APRS Projects

APRS Position Encoder

The idea of making a stand-alone APRS encoder is certainly not new - several example uses (some quite zany) are given on Bob Bruninga's website. All the parts for this project are available by mail-order, either from the usual suppliers (Maplin etc) or from Tuscon Amateur Packet Radio (TAPR) in the US...

  • TAPR PIC-E - Single Board GPS Encoder Kit.
  • TAPR GPS-20/25 Interface - Power Supply for GPS.
  • Garmin GPS-25 OEM Module
  • Hand Held Transceiver
  • A 12V Gel Battery - and possibly charging circuit


The TAPR PIC encoder board is intended to be used as an implementation of the APRS MIC encoder. The board above contains only two ICs (not counting the 78L05 voltage regulator !) - the Microchip PIC 16F84 microcontroller and an MX-614 modem IC.

The onboard PIC microcontroller can be programmed in situ using an on-board programmer. Working example programs and further information is available from TAPR's website.

The following free development tools are available :

TAPR GPS-20 & GPS-25 Interface Board

The McKinney Technology Garmin GPS-20 & GPS-25 Interface Board is available through TAPR. Provides mounting and a regulated 5V supply - also support for a lithium backup battery and interfacing for certain Garmin GPS boards (which output TTL levels) to RS232.

Garmin GPS-25

The Garmin GPS-25 is a bare board, and as such has no display or user interface, only providing the required NMEA 0183 output to an RS232 port - It is intended to be built into a larger system (such as this project) by a systems integrator. The board, interface cables and antenna are available from Maplin Electronics (order no VX20W).

Once completed, the whole setup could be mounted in a waterproof enclosure, and may be carried in a backpack - this project is probably ideal for outdoor club events or even scouting (the legality of this is yet to be decided), allowing a base to keep track of remote persons or vehicles.

Updated - 09/08/2000

A.D.Russell (G0VRM)/P.R.Sheppard (G4EJP)