[time-nuts] Need Help - Datum 9390 GPS Time Code &FrequencyGenerator

phil fortime at bellsouth.net
Tue Oct 7 05:00:19 UTC 2008

I've had three of those units and all three had different gps 
receiver/boards. Most as John said, are "plug and play', however, all I have 
seen require about 40 ma to be drawn by the antenna to eliminate the antenna 
error on the display after it boots up. Most of those high current antennas 
like the older Trimble's had about 42 db gain. I'm not saying that is the 
problem, but you did say "Signal Level Low".  Most of the antenna error 
problems can be tricked into thinking the antenna is there by paralleling a 
resistor on the antenna/input. (that dosen't solve your present no signal 

I had one "crap" out a few days ago where the receiver front-end gave up the 
ghost. Most of that vintage electronics loose capacitors with age, possibly 
that is the issue. I was also wondering if a newer receiver could be 
substituted/adapted like the trimble ace 2 or 3.

Oh, a side note, unless it was upgraded just prior to being obsoleted it 
will have the gps week rollover problem. Time and frequency will be fine but 
date and week will be wrong.


----- Original Message ----- 
From: "John Miles" <jmiles at pop.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Monday, October 06, 2008 10:19 PM
Subject: Re: [time-nuts] Need Help - Datum 9390 GPS Time Code 

> Sounds like you're doing everything right.  9390s are plug-and-play by
> nature, so I'd have to wonder if there's some front-end damage to the GPS
> receiver.
> -- john, KE5FX
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>> Behalf Of Myers, Charlie
>> Sent: Monday, October 06, 2008 6:59 PM
>> To: time-nuts at febo.com
>> Subject: [time-nuts] Need Help - Datum 9390 GPS Time Code &
>> FrequencyGenerator
>> Importance: High
>> I recently obtained a Datum model# 9390-52321 GPS Time Code & Frequency
>> Generator.  This unit has a Rubidium time base.
>>  I hooked the unit up to my Motorola GPS2000 GPS antenna (which is
>> mounted on the roof of my house) and powered the unit up, but I can't
>> seem to get the unit to see the satellites.  I keep getting the
>> following error message on the LCD display, "Signal Level Low" followed
>> by the status message, "GPS Time Not Acquired".
>> I checked the antenna and transmission line and they seem to be okay
>> because they operate my HP z3801A GPS time/frequency receiver just fine
>> and I get plenty of satellite signal level on the HP receiver.  I
>> checked the +5 volts on the antenna connector on the back of the Datum
>> unit and that measures correctly.
>> Does anyone have any ideas where to look or what other tests to perform
>> to isolate this problem?
>> Thanks for any assistance you can provide me.
>> Charlie Myers
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