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The Amateur Amateur: APRS, the Beginning

06/10/2010

By Gary Hoffman, KB0H
ARRL Contributing Editor

I became interested in APRS (Automatic Packet Reporting System) after watching a presentation on it a few years ago. The presenter described some of the interesting things that could be done with APRS, which, I think, sold many of us right then and there. Maps showing the locations of cars, boats, people, parade floats, bicycles and especially balloons were a real eye-opener. Regrettably, though, the presenter drifted off into a rather dry description of a complicated APRS program and soon lost the attention of most of the audience.

Evolution 

I was still interested enough in APRS that I Googled it the next day. There were a great many sites dedicated to the field, so I skimmed a random sampling of them. Wow! Everything I read seemed highly technical, and none of it described what APRS actually was. The only solid piece of information I was able to garner was that if you called it Automatic Position Reporting System, the APRS Police would come knocking at your door.  But just what was APRS? I still didn’t know.

Skip forward a few years.

The term APRS caught my notice from time to time, so I periodically went back to the Internet to see if I could figure it out. I didn’t have much luck. I did find a commercial Web site, byonics.com that sold APRS equipment, but all of the products seemed to be geared toward hams who already had a pretty good grasp of the subject.

I recently spent a lot of time working with digital formats, specifically packet, and messing around with TNCs (Terminal Node Controllers, see my column “The Amateur Amateur: Not Exactly Plug-And-Play”). APRS came up repeatedly in the TNC manuals, and I even found that one of my devices was designed only for APRS use. So, naturally, I found myself once again getting interested in the topic.

Mapple 

I revisited the Byonics Web site. As before, most of the products looked tantalizing, but confusing to a beginner like me. But there was one new product that managed to grab my attention. It was called a MicroTrak-Ready-To-Go (MT-RTG). Basically, it was a simple vehicle tracker. It didn’t have to interface with anything and it could be powered from a cigarette lighter jack.

I especially liked the “ready to go” part. I read the product description very carefully and concluded that, yes, even a complete idiot could operate this device. Finally! An APRS product made with me in mind! I ordered one on the spot.

My MicroTrak soon arrived. I read the instructions again, just to make sure that it really, truly didn’t require a complicated transceiver, a rotating dish antenna, a supercomputer or any competency on behalf of the operator. Nope. This device really was plug-and-play. So I plugged it in. And wonder-of-wonders, it played.

And Now an Announcement from…

During the years that I had nibbled around the edges of APRS I’d come across a Web site called Findu.com. It was pretty nifty. All you needed to do was type in the call sign of an Amateur Radio operator and his/her location would pop up on a map.

Well, no, it wasn’t quite that easy, but it was close. It showed the location of any ham sending out APRS packets. But as it turned out, several hams that I knew did show up on the map. So, as soon as I finished installing the MicroTrak in my SUV, I ran to my computer to “see if I was there”.

Yes! I was! And I soon found that there were a number of other Web sites, such as aprs.fi and www.openaprs.net that showed a plethora of other APRS information in addition to just a location. It all looked interesting, but I didn’t know what any of it meant.

Cue dramatic music. That was when it happened. I was standing at the very edge. And the moment that I started to look up those strange codes and symbols, I toppled over the edge and was well on my way to becoming an APRS junkie.

So, what does a junkie do? He gets other people hooked. One day I told Steve, KC0QMU about my MicroTrak. I even dragged him over to my SUV and pointed out the unit (it’s just a tiny plastic box) and its unobtrusive antennas.

He didn’t look impressed.

I Never Thought a Company Could Be My Soulmate

That same day my wife Nancy and I drove to Montgomery City to attend the graduation of our niece Ellie. That’s about an 80 mile drive each way. It was pretty late at night by the time the ceremonies had ended and we’d started back home. I had the FM radio, my 2 meter transceiver, and a police scanner all going in an effort to keep us awake. Nancy and I bellowed at each other over the racket, talking about the graduation, Ellie’s future and strangely enough, APRS.

I guess we had perhaps another 30 or 40 miles to go when -- and I still can’t believe I actually heard it -- my call sign came over the ham radio. I picked up the microphone and answered.

It was Steve. He was tracking us using aprs.fi. He knew where we were and which other vehicles near us also had APRS trackers (this was getting a little spooky). It seemed that after our meeting that morning he’d started looking into APRS, had gotten interested and had even gone so far as to order a MicroTrak himself. For a very brief moment I thought I’d been granted stunning powers of persuasion. But, of course, that was just the fatigue of a long day and a longer drive. APRS had sold itself.

At some point during the conversation Mike, WD0GSY joined in and told us how we could greatly expand our APRS capabilities by using transceivers rather than our simple transmit-only trackers. Now before I became hooked, I would have shaken my head at the complexity of it all and given Mike noncommittal grunts in response. But that night it all seemed magically possible.

“Think Differently”

A few days later, after I had studied the strange symbols and such that my MicroTrak was transmitting, I decided I would take advantage of Byonics’s free software download and reprogram some of my unit’s settings. For example, when I bought the device I asked Byonics to program it with the call sign KB0H-10. I had since learned that KB0H-9 was more appropriate for a vehicle (at least according to one Web site). I also wanted to change the message “MT-RTG” to “St Louis County ARES” (hey, I’m proud to be a member). So I got my laptop all prepared and hauled it to my garage. I connected it to my MicroTrak and...nothing. Well, not exactly nothing, I got various error messages.

Ah, that was more like it. Everything had gone far too smoothly up to that point. It was like I hadn’t earned my stripes yet. So, after re-reading the instructions several dozen times (I always find something I’ve missed before, just like watching Star Trek reruns), and after getting the correct gender-changer/null-modem, and after setting the COM port to 4800 baud, and after screaming and cursing for a very long time, I was able to successfully reprogram the MicroTrak.

And it still worked!

I told Steve about my reprogramming effort and he asked if I could put the message “St Louis County ARES” into his new unit as well. He is, after all, our ARES Emergency Coordinator.

Oh sure, I said, confidently.

Take a Page from the Book of Bart 

So one morning we got together in a QuikTrip parking lot and wasted a great deal of time squatting behind Steve’s SUV, watching the same error message pop up over and over again on my laptop’s screen. I was tremendously embarrassed. I even tried connecting to my own MicroTrak, but the same error message appeared. The only thing we accomplished was to give travel directions to various lost people who had apparently been attracted by our antenna-festooned vehicles. I guess we must have looked “official.”

Naturally, when I got home and took the MicroTrak and laptop down to my shack to experiment further, the very same devices that had given me fits all morning suddenly worked absolutely perfectly. I think they sensed the proximity of numerous lethal power tools.

But such irritations were not going to deter me from my next goal.

Next time: My APRS base station.

Editor’s note: ARRL member Gary Hoffman, KB0H, lives in Florissant, Missouri. He’s been a ham since 1995. Hoffman says his column’s name -- “The Amateur Amateur” -- suggests the explorations of a rank amateur, not those of an experienced or knowledgeable ham. His wife, Nancy, is N0NJ. Hoffman has a ham-related Web page. Readers are invited to contact the author via e-mail.



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