[time-nuts] LTE-Lite module

Bob Stewart bob at evoria.net
Mon Oct 20 20:03:41 EDT 2014

OK, Yahoo has done it to me again.  Sent to Tom direct and not to the list.  So, repeated here:

Hi Tom,

One of the biggest problems I've unwittingly faces is that of retrace.  I 
had seen the term used several times, but hadn't looked it up until last night.  As you can imagine, with a GPSDO under development I've had to 
remove power more than a few times to make hardware changes.  I think 
the next time power is down I'm going to try to rearrange things so that the OCXO is permanently powered and just the board gets switched.  But 
then again would big jumps in the EFC cause other problems that are 
almost as bad?  

There is just so much to learn to get this going; especially without either 
an engineering degree or experience in this field.  Bob Camp is 
definitely right that you have to put your time in - lots of it.

Bob - AE6RV

 From: Tom Van Baak <tvb at LeapSecond.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
Sent: Monday, October 20, 2014 6:42 PM
Subject: Re: [time-nuts] LTE-Lite module

To add to Bert's note...

Realize that for a GPSDO, (linear frequency) aging-per-day is irreverent, almost by definition. What matters is phase noise and short-term stability, neither of which you can possibly fix with disciplining against GPS. GPS takes care of the rest.

Long-term stability can be critical for non-GPS applications, which is why oscillators with daily aging rates in the -11's and -12's are so amazing.

Consider this: if you want to run your bench with a clean 10 MHz source, stable to 11 or 12 digits and accurate to 9 digits -- you may be much better off with a free-running, stand-alone OCXO with an aging rate down at 1e-11/day than using a GPSDO/TCXO. To maintain accuracy of your OCXO just re-tune your OCXO *once a year*. Aside from ADEV plots, this is another way to appreciate how amazing some OCXO are, any why many of us still troll eBay for high-stability, low-noise, low-drift quartz oscillators.


----- Original Message ----- 
From: "Bert Kehren via time-nuts" <time-nuts at febo.com>
To: <time-nuts at febo.com>
Sent: Monday, October 20, 2014 4:01 PM
Subject: Re: [time-nuts] LTE-Lite module

Allow me to clarify.
I started out with 7 MV 89 one of it a total loss. The remaining 6 after 3  
month +  burn in show better than 1 E-11 aging per day, 2 closer to 5 E-12. 
Only two have been tested for ADEV and are close to 1 E-12,  2X not 10  X.
Bert Kehren

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