APRS test drive – 20141114

A short test drive was conducted to evaluation APRS effectiveness in capturing a motor vehicle journey of about 10km.


Screenshot - 14_11_2014 , 10_13_24

This journey is a regular one (the run to the local shops) and due to its familiarity is a good benchmark for performance.

The configuration:

  • Foxtrak with TT3+ firmware set for high rate smart beaconing;
  • VK2OMD-3 iGate and viscous digi using IC2200H and Paccomm Tiny-2 MK-II with OSDCD, aprx v2.09 on RPi;
  • two local digis, VK2RGI-1 has had its deviation reduced to a sensible level though still lacks pre-emphasis (Argent Data T3-135).

The results were good, about as good as achieved on this route and considering that the channel was quite busy, probably a little above average.

The Tiny-2 MK-II reliably decoded the TT3+ even when in some scratchy spots in town.

This was a low tech configuration, the TT3+ does not use open squelch DCD but previous experiments have shown that the Argent Data implementation in OT-USB didn’t work as well as using broadband energy detect and squelched radio.

The TT3+ waveform was decoded fairly reliably by VK2RHR-1 which uses a Argent Data T3 (does not decode original Foxtrak and some other trackers).

No evidence that the TT3+ commenced to transmit on a busy channel (this was a problem with OT-USB OSDCD and a significant cause of lost packets).

There were the usual record corruptions, on this occassion due to sumissions by VK2KAW and VK2YGV-5, 15% of the records accepted by APRS-IS were corrupted. APRS-IS doesn’t do much checking, and in this case accepted delayed records and assigned a new timestamp to the observation even though the records contained an internal accurate timestamp.

Overall, it worked well, as well as any configuration tested and better than most.


Though it might seem pretty basic, a 30 year old TNC at the iGate, old architecture tracker albeit with newer waveform generation, it worked, and worked as well if not better than some configurations using newer equipment.