Headless javAPRSSrvr

This article describes a trial of javAPRSSrvr on a Raspberry Pi (RPi) as a headless system (ie without integrated screen and keyboard).

HeadlessJavaprssrvrAbove is the RPi sitting on a TNC-X KISS TNC connected to the TNC’s USB port. In this case, javAPRSSrvr uses the supplied KISS interface, it does not use Linux kernel support for AX.25. Continue reading Headless javAPRSSrvr

Argent Data T3-135 review

I was handed an Alinco DR-135 + T3-135 to troubleshoot. The reported symptoms were that it “never repeated the owner’s Foxtrak based mobile station”.


The T3-135 is an OT3 tracker/TNC built on a card to fit inside the Alinco DR-135 in the place provided for their own EJ-41U TNC. The rear DE9 port provides data access to the T3-135’s A and B serial data channels.
Continue reading Argent Data T3-135 review

Open squelch data carrier detect for TNC-2

This article documents an open squelch data carrier detect (OSDCD) for TNC-2.

The TNC commonly derives Data Carrier Detect (DCD) from its modem chip (often a broadband energy detector is used in modem chips). DCD is used to enable decoding of incoming Receive Data (RD), and to block transmission whilst the channel is busy. Continue reading Open squelch data carrier detect for TNC-2

Foxtrak review

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:

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.

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

Earth continuity testing of amateur equipment

Electrical safety testing of equipment is covered by AS/NZS 3760:2010 In-service safety inspection and testing of electrical equipment.

This article describes how to test earthing continuity of amateur equipment. It is only one of several tests described in (AS/NZS 3760:2010), but it is most relevant to ham equipment, especially so-called ‘boat-anchor’ equipment. Continue reading Earth continuity testing of amateur equipment

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