Hi The original patents on the MCXO are government property. One of the Ft. Monmouth guys came up with the fundamental / third overtone idea back in the 80's. Several (at least three) companies were licensed by the government to make the part.
Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Thursday, August 30, 2012 2:54 PM To: [email protected]; [email protected] Subject: Re: [time-nuts] oscillators There are some drawbacks to this type of SC-cut MCXO I would think, and it could possibly be replaced by a much higher performance Symmetricom CSAC, probably at a lower cost and higher availability: * Q-tech MCXO is ITAR controlled, CSAC is not * MCXO has 20ppb over temp stability, CSAC has 1ppb spec, typical units can be much lower than that. Our GPSTCXO has 75ppb over temp, not much more than the MCXO, but probably at 1/10th the cost. * The G-sensitivity of CSAC is at least 50x better than the MCXO (its so low, its very hard to measure) * Aging of MCXO is much higher (order of magnitude) * Symmetricom is a big player, Q-tech is relatively small and unknown * I remember that there are patents on the MCXO held by FEI? * Power consumption is very similar, future CSAC units will have much lower power than the MCXO. The MCXO does have lower phase noise, it's an SC-cut cyrstal after all. But with CSAC's now becoming available from multiple sources, why use an MCXO? bye, Said In a message dated 8/30/2012 10:35:56 Pacific Daylight Time, [email protected] writes: First, it has to have no activity dips over the full operating temperature range. OCXO crystals only have to work at the oven temperature. Activity dips, according to John Vig, are the reason whey they don't use mode B to sense temperature. Second, it has to be cut correctly so that the beat note between the fundamental times 3 and 3rd overtone modes is a useful indicator of temperature. _______________________________________________ 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.
