APRS equipment for the G6KIZ-7 mobile callsign


G6KIZ-7 – (Mobile 1) – Equipment
For mobile operation I had a choice of 2 rigs and used SSID -7 and -9. I now use a TMD-700 exclusively for mobile as this gives at least some chance of responding to calls while mobile.

Antenna : Short dual bander on a mount fitted to the top of the tailgate. I had to take a hacksaw to the mount to remove a protruding tab which would have caught on the car roof. I use the same antenna for the G6KIZ-9 setup.

Transceiver : THD-7E I bought a couple of 9.6v high capacity battery packs for this rig – I have anything up to a couple of hours a day on my daily commute and a battery will last for just over 4 days. With the 9.6v battery the high power setting is 5 watts but I run on 0.5 watts into an ancient Microwave Modules MML 144-30 linear which produces around 20 watts.

GPS Receiver : A serial GPS “mouse” – I’ve butchered the cables to fit a USB connector for power which fits an existing mobile phone adaptor and the 2.5mm stereo jack required by the THD7-E.

My station costs
Antenna : Around £40 including the mount.

Transceiver : £140 from eBay. Replacement high capacity battery packs £25 from a US seller on eBay – a great deal as I was able to sell the original battery pack for about £10.

Linear : Around £30 on eBay.

GPS : Around £20 on eBay.

Problems encountered
I was having problems with rogue beacons giving wildly inaccurate positions.

By observing the position display on the TMD-700E it was obvious that the rig itself was transmitting wildly inaccurate data which eliminated my initial suspicion that the data packets were being corrupted.
As both the THD-7 and TMD-700 use a rather delicate 2.5mm GPS connector I initially thought that this was the cause and replaced the cabling but the problem persisted. I am now pretty well sure this was caused by a faulty GPS unit as replacing it with another cheap unit from eBay seems to have cleared up the problem.

When mobile this is strictly a reporting only setup as trying to create messages or even read them would likely end up in an accident. Unfortunately replies to old messages tend to fail as either one of both stations are out of range of each other and a digi.

Kenwood THD-7E handy with built in TNC


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