[time-nuts] 9390 GPS RX

Mark C. Stephens marks at non-stop.com.au
Tue May 21 06:42:21 EDT 2013

Hello Fellow time nuts,

I received a Datum 9390 GPS receiver I bought off eBay today. It had a PSU fault and I am running it off a bench supply until I can get the PSU working again. All the PSU does is supplies 28V so I can probably adopt a more recent supply to fit if I can't fix the old one. I pulled the PSU apart and so far found a blown triac. There is bound to be more 'things' blown but I want to see if it's worth repairing first. I mean, it's not much use repairing something that proves to be useless?

Funnily enough in the back of the Manual binder was a second manual. A service Manual for a Trimble 5000A GPS/TIME frequency monitor. I'll scan it if anyone needs it?

This particular 9390 is an odd Chap, doesn't look at all like picture in the supplied manual. http://www.vk2hmc.net/blog/wp-content/uploads/2013/05/9390-fr.jpg

When I opened it up, http://www.vk2hmc.net/blog/wp-content/uploads/2013/05/9390-insides.jpg  I saw an Efratom FRK! http://www.vk2hmc.net/blog/wp-content/uploads/2013/05/frk.jpg

I am having a bit of problem identifying the GPS module. It says Trimble navigation on the board: http://www.vk2hmc.net/blog/wp-content/uploads/2013/05/gps-bd.jpg
I measured the antenna Jack for the expected 15V normally on a Datum 9390, but found it was 5.1 volts.
I could not get rid of the Antenna feed error until I put a 50 ohm terminator on it. I tried higher values (75-180R) but the only value that cleared the feed error was 50 ohms. So I used a BNC 'tee' and terminated the output of the GPS distribution amp to the 9390. I fear this GPS RX requires an antenna with a down-convertor -or- a whacking great L1 signal. I always thought the 9390 had a Trimble svee6 module in them. But this one's positively ancient.
I have entered my approximate co-ordinates to see if it finds any birds but so far no luck.

If you know anything about this GPS board, please leave me a message?

The interface convertor from the Trimble to the Datum: http://www.vk2hmc.net/blog/wp-content/uploads/2013/05/gps-bd-if.jpg is labelled "Datum TANS interface".


Complete blog post is here: http://www.vk2hmc.net/blog/?p=178

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