Bicycle APRS and Hints

Setting up for transmit

I don't consider myself to be an expert, but I am providing some advice, in case some may find it helpful. Your mileage may vary, as might part numbers, equipment specifications, etc. For more complete information, start at Tucson Amateur Packet Radio's page.

My APRS setup consists of a Kenwood TH-D7 and a Garmin GPSIII+. I found the GPS plug/wire supplied with the Kenwood to be useless, since I doubt there is a wire stripper small enough to work with the very thin insulated conductors. I went to Radio Shack ("You have questions, we have telephones!") and bought a 3/32-inch stereo submini phone plug (Radio Shack 274-244), and a roll of 3-conductor wire (RS 278-871). I also bought a DB-9 male connector kit to hook up with the data cord that came with my GPS unit, since I opted not to modify that data cord. For info on various Garmin data connections, see their diagrams.

Please use 10 watts for soldering the conductors to this particular stereo plug. I used 20 watts. Using 20 watts will melt the stereo plug and render it useless. Luckily, I had purchased three of them, so my second attempt worked. The heat sink is a wonderful concept. Do take advantage of it.

My other advice is to make sure the GPS and the Kenwood are using the same data format, in this case, NMEA. As for setting a path, play around or do some research to see what works for you. The whole path thing is still a mystery to me. I find that "Relay,wide3-3" works well for my area, but found that "Relay,wide7-7" works better in Europe. Go figure. I wouldn't recommend "Relax,wide3-3". It may be amusing, and perhaps even more so after you've been driving for several hours and have stopped at a rest stop on I-84 to check why your position hasn't come back to you, but you can't do APRS with it.

Putting the APRS on the bike

The R.A.M. equipment mounts are wonderful. If they are tightened properly, they shouldn't work loose while riding. The mounting components are made with rubber, so the tension keeps things tightened, much the same way lock washers do. (You do use lock washers, right?)

I purchased the appropriate RAM mounts for the Kenwood TH-D7 (RAM-B-138-KE1) and the Garmin III+ GPSr (RAM-B-138-GA2). To snap the transceiver and the GPSr into their mounts is a challenge, but then, there is little concern of the equipment falling out during the ride.

I use velcro cable ties to secure the coiled up cable that goes from the radio to GPSr. So far, my questionable soldering technique* has held up, and the signal gets out as well as one can expect from a rubber ducky antenna that's 4 feet above ground.

* Or lack thereof. When I wrote that, I was enjoying my homemade radio-to-data cord. I had simply crimped the pins to the wires and it held up up for about 2 years, during automobile use, bicycle use, a trip to New England, and a trip to Belgium. The technique failed during a road trip in summer of 2003. Now, they are properly soldered, as they should have been in the first place.

Performance, to date

I used APRS during a recent public service event, but the results were inconclusive due to some software difficulties of a receiving APRS workstation. I wasn't reaching any digis very often, so an outside amateur who offered to help was unable to see my position and wasn't within simplex range of the event.

I later tried the same thing on the bike path, using a more substantial rubber ducky, and got better results, between Reston and the Rtes. 7 and 9 area west of Leesburg. Bicycle APRS is also an excellent way to attract rainstorms. That's why it's a good idea to carry some baggies for quick water-resistant storage. One of these days, I hope to get some good results between Reston and Purcellville.

As for power, the HT puts out 5 watts and I carry an extra battery pack for it. So, no gelcells at this point, though I purchased some Anderson Powerpole stuff, so I can connect a cigarette adapter socket with confidence with the electrical connection. So, maybe I can do a continuous out-and-back to Purcellville with APRS yet. I'll have to do some experimentation with some different ducky antennas to see how the signals get out. I have figured out how to stow my halfwave-on-2-meters dual band mobile antenna on my bike, using velcro straps.

Some APRS-related links

• A listing or two of symbols one can display while using APRS
• Current APRS activity near ARRL/W1AW
• Weather-related APRS activity
• Watch this space for my silly APRS tricks page.

The photos

Operating

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