Hi Not so simple decoder ring:
0 to 24 hours = use an auction site double oven OCXO ($50). 1 hour to a few days = use an auction site LPRO (or similar) rubidium ($50). 1 hour to forever = use a TBolt (or similar) made after 2001, but before 2005($100). The gotcha with any of the GPS devices is that they also do ionosphere measurements. Depending on just how crazy you are getting, the changes may impact both a GPSDO and your data at the same time. To get around the "correlation" affect, you would need to go to either a stand alone Cesium standard ($X,000) or a hydrogen maser ($XX,000). If you are looking for fast changing effects, then either the maser or the OCXO are the way to do it. Their short term stability is what you are after. Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Peter Vince Sent: Wednesday, September 22, 2010 9:27 AM To: [email protected]; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] [qs1r] Looking for good, cheap, external reference Hello Lester, To expand on Bob's message a little, do you need medium to long-term accuracy (for a frequency counter reference for example), or something that is both accurate AND has low phase noise, suitable for multiplying up to GigaHertz, say, for communications? Particularly if the latter, does the absolute frequency have to be accurate, or would a knowledge of the offset be adequate? If the latter, you could use a nice quiet OCXO, and use John's suggested Thunderbolt as a reference to your counter to determine the error. In any case, for private use there is no need to spend anything like $8000, lots of Rubidiums can be found on ebay for under a tenth of that. There is a lot of experience on this list with the Thunderbolt GPSDOs mentioned by John, and the complete kits offered on ebay make it an easy way to get an excellent reference. John, unless I am going mad, the ADEV plots for both auctions you mentioned look the same - maybe the bad one has been replaced since you posted your message? Regards, Peter _______________________________________________ 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. _______________________________________________ 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.
