What is this interesting

Symmetricom Unit?


The board illustrated in the photos below was sent me by a friend in China, who knows nothing about where it came from. It appears to be complete and might be in working order, but I'm having a hard time identifying it, and have not found the correct way to power it up. If you can help me, please send an email to:

General Description

The unit is labelled as an "FBCB", which may be a "Force Battle Command" sub-system, some type of military navigation and positioning system, although reliable internet information is scanty. It carries a label with 'Sec Code: EP92-01235A', and the board is labelled 'Symmetricom Inc 090-03851-02 REV A'. The PCB carries the number 'LAC-10 2905'. I take the date of manufacture to be approximately 2005, although there are component date codes back to 1998. The board is about 140 x 100mm in size, and probably a 4-layer board.

Without question, this unit is a GPS Disciplined Reference of some type. It quite prominently sports a nice Symmetricom 5MHz OCXO, labelled 106824-001. This OCXO is electrically trimmed via SPI interface, and I have found some superficial data for it. The performance given in the data looks very good.

The GPS receiver module on board is a Furuno GT-8031C. There's no obvious power connector, just a 2x40 SMD header P1 for some type of ribbon cable, and a dual shielded RJ45-type connector, P2, labelled '2-WAY DOWNLINK' and '2-WAY UPLINK'. The second of these may also be the source of power, as I've traced the 12V and ground to it. Both of these connectors are on the bottom. There's also a 5-pin 'Debug' header J1 on the top side, in the top left corner.

There are two SMA connectors on top (GPS ANT and 10M), as well as two smaller ones (78M and 58M). On the bottom there are two corresponding TCXOs (78.643MHz and 58.982MHz).

Bottom View - click here for high resolution version

Top View - click here for high resolution version

Can you help me identify this unit? I would particularly like to know:

  • What it does
  • What the connnector pinouts are
  • How I can power it up
  • How I can talk to it
If you can find me a schematic or manual for the unit, even better! I only have one of these boards, and don't know where there are any more.

Murray ZL1BPU

Copyright Murray Greenman 2011. All rights reserved. Contact the author before using any of this material.