Category: APRS

A few weeks ago I built up a Foxtrak kit, see Foxtrak build.

During testing, I noted that VK2ZEN-5 occasionally corrupts Foxtrak packets, or more generally MIC-E encoded packets. It is a known problem with aprsd which has not been fixed in more than 10 years.

As a result of the fact that one local digi (OT3) never decoded the Foxtrak (DK7IN firmware), I tried aprstracker0.11 and original TinyTrak(1) firmware.

The aprstracker evaluation is described at Review of APRSTRACKER v0.11 firmware, it was unsuitable.

The TinyTrak(1) firmware didn’t work with the OT3 digi either.

The matter of Foxtrak / OT3 interoperatibility is discussed in more detail at:

• Interoperability of FoxTrak tracker and Argent Data’s OT3 – Part 1; and
• Interoperability of FoxTrak tracker and Argent Data’s OT3 – Part 2.

A TinyTrak3+ was also evaluated, see TinyTrak3 v1.42 review.

Considering quality, price and performance, the Foxtrack works with most digis types but not OT3s, the DK7IN firmware has more feature than the original TinyTrak, but the combination is nowhere near as capable as the TinyTrack3+ which is less than double the price as landed in Australia.

I ordered a TinyTrack3+ (TT3+) from Byonics (US) website, and it arrived in Australia 8 days later by ordinary mail.

The configuration software worked reliably, but some default settings were not appropriate which led to unnecessary work. Continue reading TinyTrak3 v1.42 review

Further tests have been conducted and observations made of normal on-air traffic.

The question that arises is why everything else I have tried except
OT-USB and OT3 devices reliably decodes the Foxtrak (DK7IN, aprstracker 0.11, TT1), and the OT-USB and OT3 devices reliably
decode everthing else I have tried (including TT3+) except the Foxtrak (DK7IN, aprstracker 0.11, TT1). Continue reading Interoperability of FoxTrak tracker and Argent Data’s OT3 – Part 2

One of my simpler projects, just three electronic components and 140 lines of code… an open squelch DCD (OSDCD) for Paccomm Tiny2 Mk2 . Continue reading Open squelch DCD for Paccomm Tiny-2 Mk2

FoxDelta supplies a null modem adapter with their FoxTrak tracker. The null modem is used only during configuration.

The adapter is supplied with hex pillars (jack screws) on both DE9 connectors, which prevents the adapter being plugged directly onto the FoxTrak, or onto a PC USB-RS232 adapter with pillars. Continue reading Revision of FoxDelta null modem adapter

I have observed an apparent interoperability problem between FoxTrak tracker and Argent Data’s OT3.

Tests have revealed that two FoxTrak’s are not decoded by two OT3s. Continue reading Interoperability of FoxTrak tracker and Argent Data’s OT3 – Part 1

This article explains a method of setting the tx audio level of a Foxtrak using an SSB/FM receiver exploiting  Bessel zeros to calibrate the modulator. Whilst the Foxtrak is used in this example, the method can be used with any tracker or TNC that allows single modem test tones to be transmitted. Continue reading Adjusting Foxtrak tx audio using an SSB/FM receiver exploiting Bessel zeros to calibrate the modulator

Some AFSK sources such as TNCs, APRS trackers etc do not have facilities for sending single modem tones for the purpose of level adjustment which must be done using data packets which are a complex arrangement of high and low tones. Continue reading Adjusting AFSK FM tx level using a PC oscilloscope

Hams have used 1200Bd AFSK FM as the physical layer of AX.25 for decades, though with variable implementation quality.

Whilst the AX.25 packet networks of yore have all but died, the protocol is currently used with APRS, and so the related issues remain relevant… well as relevant as APRS remains. Continue reading AX.25 1200Bd AFSK FM – to pre-emphasise or not

I spent some hours today trying to receive a balloon travelling nearby on 2m 1200Bd AFSK.

At the end of the day, I note that the balloon was decoded by only two receivers located in or near Sydney and that resulted in a record to APRS-IS. One was my own station which decoded three packets, and VK2RHR-1 which relayed 16 packets.

Given the balloon’s flight, it is notable that it was not relayed by VK2AWM-1 (which was 40km closer), VK2RAG-1 and VK2RTZ-1 at Gosford and Newcastle, and at least four igates in Wollongong, Sydney and Newcastle. Continue reading Diagnosis of APRS reception problem