[time-nuts] Coarse adjustment of PRS-10 with 5335A

Robert Darby bobdarby at triad.rr.com
Mon Sep 2 12:21:55 EDT 2013


This is a dumb question but why not let the PRS-10 set itself using the 
1PPS input and an appropriate time constant?

Thanks,
Bob Darby

On 9/2/2013 12:09 PM, Bob Camp wrote:
> Hi
>
> Ok, you are fine with the 10 MHz reading on the 5335 to get things "sort of close". Once you get past about 1.0x10^-10 you may want to switch over to a pps based approach. More or less:
>
> Fire up 5335 with pps from gps / gpsdo and from the PRS-10. (I'm assuming it's a GPSDO)
> Watch the reading for a few seconds, record the average and the time.
> Go have lunch / nap / beer / what ever.
> Check the time and the reading.
> Do the math
> Bump the PRS-10
> Step / repeat at the couple hour time interval for a day or so.
> Drop back to a couple days, check and (maybe) adjust.
> Drop back to once a week, check and (maybe) adjust.
>
> Note that the 5335 only has to be on while you are actually observing the pps. No need for the heat / wear and tear the rest of the time. Your pps needs to run all the time, but that's only a problem if there is a power outage.
>
> The advantage of doing it this way is you get both high resolution and averaging at the same time. Since there's pretty much nothing to set up (no computers / no GPIB) it's reasonably foolproof. Assuming that the 5335 is doing it's thing and that the GPSDO is good to roughly the same level:
>
> 3 hours is 10800 seconds
> your reading is good to 3 ns (2 on the GPSDO and 1 on the counter)
> you  get +/- 3.0x10^-9 at 1 second
> you get about +/- 3x10^-13 at 3 hours.
>
> Since the ADEV of the Rb is much better at the longer Tau's, the data you are using is probably a better bet than anything you can do in less time.
>
> Bob
>
> On Sep 2, 2013, at 9:20 AM, Paul <tic-toc at bodosom.net> wrote:
>
>>> If you are trying to measure frequency with the 5335 rather than pps signals
>> Ah, I was unclear.  I'm adjusting the 10MHz output.  It was pretty far
>> out when I got it.
>>
>> --
>> Paul
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