[time-nuts] LTE-Lite module and the pendulum...

SAIDJACK at aol.com SAIDJACK at aol.com
Tue Oct 21 18:38:30 EDT 2014


Burt,
 
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.
 
bye,
Said
 
 
In a message dated 10/21/2014 15:10:09 Pacific Daylight Time, biwa at att.net  
writes:

Said,

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.

Burt



>From: Said Jackson  <saidjack at aol.com>
>
>Subject: Re: [time-nuts] LTE-Lite  module and the pendulum...
>
>
>Burt,
>
>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.
>
>Bye,
>Said

Burt I. Weiner  Associates
Broadcast Technical Services
Glendale, California   U.S.A.
biwa at att.net
www.biwa.cc
K6OQK  

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