The thunderbolt is one of the best timing devices but not for frequency, if you want high resolution. Over time it is ok but high resolution short gate times and you see the frequency changes. They use the OCXO to correct for timing error and if you have a Tracor 527E you can see it. Also how else do you think they control the 1 pps. Bert Kehren In a message dated 4/26/2014 1:52:10 P.M. Eastern Daylight Time, [email protected] writes:
Magnus wrote: >The PRS-10 have a nice little trick in it, it stores the previous >OCXO steering value, so on power-up it sets the OCXO to this The PRS-10 has quite a number of nice tricks, in addition to particularly good engineering and high-quality construction of the basic physics package and support circuitry. The OP (and others) should not expect the same level of performance from $30-$100 ebay Rubidiums (LPRO, FRS, FE-56xx, etc., etc.). Very good to excellent OCXOs are available readily for $5 to $50. IMO, those should be the standard of comparison for any aspiring time nut. I'm not aware of any economy Rubidium that has close-in phase noise or low-to-medium-tau AVAR nearly as good as one of these very good OCXOs. As mentioned by others, some Ru may do better than a TCXO close in and at low tau. But so what? The TCXO should not be a time nut's standard of comparison as far as a lab standard is concerned. One quickly concludes that a good GPSDO, which includes a good OCXO, is the optimal solution for most time nuts. The OCXO has excellent stability with respect to close-in phase noise and low-to-medium-tau AVAR, and is disciplined by the GPS for excellent stability at longer tau. Probably the best turn-key solution is a Trimble Thunderbolt (although prices have risen in the last few years, so they are not the bargain they once were). Other, less expensive Trimble units that are also supported by the Lady Heather monitoring program are available on ebay, and are probably the best bet today for bargain-hunters. While I applaud the recent efforts to build simple DIY GPSDOs using inexpensive microcontrollers, from what I have seen so far most of them do not yet have the programming sophistication, particularly in the PLL loop filter and the houskeeping functions, to rival a good off-the-shelf GPSDO from a quality manufacturer. Final thought for specifying/designing/buying a GPSDO for time nuts purposes: Do not settle for a low-quality crystal oscillator (and especially not a TCXO). You will never achieve best performance at tau < about 100 seconds that way. Insist on a "10811-quality" OCXO (one of the many nice things about the Thunderbolt is that it has a very good OCXO). Best regards, Charles _______________________________________________ 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.
