[time-nuts] Datum receiver date and other issues...

Burt I. Weiner biwa at earthlink.net
Sun Nov 11 12:13:04 EST 2007

There was a software update for the Datum receivers that came out 
several years ago.  As I recall the cost of the update was around 
$500.00.  If you didn't add this update the date would be wrong but 
that's all.  Using it for a frequency reference only, the date itself 
is not important.  My two receiver had the update added by the 
previous owner.  In 5 years I may have looked at the date once.  Maybe twice.

I know that in in the OCXO version, if the receiver should unlock but 
still shows a signal or "tracking" the problem is usually due to a 
DAC number outside of the desired range.  It should be about 
37000.  It's usually just a matter of adjusting the oscillator 
frequency to bring the DAC number back within range.  As you look at 
the receiver from the rear, the adjustment is behind a covered screw, 
like most devices of this type.  Clockwise will raise the DAC number 
and CCW will lower it.  It may only take about one-eighth turn - 
depending on the oscillator.  I try and keep mine within about +/- 
5000 of the 37000.

For what it may be worth, a trick I found when there was interference 
from a nearby lower frequency transmitter was to put the GPS receive 
antenna inside and at the bottom of the equivalent of a two pound 
coffee can.  Be sure to ground the coax to the coffee can.  This can 
will act as a waveguide beyond cutoff attenuator/filter for signals 
far below the GPS frequency.  The can would also narrow the field of 
view for the different satellites but pointing it slightly south from 
Southern California proved to be very reliable.  IF you do this, be 
sure to put small drain holes in the can and a "radome" cover over it.

I used to deal with these receivers in the Seiko pager-watch project 
about 10 years ago.

Burt, K6OQK

At 08:43 AM 11/11/2007, you wrote:

>I have about 6 of the 9390 series receivers. Most with Rubidiums and some
>with OCXOs. I had 3 of them running simultaneously with a Z3801A. They were
>on an HP antenna running through a 4 way splitter that is widely available
>on ebay. Two of the three locked properly and showed the proper time,
>however, they had the wrong, but same, day of year. I could live with that.
>The other one showed the correct day of year and time. About a month ago the
>one that showed the correct day of year totally quit lock, and I believe it
>also shows a low signal level, as the system check was OK. Too many other
>projects to play with it yet. Regards - Mike
>Mike B. Feher, N4FS
>89 Arnold Blvd.
>Howell, NJ, 07731

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at earthlink.net

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