From: "John Miles" jmiles@pop.net
Subject: [time-nuts] Datum 9390 Rb phase noise
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Message-ID: PKEGJHPHLLBACEOICCBJIEPGCKAB.jmiles@pop.net
Content-Type: text/plain; charset="us-ascii"

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?

-- john, KE5FX

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
Behalf Of Burt I. Weiner
Sent: Sunday, November 18, 2007 11:11 AM
To: time-nuts@febo.com
Subject: [time-nuts] DATUM GPS Thingies...

There is a master reset in the units that should be done when moving
the units any considerable distance.  It will eventually find itself
but takes considerably longer if you don't do the reset.  Without
doing that it's trying to go by it's last collected almanac.  On my
units it's a matter of turning the unit off off, flipping a dip
switch, turning it on and waiting for a message to tell you to turn
the power off and put the switch back.  After that it will start
collecting birds within a very few minutes and probably have them all
within about 15 minutes.

Burt, K6OQK

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
Behalf Of Burt I. Weiner
Sent: Sunday, November 18, 2007 11:11 AM
To: time-nuts@febo.com
Subject: [time-nuts] DATUM GPS Thingies...

There is a master reset in the units that should be done when moving
the units any considerable distance.  It will eventually find itself
but takes considerably longer if you don't do the reset.  Without
doing that it's trying to go by it's last collected almanac.  On my
units it's a matter of turning the unit off off, flipping a dip
switch, turning it on and waiting for a message to tell you to turn
the power off and put the switch back.  After that it will start
collecting birds within a very few minutes and probably have them all
within about 15 minutes.

Burt, K6OQK

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
Behalf Of Rob Kimberley
Sent: Sunday, November 18, 2007 11:51 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] DATUM GPS Thingies...

John,

What's the model number?

Rob Kimberley

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of John Miles
Sent: 18 November 2007 19:14
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] DATUM GPS Thingies...

That's good to know.  Are there any manuals/schematics or other documents
available for these?

-- john, KE5FX

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
Behalf Of Rob Kimberley
Sent: Sunday, November 18, 2007 11:51 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] DATUM GPS Thingies...

John,

What's the model number?

Rob Kimberley

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of John Miles
Sent: 18 November 2007 19:14
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] DATUM GPS Thingies...

That's good to know.  Are there any manuals/schematics or other documents
available for these?

-- john, KE5FX

Thanks for checking.  They seem to have been common enough over the last
couple decades, but there is no actual documentation that I can find...