[time-nuts] EFC info on Trimble 34310-T OXCO
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
> the X72, the X72 will be disciplined to the 1 PPS so the frequency
> be accurate. The question is how well will it be disciplined, i.e.
> 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
> 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
> 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.
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
Thanks for all the advice.
More information about the time-nuts