I'm not sure if there is a reason counters don't let you digitally calibrate beyond that, the 10 MHz ref out on the rear panel would still be out of cal.
On Fri, Nov 4, 2016 at 1:48 PM, Bob Camp <[email protected]> wrote: > Hi > > The only practical way to set the 10811 or 10544 is with a >= 10 turn pot > on the EFC. I > never have worked out just why there are so many instruments that don’t > have a pot on > the EFC. > > Bob > > > On Nov 4, 2016, at 11:35 AM, Peter Reilley <[email protected]> > wrote: > > > > I gave up on trying to use the GPS 1 PPS signal to calibrate the 10 MHz > OCXO's that > > I have. The reason that others have pointed out is that the > uncorrected 1 PPS > > signal from the GPS is has just a little too much a jitter to use it for > calibration > > with your eye using a scope. If it were sawtooth corrected then it > would be better > > but you really need a GPS disciplined oscillator. > > > > Not to be outdone, I brought out a rubidium oscillator that I had put > away because > > it did not appear to work properly. It only put out a 1 PPS signal and > nothing else. > > I compared that with the GPS PPS and could get a good comparison on the > scope. > > The rubidium drifted about 40 nS over 12 hours. So it seemed to be > good. > > > > With that I could adjust the OCXO's in my 5370's. The spec for the HP > 5370B with > > a HP 10811 OCXO is better than 1 X 10^-10 RMS for 1 sec average. That > is, it should > > take more than 1,000 seconds for one 10 MHz wave to shift by 360 > degrees. That > > is very hard to do using the screw adjustment in the OCXO. Even the > slightest > > movement possible will cause a frequency change greater that is > spec'ed. How > > do cal labs do it? > > > > My HP 5370A has a 10544 OCXO which is spec'ed for short term stability of > > better than 1 X 10^11 for 1 second. Even better than the 5370B! The > adjustment > > screw is much coarser and it is not possible to get any better than a > few seconds for > > one cycle phase shift of the 10 MHz OCXO against the standard. It > seems that I can't > > get even close to the spec. > > > > These have been running for a few days. It that enough? > > > > Pete. > > > > > > > > On 11/3/2016 8:20 AM, Peter Reilley wrote: > >> I am the proverbial man with too many clocks and I don't know what time > it is. > >> To correct this situation I have decided to calibrate everything. > >> > >> I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO > option. I also > >> have some TCXO modules. I figured that I would calibrate them against > my Trimble > >> Resolution T GPS receiver. > >> > >> I put the 1 PPS signal in one channel of my scope and one of the 10 MHz > TCXO > >> signals in the other channel and look at the phase relationship. The > TCXO's are > >> already close enough that I should not be out by more than a fraction > of a waveform. > >> I understand that I have to deal with the 1 PPS without sawtooth > correction. > >> > >> I expected to see the 10 MHz signal bounce around but not move more > than 1/2 > >> of a wave length. Instead I see the 10 MHz waveform appear steady for > a few seconds > >> then jump a significant portion of the wave. The jump is too much to > be confident > >> that I have not slipped one cycle. > >> > >> Can I do what I am trying to do or am I missing something? > >> > >> Pete. > >> > >> _______________________________________________ > >> time-nuts mailing list -- [email protected] > >> To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > >> and follow the instructions there. > >> > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
