> Hello folks, > > i like to play the bad boy again: My claim is > > a) that for most of us a GPSD Rb is of little to no > use compared to a good GPSD xtal oscillator
Ulrich, That's a rather general statement, but I understand what you mean. Consider, instead of a bold general assertion which can be disproved with a single counter-example, a simple list of advantages of quartz vs. rubidium. Then let the user decide which is appropriate for their unique application. There's more to a GPSDO than its ADEV. For example, Warm-up time -- Many Rb will lock in 5 minutes, typically. Some Qz take much longer to get on-frequency from cold start. This can simplify the initial loop locking algorithm. Power consumption -- Probably Qz-based GPSDO have much lower power consumption than Rb. Physical size -- I would guess most Qz GPSDO are smaller than Rb GPSDO. One could argue that the Casio GPS wrist watches are a type of miniature GPSDO! Hold-over performance -- For mid- to long-term, Rb is vastly superior to Qz; most Rb have daily drift rates 100x better than Qz. Stand-along performance -- Without GPS lock, a free-running Rb can be trusted to be orders of magnitude more accurate than Qz. Environmental -- Is it the case that Rb is less sensitive than Qz to extreme environments? Cost -- As a rule, Qz-based GPSDO are cheaper than Rb. Phase noise -- I'd guess that Qz-based GPSDO could have better short-term stability and phase noise than Rb. Tuning range -- Could it be that Rb will run for many more years without coarse adjust than Qz? Lock indicator -- Most Rb give you a signal when frequency lock has been achieved. Mechanical sensitivity -- Rb GPSDO are much less sensitive to movement and shock than Qz. If you don't believe me watch what happens if you simply take your GPSDO and bump it, or turn it over on your desk. This is especially important during hold-over when no external correction is present. Lifetime -- Is the MTBF of Qz much longer than Rb due to fewer parts and simpler design? Surplus -- There are so many cheap telecom Rb out there it is near irresistible to make a GPSDO out of them. You get the idea; feel free to add the ones I missed. /tvb _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts