Hi To that I would add - how long was it on power when measured? Does it run on power 24/7 at the club or is it power down 99% of the time? 10811’s (at least as much as other OCXO’s) “like” to be power on all the time. However using it one way and calibrating it another way may not be the best approach.
All this “fun” is one of the reasons for setting up a “lab standard” and piping it to all the gear rather than calibrating each item individually. With the Chinese packaged GPSDO’s coming in at < $100 delivered it is not a major investment. That kind of thing may or may not make any sense at all in this case. Bob > On Dec 27, 2019, at 8:02 AM, Tom Van Baak <t...@leapsecond.com> wrote: > > Hi Robert, > > If your 10811 10 MHz oscillator is off by 0.08 Hz after 20 years it's > equivalent to an average frequency drift rate of only 0.08/1e7/20/365, or > 1e-12/day. If so, you have an absolutely superb 10811; one that's 500x better > than spec. Congrats! Don't power it off, don't touch it, don't move it, don't > tilt it, don't sell it. > > Still, there are a lot of assumptions here: > > - Do you know how closely was it calibrated 20 years ago? > - Did anyone measure it once a month or even once a year since then? > - Do you have reason to believe the frequency drift rate is constant or > predictable? > - What's the environment been like (temperature, humidity, pressure)? > - How much do you trust your cheap China GPSDO? > - What does your 53131A counter say over gate times of 10 s or 100 s, and > over an entire day or week? > - Was this a one-time lucky measurement or is your 10811 really this good day > after day after day. > > Lots of questions. What I mean is that you may have one of the best 10811 > ever seen, or something's funny with the above assumptions. The nice thing > about a precise time & frequency hobby is that, without too much effort, you > can figure this out. > > Still, 0.08 Hz out of 10 MHz is 1e-8, or 0.01 ppm, or 10 ppb, so depending on > the accuracy that you need for the amateur radio club, it may be plenty good > enough as-is. > > /tvb > > > > On 12/26/2019 8:51 PM, Robert DiRosario wrote: >> I am trying to calibrate some equipment at the amateur radio club at work, >> and my stuff. We have an HP 5340A with a 10811 inside. It must have been >> upgraded at some point in the past, the display uses Nixie tubes. I >> calibrated it c2000 using a HP Cs standard. That lab and it's equipment are >> gone. :-( >> >> From ebay / China I got a simple GPSDO that uses a Trimble 57963 inside. I >> use the output of the 10811 in the 5340A to drive an HP 53131A. I then >> measured the 10 MHz output of the GPSDO using the HP 53131A and got >> 10,000,000.08 Hz. >> >> Assuming the GPSDO is correct, is 0.08 Hz drift over 20 years a reasonable >> amount of drift for an 10811? >> >> I have an HP Z3801A, once I get a power supply for it I can check the other >> GPSDO. >> >> Thanks >> >> Robert >> KA3ZYX >> >> _______________________________________________ >> 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. >> > > > _______________________________________________ > 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. _______________________________________________ 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.
