Perhaps not! I'll look into it further.

73!

Don't forget, APRS is not about sending your GPS position. That is simply a part of the whole thing (although it seems to be the most popular). It's all about local tactical data distribution. The kind of data that is distributed is, of course, lat/lon coordinates of objects, text messages, and telemetry. The data can be generated automatically by microprocessor devices, or by an operator. When the data is sent, all receiving stations will see it and operators can act on it. Originally 'all receiving stations' meant 'those radios tuned to the local frequency', but now it could mean any station hooked up to the internet if desired.

I meant to add a summary of the absolute cheapest way you could try APRS.

Assuming you have a PC and a radio you just need a cable to hook them up. If you only want to receive and decode packets you need to connect the radio speaker output to the PC sound card mic. input. If you want to transmit, you hook up the PC sound card speaker output to the radio mic. input, and connect a transistor driver from a PC parallel or serial port line to the radio PTT. Here's a simple example [1], but there are many designs on the net. Such a cable would be extremely cheap to make, and software of course is free.

Naturally, you will need a station at the other end, although it's very Zen to ask "what is the sound of one APRS station transmitting?".

73!

[1] http://www.qsl.net/wm2u/interface.html

This TNC is pretty compact and comes with an inbuilt GPS. Looks like it could be ideal as a compact APRS tracker.

http://www.crosscountrywireless.net/aprs_tnc.htm

costs about $150.

That TNC is actually derived from Bob Ball's design (link [1] in my original message). It has been modified slightly to make it into a product, rather than a hobby kit. It's ideal if you don't want to grab a soldering iron and put your own together, but if it is $150 then it's twice the price of DIY.

The DIY project doesn't include the GPS SIRF engine and the USB interface components etc, then you will also need a Microchip PIC programmer to flash the PIC16F88 microcontroller so even at $150 is quite a good place to start esp if no you don't have a external Handheld Garmin eTrex to hand or a even an old Trimble Lassen LP GPS development system to hand.

The AX.25 radio packet protocol also seems ideal to use the ancient Videotex technology such using the ancient Prestel or Minitel terminals in the days before the Interweb. But this would require full duplex communications with a 75bits/sec Tx to go with the 1200bits/sec Rx.

http://www.youtube.com/watch?v=wq53DO7zL_g


This video is quite interesting - a BBC micro computer teletext adapter from the early 1980s. Basically just a TNC + UHF reciever/line decoder being used for free wireless software distribution broadcast over a region the size of the UK.

http://www.youtube.com/watch?v=ctxZWEVJ1S0

APRS certainly looks like something quite interesting for the HAM amateur. Its a little weird though to think that it is a possibility that emergency data communications could one day rely on the amateur HAM geek with an interest in 30 year old fall back digital communications technology, his/her soldering skills and a charged 12V car battery.

It's common where I live for first responders to ask amateurs to help with communications for large incidents. It's not so much a possibility as it is something the local RACES group trains for regularly and gets to do for real every so often.