2 ms·
The rise of GPS clocks has really killed the commercial market for cesium beam clocks-- the 5071 is a design over twenty five years old. It's a fine piece of
by nullc 5y ago
The rise of GPS clocks has really killed the commercial market for cesium beam clocks-- the 5071 is a design over twenty five years old. It's a fine piece of engineering (I have three, two I obtained broken and repaired) but its age is starting to show, including the fact that it is phenomenally expensive to get replacement tubes for (the tubes are limited life).
Similar is true for rubidium standards, though there are some somewhat more modern models-- though since they aren't primary standards most places that use them will still use GPS to keep them on frequency. A primary standard like a 5071 can internally compensate for every major systematic effect and so they can autonomously derive the second without external calibration. Telecom rb's can't self-calibrate for their gas cell pressure.
All this has lead to a worrisome dependence on GPS just as a precise source of frequency.
Hopefully in the long run we'll see single chip optical clocks with GPS-clock beating performance at competitive prices-- if they got even close to GPS they would rapidly displace it, as the need to put up an antenna for GPS is a real nuisance, and GPS jammers are a sadly too common source of trouble.
- wbl 5y agoIt's a pain to get the top of second calibrated on a ceasium beam clock.
- nullc 5y agoWho doesn't like taking a road trip to Boulder Colorado? :) The 5071a even has internal batteries.
- schoen 5y agoI know the NIST Time and Frequency division is based there, but what would you do in person once you got there? Do they have a service of some kind to help synchronize things in person for visitors?
- deleted 5y ago[deleted]
- nullc 5y agoPrior to the widespread use two way satellite time transfer (and secondarily GPS) for this purpose ( https://www.microsemi.com/document-portal/doc_view/133433-working-application-of-twstt-for-high-precision-remote-synchronization https://www.microsemi.com/document-portal/doc_view/133433-wo... )-- taking an atomic clock on a road trip was the standard way to obtain the second: https://ntrs.nasa.gov/api/citations/19820012622/downloads/19820012622.pdf https://ntrs.nasa.gov/api/citations/19820012622/downloads/19... There were even more portable units built specifically for this time transfer purpose. I don't think NIST has a regular service for this anymore, but since they do offer a host of calibration and verification services, I'd be surprised if you couldn't road trip a clock to obtain the second... at least for a price. I've seen some publications on transportable optical clocks in recent years, which I assume are motivated by validating newer higher precision TWSTT and fiber time transfer techniques.
- schoen 5y agoWow, that's amazing! Thanks.