[time-nuts] Datum 9390 Rb phase noise

John Miles jmiles at pop.net
Sat Nov 17 21:06:29 EST 2007

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:

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?

-- john, KE5FX

> BTW, I just placed another of the 9390s on line last night, using the same
> output of the amp/splitter as the one that used to go to the 9390
> that died,
> and, this morning it is locked and showing both the right time
> and the right
> day of the year. This one came for less than $100 with shipping from ebay.
> It was sold as is, had a special connector on the rear for AC and another
> for DC, so, was sold as is. After finding a connector and wiring it up, it
> did not work. A little trouble shooting revealed a defective
> on/off switch.
> This one also has a Rubidium inside. Date code of most parts is 1994. This
> one has about 25 or so BNCs on the rear, so, just about every
> type of output
> is available. Not a bad investment. Here is the ebay URL for it in case
> anyone is interested. Regards - Mike
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320148228587


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