[time-nuts] Setting up PRS10 with M12+T GPS

Jerry Mulchin jmulchin at cox.net
Thu May 3 18:56:40 UTC 2012


Thanks to all that replied to my questions.
I have been off doing the suggestions offered and have found out some interesting
things about my unit.

Found out that the unit I have does not allow for certain parameters to be changed using
the command line. Argh!!!! Called SRS and talked with a guy named Dave, and he told me
that the unit I have based on Serial Number was originally sold to Symmetricom and they
required special settings for TO, TS and a few others that are "factory settable" only. What's
more, there is no way to upgrade the firmware for my unit as it is at least 12 years old. I've been
using this unit since 2007 as an un-disiplined unit. They want over $700 to upgrade the
unit if I send it back, and that is iffy. So I guess I'll live with it for now, and maybe look at
getting another unit with a much higher serial number or buy a new one at $1500.

Anyway, I dropped the PT time down to zero and started watching the TT values. TT values
were in the high 500 to 700 range which means the 1pps edges were not aligned very well.
I slowly started increasing the PT value, letting it settle out for a while, and the TT values
started dropping. I'm currently at PT=7 and the TT values are ranging from 999,999,987ns to
20 ns. This much change is probably due to the sawtooth nature of the 1PPS from the 
M12+T unit I'm guessing, as I don't have sawtooth correction implemented yet. I can adjust
the PP (Pulse Position) value from 0 to 999,999,999 ns, but I'm not sure that does anything
yet to help me. I'm still looking at this though.

I didn't ask the guy at SRS if there was a "backdoor" method to allow changing these
"factory only" settings, and he probably wouldn't have told me if there was. So does anyone
on the list know if this is possible?

I guess the bottom line is; while I can't adjust certain parameters like the manual suggests,
I do believe the PRS10 is locked to the 1PPS from my M12+T and tracking it. This is
clear from the data I'm seeing coming back from the PRS10, especially the TT values.

I will press on with the Sawtooth correction and get that working.

Thanks again for the help.

Jerry Mulchin


At 12:46 PM 5/2/2012, Jerry Mulchin wrote:
>I need some guidance from the collective.
>
>I just finished rebuilding my PRS10 lab standard and it is now using a M12+T GPS module.
>I have completed my site survey and it is now in "hold position mode", TRAIM is enabled
>with 500ns alarm setting and the 1PPS is enabled during non-TRAIM alarm conditions.
>
>The PRS10 is set for default 1PPS steering, but all of the other parameters are just as 
>I received the unit 5 years ago.
>
>My questions are these;
>
>1.) Should I reset the PRS10 to its Default settings or just adjust selected parameters to
>align the unit for proper operation with the M12+T unit? And if that is the case, what parameters
>need adjusting?
>
>2.) Are there any special settings, other than what WinOncore sets, that I should make to the
>M12+T unit?
>
>3.) After all this is completed, how do I know that the PRS10 is properly tracking GPS and
>maintaining frequency accurately? I don't have a Cesium reference, but I do have an un-disiplined
>LPRO-101, but I don't think that really helps me determine frequency accuracy.
>
>I will be adding the sawtooth correction eventually to the M12+T 1PPS output, but observed
>negative sawtooth with WinOncore shows +/- 14ns changes with some bridging occasionally.
>
>While I don't ever want to claim NIST traceability, I would like to be a close as possible, and I
>guess that is the bottom line need here. So what else do I need to do to get as close as possible?
>
>Thanks for any help.
>
>
>
>
>Jerry Mulchin
>
>
>
>_______________________________________________
>time-nuts mailing list -- time-nuts at febo.com
>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>and follow the instructions there.


Jerry Mulchin





More information about the time-nuts mailing list