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GPS Experimenters Kit

Stock of complete kits is exhausted. Some of the more critical parts may still be available. Contact the TAPR office after May 25 to see what might still be available.

GPS Timing Kit for Amateurs/Experimenters/Students/Scholars

Originally introduced in 2002, the Motorola M12+ GPS timing board remains one of the most accurate fixed position timing receivers available today. The M12+ Oncore can also be used for positioning and navigation applications. Synergy Systems, LLC incorporated the M12+ into a product called SynPaQ/E. Synergy Systems has made available to TAPR the following items which essentially make up a SynPaQ/E version XTS. These are currently available as a kit from TAPR. (kit items not sold separately) The condition of these parts would be considered used, but in good condition.

M12+ and the Motherboard

Motherboard and Interface Cable

The first item is the motherboard that contains the various power and interface circuitry and the attached M12+ as shown in the image to the right. The motherboard operates from 9 to 32 VDC and provides conversion from 3 V logic levels to RS-232 levels.

Also in the picture is the interface cable. The DE-9M connector shown is not standard RS-232 wiring. The non-standard DE-9M connector wiring was originally established by Motorola to minimize connectors and associated wiring for one of its automotive products by providing signal and power connections in the same connector. One could modify this cable or build an adapter cable as shown below to separate the power from the signal leads.

Antenna Cable

Antenna Cable
Included in the kit is a short cable with a right angle MMCX connector on one end to match the antenna connector on the M12+ and a bulkhead BNC connector on the other end to mount in the end plate of the housing.


Housing (black in kit)

The Motherboard slides into the housing's internal grooves. The front and rear panels are not included and must be fabricated by the user. A drawing for the front and rear panels is available here.

In Summary

You get:

  • M12+ Oncore GPS receiver already mounted on the mother board.
  • Mother Board which provides power and signal interface to the M12+
  • Interface Cable
  • Housing without end plates
  • Antenna Cable


User's Manual is here.
Schematic is here.

Avaiable Option

TAPR also has available a GPS Antenna - Motorola GCNAC1232A

DIY Adapter Cable Suggestion

Adapter Cable (not included)

Rather than modify the included short interface cable, one can build an adapter cable like that shown in the image to the right using a DE-9F connector at the right end of the drawing and a DE-9F on the left end. You end up with a Y cable where one branch with the DE-9F is the PC connection and the other is the power connection with a connector of your choice. The + power wire for 9 to 30 VDC would be connected to pin 8 of the DE-9F and the GND wire would be connected to pin 7 of the DE-9F and go to a separate connector or power source. If operation from a regulated +5VDC is desired, then the + power wire would connect to pin 6 of the DE-9F connector and the GND wire would still go to pin 7 of the DE-9F. DO NOT use both power pins. Use either a 9-30 VDC power source or a regulated +5 VDC power source, not both. With this adapter cable, a standard RS-232 cable can be used for connection to a PC. You are in effect building a null modem cable with power injection. Of course you need to watch that you plug the powered end into the SynPaQ mother board. Plugging the wrong end into the PC will likely destroy the RS232 interface of the PC.

Ordering Information

Sorry, GPS Experimenter Kit is no longer available

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