APRS equipment for the G6KIZ-9 mobile callsign


Kenwood TMD700e mobile APRS transceiver

G6KIZ-9 – (Mobile 2) – Equipment
For mobile operation I have a choice of 2 rigs and use SSID -7 and -9

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-7 setup.

Transceiver : TMD-700E This rig has a number of benefits over the THD-7 the main ones from my point of view being the large, easy to read, display and a 50 watt output.

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 TMD-700E.

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

Transceiver : Around £280 from eBay.

GPS : Around £20 on eBay.

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

By observing the pos display on the TMD-700E it was obvious that the rig itself was transmitting wildly inaccurate data which eliminated my initial suspition 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 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 TMD-700E hack
I discovered this one by accident.
If you would like your TMD-700E to turn on automatically when power is applied try this….
Press and hold PTT so rig is transmitting.
Turn off power to the rig (typically by turning off the ignition).
Continue to hold PTT and turn power back on after which you can release the PTT.

After this process my TMD-700E turns itself on with the ignition. Using the rig power button to turn it off breaks the spell. Sometimes it doesn’t come on for reasons unknown but repeating the above steps restores the behaviour.


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