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

Burt I. Weiner biwa at att.net
Tue Oct 21 16:19:00 EDT 2014


I'm not sure if you're referring to my comment about the Vectron VCXO 
jumping when I tried to adjust it or some other part of the 
discussion.  I was definitely referring to adjusting the screw on the 
side of the Vectron VCXO that I believe is a piston capacitor.  I 
suppose it could be a 10-turn trimpot.



>From: SAIDJACK at aol.com
>To: time-nuts at febo.com
>Subject: Re: [time-nuts] LTE-Lite module and the pendulum...
>
>
>Hi John,
>
>while I can't tell you which vendors are affected and which are not (Its
>like asking an angler for his secret angling spot :), I can say that most low
>  cost TCXOs exhibit this behavior, and are thus not really suitable for
>GPSDOs.
>
>
>The ones we used on the LTE-Lite are quite good and do not  exhibit this
>behavior. They are also 10x more expensive than the lost cost TCXOs  in the
>exact same package that are typically used in non-critical  applications.
>
>
>So far none of the quite reputable TCXO and OCXO vendors that I contacted
>about the problem can explain the behavior to me, like I said they were not
>even  aware of the issue and had no way to test for it, and I had to prove
>it to them  by sending our units to them so they can see the issue for
>themselves.
>
>Bye,
>Said
>
>
>In a message dated 10/21/2014 11:51:28 Pacific Daylight Time, john at miles.io
>  writes:
>
> >  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.
>
>Whenever I've seen this behavior, it has always been  caused by uncertainty
>or "quantization" on the part of the trimpot's wiper,  rather than anything
>that could be blamed on the varactor.  What would be  a good example of a
>TCXO or OCXO model that exhibits EFC hysteresis?  I  don't immediately
>understand what could cause this phenomenon, and I'd like 
>to  reproduce it here to
>see what's happening.
>
>-- john, KE5FX
>Miles  Design  LLC

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



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