Interoperability of FoxTrak tracker and Argent Data’s OT3 – Part 2

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

Revision of FoxDelta null modem adapter

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

Adjusting Foxtrak tx audio using an SSB/FM receiver exploiting Bessel zeros to calibrate the modulator

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

AX.25 1200Bd AFSK FM – to pre-emphasise or not

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

Diagnosis of APRS reception problem

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