certainly
had the feel of a piston capacitor.
Since I made the modifications I described, the DAC sits within about
10 of 27450, and that's where my units are happy. By the way, I've
got two 1.5 KVA UPS's in my shoppe, one for each clock. They'll run
for a long time on those.
>From: Said Jackson <saidjack at aol.com>
>Subject: Re: [time-nuts] LTE-Lite module and the pendulum...
>Great insight thanks. You nailed it: out with the old oscillator and
>in with one that doesn't have that problem.
>Btw the mechanical tuning issue you mentioned is essentially the
>same exact problem: even the slightest turn will make the frequency
>jump too high or too low. It can drive you (and the loop) crazy
>trying to get it on-frequency.
Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
biwa at att.net
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