[time-nuts] EFC info on Trimble 34310-T OXCO

Dave M dgminala at mediacombb.net
Sun Aug 24 16:14:12 EDT 2014


>
> Hi Dave,
>
> On 8/23/2014 3:51 PM, Dave M wrote:
>> Thanks for that suggestion, Ed.  After a bit of reading in the X72
>> Reference Guide, it appears that the X72 does have a 1PPS input.
>> That would be considerably easier than trying to interface the Rb
>> into the GPSDO.  Still trying to understand what the manual is
>> telling me. Next thing is to determine if my unit has that option
>> enabled (firmware option).  That will be a chore for after the
>> holiday... really busy next week.
>>
>> What would that (1PPS disciplining) do for me... in terms of
>> maintaining the Rb frequency accurately set?  Would it be as accurate
>> as having the Rb disciplined via the EFC input?
>
> It's kind of overkill, but by connecting the 1 PPS from the NTBW50AA
> to
> the X72, the X72 will be disciplined to the 1 PPS so the frequency
> will
> be accurate.  The question is how well will it be disciplined, i.e.
> what
> will the Allen Deviation graph look like.  I have a few X72 and SA-22c
> (X72's cousin), but none of them have that option.  I don't know of
> any
> published data on it.  Maybe you can tell us how well it performs.
>
> In general, I just don't see the point of disciplining a Rb standard
> to
> GPS.  I don't understand what will be gained by doing it.  I have a
> Z3801A and a Tbolt plus a free-running FRK as a house standard.  I
> occasionally compare the FRK to the Z3801A but the drift is so low
> (~1e-12 per month over 9 months) that I see no reason to link them.
>
> One exception that I recently discussed on another forum was a guy who
> lives in a ground floor, north-facing condo.  He might need to have a
> disciplined Rb standard due to poor GPS visibility.
>
> Ed
>

Sorry for forgetting to change the Subject line on my last post.

I see the futility of trying to integrate a Rb oscillator into a GPS 
receiver.  As it turns out, my X72 doesn't have the 1PPS input option 
enabled, so that's a moot point.  end result:  I now have a couple of GPSDOs 
and a Rb that I can use separately, as needed.  I would like to have a 
frequency comparator that can handle 10 MHz inputs natively without having 
to divide them down to 5 MHz.  I have a Fluke/Montronics model 103A 
Frequency Comparator, but its max frequency input is 5MHz.  I have a TADD-2 
divider board, but I want to build a two-channel divider board to dedicate 
to the Fluke comparator.  Which logic family is most suitable for such use; 
ALS, AC, etc.?  Low jitter would be the critical parameter?  I only need to 
divide by and 10, and maybe 100.

My original dream, and the impetus for this thread, was to have a frequency 
standard having the excellent short-term stability of the Rb, but have it 
disciplined to the GPS to maintain its long-term accuracy without having to 
correct the Rb manually.
My conclusion; it's now quite obvious that the old-school manual method is 
probably easiest and best.  I'll set the frequency on the Rb, watch its 
performance for a few months, and use it as the main frequency source for my 
bench.


Thanks for all the advice.

Dave M 





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