[time-nuts] Trimble Thunderbolt setup optimization and adding a10811 OCXO

[Arnold Tibus]

Don,

welcome in the boat.
You describe with other words what I am fighting against. 
There must be a logic behind which we did not find yet. 
I want to understand what is hidden behind all the setting parameters 
and find a way to get the 10811 running without degradation but 
just disciplining the OCXO drift away. 
But without knowing the logic behind and without a known reference 
a bit difficult...

Regards
Arnold

On Mon, 13 Jul 2009 13:15:29 -0700 (PDT), Don @ True-Cal wrote:

>Arnold,

>I have the same question as well as observations as yours. I have been working with both the TBolt and Fury connected to two different 10811s. With either the TBolt or Fury, I can't get the TC large enough to only provide a nudge to the EFC every few minutes. Both receivers get real unstable and cause large Freq and PPS swings with large TC numbers. It seems the EFC is providing many corrections per minute even with the TBOLT set to 300 secs. Anything larger than 300-500 sec. on the TBolt and EFCD=150 (don't know what the equates to in secs.) on the Fury will cause instability. I have better luck disabling desciplining on the TBolt or disconnecting the antenna on the Fury (no command to disable that I have found) when I need to do a Tau 0.1-10 sec. low jitter measurement.
> Regards...
>Don 




>________________________________
>From: Arnold Tibus <Arnold.Tibus at gmx.de>
>To: Discussion of precise time and frequency measurement <time-nuts at febo.com>; Tom Van Baak <tvb at leapsecond.com>
>Sent: Monday, July 13, 2009 1:56:56 PM
>Subject: Re: [time-nuts] Trimble Thunderbolt setup optimization and adding a10811 OCXO

>Tom,:

>>> Astonishing for me,
>>> I found that the 10811 does behave better in undisciplined 
>>> mode for a limited time:

>>This is to be expected. An undisciplined high-quality OCXO
>>like a 10811 will be hundreds or thousands of times better
>>than the raw output of a GPS receiver at short averaging
>>times. This is why a GPSDO exists; it allows the OCXO to
>>run almost free for minutes to hours but allows GPS to rule
>>for long-term.

>yes that is what I thought, but if I do observe correct, TB's 
>OCXO does not run at all free for minutes. With a time 
>constant of 360s the EFC and thePPS is surfing up and 
>down, why, I do not see the need to shift this OCXO within 
>2 minutes 80ppbs up and pps15ns as well - with this stable 
>oscillator....what is the driver, the SATs (I think not so)!

>Arnold