[time-nuts] Trimble Thunderbolt setup optimization and addinga10811 OCXO

[Don @ True-Cal]

John,

Yes, I have changed the gain to exactly your suggested -0.2 V/Hz and I have experimented with the damping from .5 to 3 and I'm currently using 1.00. Things certainly change with various damping and TC settings but not nearly as slow and subtel as I would like to see for an oscillator like the 10811. On the Fury I am using DACG=250, EFCS=.8, EFCD=80 and PhaseCO=12 (favoring freq stability for 10MHz reference). On both configurations I typically see 3.1 to 3.3 nSec standard deviation so still much better than a Z3801.
 Regards...
Don 




________________________________
From: John Miles <jmiles at pop.net>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Monday, July 13, 2009 3:32:37 PM
Subject: Re: [time-nuts] Trimble Thunderbolt setup optimization and addinga10811 OCXO

What are you using for the Kvco constant with your 10811-based Thunderbolt?
If you don't back it down to -0.2 V/Hz, the loop's damping factor will be
very wrong, which might confuse the firmware.  Check the Kvco, and also do a
factory reset after changing the OCXO to make sure it forgets anything it
might be remembering about the OEM part.  (You might try that, too, Arnold.)

-- john, KE5FX

> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of Don @ True-Cal
> Sent: Monday, July 13, 2009 1:15 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Trimble Thunderbolt setup optimization and
> addinga10811 OCXO
>
>
> 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
>
>
>
>


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