In a message dated 26/11/2010 23:31:32 GMT Standard Time, [email protected] writes:
Ahh. Very interesting explanation. So is it somewhat correct to assume (yes, I know) that for a stationary (non-mobile) environment, these extra sats don’t make much difference? This seems to be what the explanation is saying. Ok. So let me see. For a frequency standard for use in lab equipment, it appears that short term, phase noise and other sources of noise are the things to be concerned with to get better results. These seem to really be accomplished with a good oxco. However, if I want a very accurate time-of-day clock for long periods of time, then I need long term stability which is where the GPS comes in. Do I have this right? So if I want a really souped-up freq standard for my lab, then I should concentrate on finding the best oxco I can (which may be disciplined by the GPS or manually occasionally calibrated to GPS), and use the best power supply I can find. These seem to be what I should concentrate on rather than more channels. I do believe that I read some stuff on the internet that the HP GPS DO's do seem to have very good power supplies (or converters) which contribute to low spurs. So it seems the HP's do have a real advantage (not just the name). --------------- In searching for the best there is we may sometimes lost sight of what we were looking for to start with ..... old Scottish proverb I just made up:-) What gives "better" results so often depends on what you wish to achieve. You might not get the absolute minimum phase noise from something like a Thunderbolt, but then you might also have to ask if you need it. When it's working well, and some have been known not to in quite subtle ways, the HP Z3801A, the only HP unit I can speak for, is an excellent GPSDO. What you might not notice though without reading the very small print is that it can take two to three weeks to settle after being repowered for whatever reason. On the other hand, the Thunderbolt, in my experience anyway, is generally well settled in 15 to 30 minutes. Because the Thunderbolt is so widely available it seems as though it's can also be easily dismissed at times but don't underestimate it, it's an excellent GPSDO. I would recommend that you look for one of the Chineses sellers on Ebay offering T'bolts from no earlier than 2005 and with revision E software, fluke.l is one good exapmple, and go for that. There may well be an issue with the temperature sensor, much more in the archives on that, but replacements, if you really need one, cost pennies. Once you have that, and it's stabilised, you can either use it as it stands or use it to adjust your 10811 or whatever. For some time now I've tended to treat my Z3801As as interesting high quality museum pieces, whilst using three T'bolts as references/confidence generators. I then use those to calibrate the rubidium modules and 10811s that serve as my lab standards, which works well for me. regards Nigel GM8PZR _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
