Correct. David N1HAC
On 9/27/18 12:55 PM, Dave B via time-nuts wrote: > ... Because I'm sure I should be able to figure this out for myself! > > I have (as many of you do also) one of the venerable Trimble Thunderbolt > devices. No problem with that. All works fine, and is run 24/7, UPS > backup power and all... > > I also have (again, as many of you do...) a free running OCXO for 10MHz > used for "other" stuff etc. Also left running for long periods, but > only when I want to experiment with other stuff and don't want to > disturb what the TB is keeping sane.. > > Triggering a dual beam 'scope (Tek 465) from the TB on Ch1, and having > the output of the OCXO on Ch2, the resulting display on Ch2 of course > drifts in relation to the static waveform on Ch1. (Both nice sinusoids.) > > If I time how long it takes for the OCXO to drift through one full cycle > (co-incidence to co-incidence) relative to the TB on Ch1, how exactly do > I turn that time, and knowing the base frequency of the TB at 10MHz, > into a ppm discrepancy? > > "I think", that if for example, it takes 1 second to drift one cycle, > that works out at 0.1 ppm. If it takes 2 seconds, it's 0.05 ppm, if it > takes 5 seconds, it's 0.02 ppm etc. Is that correct? > > If not, please feel free to educate me! > > As I said, a silly question that I'm sure I would have answered myself a > few decades ago, but age and medication etc... > > Interestingly, after "a lot" of googling, I see that anything like this > using "analogue" or "CRT" scopes, has fallen off the radar and the > interweb, and some of the practices using digital oscilloscopes seem to > rely on the instrument itself to make the measurement, rather than from > "observation" and common sense. (That I seem to lack at times too!) > > But I did get diverted into reading up on some of the early history of > CRO's. > > Regards to All. > > Dave B. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.