[time-nuts] Datum 9390 Problems

Magnus Danielson magnus at rubidium.dyndns.org
Mon Mar 23 19:31:15 UTC 2009


Thomas Folkers skrev:
>    On Mar 22, 00:00 UT, both of our Datum 9390 model GPS receivers/time
> code generators started producing erroneous day of year and actual year
> values.
>    Instead of day 81, it said 96 on the front panel, but produced day 196
> in the IRIG-B time code.
>    They also reported the year as 2007.
>    The two units are locate 200 miles apart on a remote mountain location
> and are used to control radio telescopes.
>    The unit on Kitt Peak. Arizona was purchased in 1998 and has a model
> number of:
>    9390-6000; Firmware version, I think, of N500/S118/DT101C
>    The Unit on Mt. Graham, Arizona was purchesd around 1995 and is model:
>    9390-52333; Firmware version: N502/S118/DT300KP.
>    Neither unit has ever undergone a firmware update. I'm pretty sure
> this may be the root of the problem.
>    Can anyone help me here as Symmetricom doesn't seem interested in 
> answering my tech support calls.

I got a call from a friend that had a call from one of his customers 
that had all their receiver fail in the same fashion. Their Symmetricom 
receivers however reverted back to an older date. I will try to get the 

My conclusion is that it is a bad 1024-week wrapping routine in action. 
The lack of firmware upgrade is most certainly the root cause as the 
typical way to resolve it is to use a reference date near time of first 
shipping as reference and then calculate away from that.

Unless you get firmware upgrades your receivers have just become a piece 
of junk and you are expected to buy new...

So, you are not alone with this problem.

The lack of firmware upgrades that handles dates and signal upgrades 
(such as PRN 31 and PRN 32) is a constant source of GPS failures. It 
also has a very scary tendency to be coordinated. GPS receivers older 
than 10 years should maybe not be kept in production unless it is known 
to work and be sufficiently supported.

So, I got one of those "I told you so" moments today.


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