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Discussion of precise time and frequency measurement

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Why is holdover LED on HP 58503A not lit, when GPS lock is unlit too?

BC
Bob Camp
Tue, Dec 20, 2016 12:18 PM

Hi

On Dec 19, 2016, at 9:30 PM, Charles Steinmetz csteinmetz@yandex.com wrote:

David wrote:

This does appear now to be working - see below. I'm not exactly sure what
was the secret to getting this to work, but the above procedure seemed ok.

Time.  It is not at all unusual for a 58503A that has no almanac (or an out-of-date almanac) to take several days to achieve disciplined operation (and much longer for the OCXO to fully stabilize).  You may get lucky and find that it happens faster, but don't count on it.  FWIW, HP GPSDOs often take longer than others to initialize.

Everyone, please remember -- GPSDOs can take significant time to re-initialize.  No need to post about what may be wrong until at least 3 days of continuous running after powering on.  Chill.

Same with respect to crystal oscillators settling to low drift rates. No need to worry about drift (retrace) for at least a month (sometimes 6 or even 12 or 24 months) of continuous running after powering on.

Honestly, the best thing to do is turn it on and forget about it for 3 days (GPSDO) or 1 month (crystal oscillator).  DO NOT observe it (log it, if you feel the need, and don't look at the log until after the 3/30 days).

….. and that’s several days with constant access to satellites (> 6 sats at all times). If your antenna location is “challenged” you can multiply the time required by some factor like 3 or 5 or …
This is why some of us spend a lot of time talking about the importance of antenna location on these boxes.

Bob

Precise time and frequency require patience!

Best regards,

Charles


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Hi > On Dec 19, 2016, at 9:30 PM, Charles Steinmetz <csteinmetz@yandex.com> wrote: > > David wrote: > >> This does appear now to be working - see below. I'm not exactly sure what >> was the secret to getting this to work, but the above procedure seemed ok. > > Time. It is not at all unusual for a 58503A that has no almanac (or an out-of-date almanac) to take several days to achieve disciplined operation (and much longer for the OCXO to fully stabilize). You may get lucky and find that it happens faster, but don't count on it. FWIW, HP GPSDOs often take longer than others to initialize. > > Everyone, please remember -- GPSDOs can take significant time to re-initialize. No need to post about what may be wrong until at least 3 days of continuous running after powering on. Chill. > > Same with respect to crystal oscillators settling to low drift rates. No need to worry about drift (retrace) for at least a month (sometimes 6 or even 12 or 24 months) of continuous running after powering on. > > Honestly, the best thing to do is turn it on and forget about it for 3 days (GPSDO) or 1 month (crystal oscillator). DO NOT observe it (log it, if you feel the need, and don't look at the log until after the 3/30 days). ….. and that’s several days with constant access to satellites (> 6 sats at all times). If your antenna location is “challenged” you can multiply the time required by some factor like 3 or 5 or … This is why some of us spend a lot of time talking about the importance of antenna location on these boxes. Bob > > Precise time and frequency require patience! > > Best regards, > > Charles > > > _______________________________________________ > 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.