Hi One hertz at 20 MHz is indeed 50 ppb. On a practical basis, that's as close as you are likely to get in terms of carrier accuracy over HF radio.
To do better, you would need to go to the time domain. Generate a tick off of your oscillator(s) and compare it to the time tick on the radio. Compared over a time span of days you can improve your accuracy. Bob On Sep 26, 2013, at 9:24 PM, Bob Albert <bob91...@yahoo.com> wrote: > This is off topic but I'm unsure how to do it properly. > > I am trying to 'discipline' a couple of sources. I zero beat with 20 MHz WWV > but can't tell the difference between fading and the beat, so I am stuck in > the vicinity of 1 Hz possible error. That's 50 ppb I think. > > What can I do to take the next step to bring the oscillators in closer > agreement? I am not ready to go GPS or buy a rubidium standard. > > > Bob > > > > ________________________________ > From: Bob Stewart <b...@evoria.net> > To: Discussion of precise time and frequency measurement <time-nuts@febo.com> > Sent: Thursday, September 26, 2013 6:13 PM > Subject: Re: [time-nuts] Shielding a DAC line > > > Hi Bob, > > I should have mentioned that I added a new 5MHz output, and the coax ran > within 1/8" of the single DAC wire going to the OCXO. I don't think anything > else changed, but of course there could be some flake of something on the DAC > line that I missed. I put on the RG-174 and I see that it's still locking > high. I suppose it could be just that it was a long power cycle to the > oscillator. Come to think of it, this thing does like to move to a new > voltage sometimes when I have it off to mess with something. So, maybe it's > just the oscillator being cranky. I haven't had it off for more than just a > few seconds in a long time. If I weren't in test and development mode where > anomalies are good, I think I'd put the old one back in. > > Thanks as always, > > Bob > > > > > >> ________________________________ >> From: Bob Camp <li...@rtty.us> >> To: Discussion of precise time and frequency measurement >> <time-nuts@febo.com> >> Sent: Thursday, September 26, 2013 7:54 PM >> Subject: Re: [time-nuts] Shielding a DAC line >> >> >> Hi >> >> I suspect that you have a ground offset between the OCXO's ground return and >> the DAC's ground reference. The signal *should* be DC, Shielding it won't >> hurt, but it really should not help much. If anything is an issue a simple >> R/C filter at the OCXO pin should nuke it better than coax will. >> >> Bob >> >> On Sep 26, 2013, at 8:09 PM, Bob Stewart <b...@evoria.net> wrote: >> >>> I made some minor hardware changes to my GPSDO today and I see that it's >>> locked to a new DAC voltage about 21mV higher. So, I was wondering about >>> shielding the short run to the OCXO. I have immediately available RG-174 >>> and I'm putting that in. But, should this be some sort of steel shelled >>> semi-rigid coax? Maybe it's a dumb question, but I thought I'd ask. >>> >>> Bob - AE6RV >>> _______________________________________________ >>> 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. >> >> >> > _______________________________________________ > 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. _______________________________________________ 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.
