I have a 2-meter FM bicycle-mobile station.

I built my bicycle-mobile station in the winter of 2004 in order to be able to ride bicycle-mobile helping the Athens County Amateur Radio Association provide communications support to the April 4, 2004 running of the Athens (Ohio) Marathon (link). This event is the big public service event that the ACARA supports annually. For this event, the HT and antenna system were completely successful--I could successfully hit the repeater over the entire 26+ mile course except for one small space near the far-end of the course. (In 2004 weather conditions for this event were terrible: the temperature stayed around 36 degrees and there were strong, gusty winds and occasional heavy flurries of sleet.)

The bicycle is a late-nineties GT Arette steel-frame 21-speed hybrid. To this bicycle I have added full fenders, a rear rack and bag, a Sigma Sport BC-400 computer, a Terry saddle, a Princeton EOS headlight with 1w Luxeon LED, nine-LED flashing red taillight, two water bottle cages, handlebar extensions, pedals with straps, a tire pump, and handlebar-mounted push-to-talk (PTT) button. The front wheel and fork have been replaced; the originals were trashed in an accident.

The radio is an ancient ICOM IC-02AT. This big HT hangs on right side of the rear luggage bag. (If heavy rain threatens, I can put the HT inside the bag, and I have made a plastic "raincoat" to keep the bag dry.) For power I use the HT battery pack mounted on the transceiver or I stash a gel-cell or RC NiCd battery in the bag. I investigated mounting the HT on the handlebar but the size of this venerable transceiver makes this just about impossible. I have found that the current location of the radio on the rear bag works well enough; I can change power level and adjust the volume and squelch from the seat while under way. I shouldn't need to change frequency while riding.

I have added a handlebar-mounted PTT to the bicycle. I bought several of these velcro-mount PTT buttons at the 2008 Dayton Hamvention for one dollar each from a supplier of motorcycle communications systems.

I can also use an IC-2AT HT on the bicycle, mounting it as described above.

I have given some though to getting a smaller HT for use on the bike. If or when this actually happens, I'll look again at handlebar-mounting the rig.

The antenna is a 1/2-λ whip mounted on an aluminum sheet sandwiched between the rear rack and bag and secured with velcro. Initially, the antenna was an MFJ 1/2-λ extendable BNC-mount whip. While this antenna was inexpensive and highly effective, it was also relatively fragile. I have replaced the extendable whip with a Larsen SO239-mount 1/2-λ antenna which has proven to be just as effective but much more rugged.

For short rides, or when I don't want to mount the 1/2-λ antenna, I mount a whippy 1/4-λ directly on the HT.

Finding a suitable headset gave me a great deal of difficulty. I tried several headsets before finding one which works well on the bicycle and fits me when I'm wearing my helmet.

Initially, I tried an MFJ-293i earbud boom headset, which was was comfortable and didn't interfere with the operation of the bicycle, but the microphone audio was uselessly low.

Next, I bought a Radio Shack ICOM-compatible single-ear boom-mike with VOX when they were clearance-priced at $9.95, but I couldn't come up with a good way to mount this to my helmet and found that the gap between my ear and the speaker allowed a great of wind noise on receive.

More recently, after reading good reviews, I purchased a Pryme SPM-400A earbud mini-boom headset and a third-party remote PTT. Unfortunately, like the MFJ unit, this headset also provided transmit audio that was much too low; in addition, it suffered from a great deal of wind-noise while I was in motion even after I added a foam windscreen. On the other hand, this headset featured a socket for a remote PTT button, a feature that worked very well.

Finally, I found the solution already in my 'shack in the form of a single-ear boom headset I had built back in the '80s. Somewhat surprisingly, this headset, built around a Labtec computer headset and featuring a replacement microphone element of the correct impedence, fits well underneath my helmet. To use this headset with the handlebar-mount PTT button, I added a 3/32" socket to the PTT/interface-box. On-the-road tests have demonstrated that the headset is comfortable under the helmet and works well--receive audio is excellent, transmit audio is good, wind-noise is minimal even at speed, and the handlebar-mounted PTT works very well.

Prior to finding a suitable headset, I used an ICOM speaker-mic attached to a lanyard around my neck, the lanyard preventing any possibility of the speaker-mic falling and tangling in the spokes. Even after finding a suitable headset, I still use a speaker-mic and lanyard when I don't want to wear the headset. This solution isn't ideal for long rag-chews, but it works well enough for occasional, short transmissions.

For the 2005 Athens Marathon, I added Automatic Packet Reporting System (APRS) capability to the bicycle-mobile station in order to provide real-time graphical indication of the location of the race-leader to net control, the event organizers, and the viewing public. My investigations led me to purchase a used serial-version Delorme Earthmate GPS receiver (photo), a Byonics TinyTrak3 GPS Encoder (photo), and a Byonics GST-1 GPS Sentence Translator (photo). Because we planned to use the same frequency for APRS and voice, I built an interface box (photo) to connect all these items, the IC-02AT transceiver, and a speaker-mic together. I've since built a simpler interface for occasions when I don't need the speaker-mic (photo). W8KVK and KC8OVB worked on the APRS receive-side portion of this project. A major stumbling block in their portion of the project was the creation of a marathon-route map at the required resolution.

I used the same configuration for the 2006, 2007, and 2008 runnings of the Athens Marathon. During the 2007 running of the event, there was very heavy rain. The HT remained inside the rear luggage bag which was protected by a custom-made plastic "raincoat". I got soaked, and my speaker-mic failed due to moisture, but the transceiver and APRS gear stayed dry.

Links of interest:

• Byonics TinyTrak3
• Byonics GST-1 GPS Sentence Translator



• Short Takes: Byonics TinyTrak3 GPS Position Encoder (May, 2004 QST)
  by Stan Horzepa, WA1LOU, in QST Archives at ARRL

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