APRS Geekery

Here’s one for the techie, electronics, and/or ham radio nerds.  APRS is now fully operational on my bike.  Here’s how I did it.

Previously, I had the bike set up so I could chat on a local 2 meter repeater while I was riding.  I used a Radio Shack HTX-202, powered off the bike through a voltage regulator, connected to my 1/2 wave antenna, a headset in my helmet, and a push-to-talk (or, as my girlfriend calls it, release-to-listen) switch on my left handlebar grip.  It worked rather well, with a few limitations – power, as I was limited to 5 watts, and my inability to make adjustments while underway.  You’d think that I wouldn’t want the distraction of doing such a thing, but I often found myself wanting to tweak the volume or squelch, and on the longer rides I take I go in and out of various repeater coverage areas fairly regularly, so I want to switch to a different frequency.  Mostly, I found myself wanting to kick back and enjoy the ride rather than fiddle with the radio, so after all that work, I ended up not putting it to use.

Rather than let the equipment go to waste, I realized that I already had most of an APRS station put together.  All I needed was a tracker and a GPS (my TomTom unfortunately doesn’t provide a data output).  After some research, I picked up a Byonics TinyTrak3+ with a matching GPS receiver.  Because I’m not that great with electronics, I bought a preassembled version.  You can buy it in kit form for less, and if you’re even slightly clueful with installing components on a circuit board you should have no problem building it.  Unfortunately, my alleged ready-to-go solution had some issues.  Byon was very responsive and great to work with through the troubleshooting. I even sent my TinyTrak3+ back to him to inspect at one point. The issue turned out to be an incorrectly pre-wired cable, which he replaced promptly.  With that, I had my plug-and-play APRS station on the air.

So here’s the complete setup, in operation.  The GPS receiver magnetically sticks to the top of my gas tank and plugs into the TinyTrak3+.  Power comes from the same three-outlet adapter that I’d already wired into the bike’s switched power wiring to run the radio and my TomTom.  The TinyTrak3+ plugs into my HTX-202, now set and locked on 144.390 MHz, the national APRS frequency.

If you know the HTX-202, you’ll notice that I don’t have a battery attached to it.  I’ve read that running this particular radio off external power for long periods of time with a battery attached can overcharge and fry a battery, so in this application I always run without one. It also makes the radio a little bit smaller, too.  I’ve put a piece of electrical tape over the positive battery contact to prevent any chance of a short.

The entire station (except the GPS receiver, of course) fits in the lockable compartment on my fairing.  I’m quite glad I’d bought a replacement lid with a working lock from the same guy I bought my saddlebags from when he offered!  This compartment is also a bit larger than the one on the left side of the fairing, and everything, including the extra lengths of wiring, fits inside just fine. I leave the equipment plugged in and turned on, powered on and off by the ignition.  This way, whenever my ignition is on, the APRS station turns on as well, and begins beaconing my position automatically.

All you need to track me is this link: http://aprs.fi/#!mt=roadmap&z=11&call=a%2FKJ1H-9  You don’t need a ham license to do this, because all you’re doing is viewing data that’s been exported to the internet.  I’m the one actually transmitting the data on the air, and I do have a ham license, so we’re covered. It’s a pretty cool site.  You can change how far back you want to view data, and it will plot my general route on the map based on where and when I was heard.  If you’re feeling geeky, you can hover over each dot where I was heard and see through what stations each transmission was rebroadcast (digipeated, to use the technical term).

I plan on taking a quick ride this afternoon before taking off for the weekend (a non-bike related trip this time).  I’m looking forward to seeing how well I’ll be able to see my route when I get home.

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