John Miles said the following on 11/17/2007 09:06 PM: > Well, I bought the other Datum 9390 that was for sale at the time Mike > posted this message (eBay 260177272556), and it's certainly an impressive > box of stuff for $150. There is an Efratom Rb module, a couple of power > supplies, and a bunch of cards with a wirewrapped(!) back plane. > > I hooked up an antenna and it's reporting '1 USABLE SATELLITE' so far, so I > guess there's not much wrong with it if anything. The last-known GPS > location corresponds to "Cavium Networks HQ" in Google Earth, in Mountain > View, CA. The rubidium oscillator works and appears to be in calibration. > > The only fly in the ointment is the phase noise at the 10 MHz output: > http://www.thegleam.com/ke5fx/compare.gif > > Is -120 dBc/Hz par for the course for Efratom FRS-C rubidium modules, or is > there likely to be a problem with this one?
Yours is actually better than spec... my Efratom FRS-C manual says the spec is -70 at 1 Hz offset, -110 at 100 Hz, -130 at 1 kHz. The notation is a bit odd though -- it says "dBc/sqrt(Hz)". My understanding is that the compact telecom Rbs put FM on the reference as part of the lock mechanism; that makes the phase noise fairly ugly. John _______________________________________________ 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.
