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

[Don @ True-Cal]

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



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