Foxtrak build

Foxtrack is an inexpensive kit form basic APRS tracker, taking a GPS NMEA feed and producing audio frequency shift keyed output to key an FM transmitter. It incorporates a limited TNC function and some intelligent position reporting algorithms


Above is the top view of the Foxtrack PCB.


Above, the underneath of the Foxtrak PCB.

The Foxtrak is also supplied with a null modem for configuration.


Above, the top view of the null modem PCB.


Above, the underside of the null modem PCB.

Construction issues

A number of problems were encountered in constructing the kit:

  • five plated through holes were fully blocked with solder;
  • one pad lifted during attempts to clear a blocked hole;
  • some other plated through holes were very tight fit for the supplied components, partially obstructed by solder;
  • all diodes and one LED were missing;
  • the switch did not suit the hole drilled in the case, and the case had to be slotted to provide clearance for the switch;
  • the holes in the case for the LEDs were too small to accommodate the LEDs;
  • The pillars on the null modem prevent it being plugged directly onto the Foxtrack, they need to be replaced with some 4-40 screws with low profile heads

If the Foxtrack did not have these problems, it would be stunningly good value… it is very low cost. If it cost double and had none of these problems, it would still be very good value, but might not be as good in value as its competitors.

The deviation was set at 2.2kHz modulating frequency to 3kHz, and checked at 1.2kHz to be 1.6kHz deviation confirming correct pre-emphasis.

Screenshot - 18_07_2014 , 16_13_59

Above is an off air recording and the preamble is 66ms (configured for 100ms, reduced by some delay in tx operation and rx mute opening). Though the high tone appears a bit lower than the low tone, the IC2200H reciever used exhibits about 1dB too much de-emphasis.

On air drive testing went reasonably well with the original (DK1IN) firmware with some recieving stations and not others… more work to be done.

Tests were also conducted with APRSTRACKER, but it did not work properly, see Review of APRSTRACKER v0.11firmware.