W4MY-9 (APRS Tracker)

This is not to be construed as a comprehensive and well researched article on APRS. There is so much to this aspect of the ham radio hobby all one has to do is Google "APRS" and thee will be a litany of information to peruse.

This is about my mobile tracker I built, or should I say I integrated together. In a nutshell, this group of components serves to "report" my position on the Earth to anyone who cares to know. This is done digitally and automatically, requiring no action from me other than to turn it on. It is not a full blown APRS. I can't receive and interpret other position information as in a normal APRS setup. Its one way -- outbound. Sorta like raising my hand and shouting, "here I am!"

You basically need three things for an APRS tracker. First, GPS receiver capable of outputting its current coordinates to a standard RS-232 serial interface. The Garmen Etrex is my instrument (yellow thingy on the right) No fancy mapping here. Just bare bones position info and "breadcrumb" navigating. Think of it as a very sophisticated compass plus.

Second, you need a digital controller/position encoder to receive the position information from the GPS RX, compose the packet of digital data for dissemination, generate the FSK tones, key the PTT, and then send to the VHF transmitter. I selected the Tinytrak3 by Bytronics. It was a simple single circuit board kit about the size of two postage stamps. It is located under the metal shield to the left of the box.

Third, is the RF transmitter. In my case I used a junked VHF (2 meter) hand held where the battery holder clip had broken. It is an Alinco DJ-120. They quit making these in about 1990.

The box its in is not a necessity, but I packaged them together like this for convenience. When activated, the unit transmits on 144.390 MHz my position which is received by a local APRS gateway link to the Internet. My data is added to the Findu database, and anyone with access to the database can locate me via the Internet. Wow, and its "real time" also.

I'd like to clarify here that you DO NOT need a laptop or computer of any type to use and run the tracker. All digital info and manipulation is done in the firmware of the digital controller/position encoder. You do, however, need a computer to SET UP the tracker so it knows the call sign (of course) and SSID, and all the reporting parameters you desire. You download this to the TinyTrak3, remove your connection and plug in the GPS RX, and off you go. Remember, there's no receiving of position information, hence no need for computer mapping or a computer at all. Just blinkidy blink with a couple of LEDs to let you know its doing its thing!

Here's what you do. Go here to my favorite Findu interface, In the upper left type in my call and SSID, which is "W4MY-9" (no quotes) then click the "Find" button. You will see a Google map come up with my last location received. If you do it again only this time select the radio button "Track(Breadcrumb)" you will see my coming and going in the last 10 days.

I am going to have it up and running this next week through the weekend of June 9th. I'm participating in the Diabetes Association "Tour de Cure" in and around Oxford as a radio op, and they need to keep track of where we are, so this is how they do it.

Neat, huh? I know there is allot more I haven't covered, so post any questions about my setup here in the comments and I'll try my best to answer them.