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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