Hi > On Jan 15, 2015, at 4:56 AM, Andrea Baldoni <erm1ea...@ermione.com> wrote: > > On Mon, Jan 12, 2015 at 06:16:01PM -0500, Bob Camp wrote: > >> Actually it’s a bit worse than you might expect. >> The uncorrected sawtooth will give you about 20 ns of wander. At the one day >> level, GPS without some sort of ionosphere help (like a dual frequency >> receiver) will add another 10 ns or so to that. Net, your pps is spread over >> a 30 ns range. > > Hello Bob. > Thank you, now I have a better idea. > I understand that the NTP is completely ruled out and also between GPS there > is a strong difference. > >> With things like 5335’s running around for cheap prices, I would suggest >> doing this with a counter. You are going to spend a lot of days getting very >> much data. Your time’s got to be worth something …. > > Actually I own a Racal 1995 that should be better than the 5335 with its 1ns > single shot resolution. > However, I don't still own a GPSDO to reference the counter so how do you > suggest to use it?
Divide both of the things you are testing down to 1 pps. Trigger the start on one and the stop on the other. Read out the difference to the 1 or 2 ns resolution of the counter. That’s going to be ~ 100 X better than measurement with the rolling counter. Bob > I should use total A over B with the DUT in A and the PPS in B? > > Best regards, > Andrea Baldoni > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.