MOTOROLA FAMILY RADIO


Using Motorola Family Radio as Bike To Bike Communicator

By Jey Yelland <jey_yelland@agilent.com>

It's kind of amusing that we resorted to the Motorola Talkabout family band radios. Lynn and I are both hams. We got our ham radio licenses so we could rig the bikes for ham radios. The Talkabouts put out 0.5 watts. A ham radio could put out 5+ watts, greatly increasing the distance we could communicate. We just never quite got around to hooking up the ham radios.
<sigh>

We used the Motorola Talkabout Plus (has display of channel and "privacy" code numbers). We purchased the radios for about $110 each at a skateboard shop, about $10 below the going rate at most places. I also picked up a pair of Motorola speaker+microphones at about $30 each. The speaker+mics would become the foundation of parts for helmet wiring. I'm a handy guy with a soldering iron :-).

I first drew up the schematic for the speaker+mic. The speaker uses one pair of wires. The mic uses the other pair, the Push to Talk (PTT) switch is serially wired with the mic element. Next, I carefully unsoldered the cord from the head of the speaker+mic leaving the cord and formed plug to connect to the radio.. Next, I made up a wiring harness at the bare wire end of the cord that had a stereo mini-headphone jack (e.g. for Walkman headphones) for speakers and a sub-mini mono jack for the microphone. With judicious use of heat shrink tubing; a little PC board to mount the mic element; a mini-lever switch to serve as PTT; and velcro strips on the chin bar, PTT and mic; it all mounted in to the helmet neatly (but a little unwieldly). The speakers are the Bass Monster brand (~$20), they are designed for helmet installation for use with a Walkman or Discman. The mic element came from the speaker+mic parts. The PTT switch was a Radio Shack miniature lever switch. With the helmets all wired we set off for the MOA rally by way of OR ID BC AB MT ID OR and back home.

Day 1: The lever switch failed in Lynn's helmet. I replaced it with a spare I was carrying.
Day 3: The lever switch seems to be acting intermittently in my helmet; turns out to be a bend in the lever that needed to be bent back "just so" to work reliably. I had hooked the lever earlier in the day and not been particularly careful bending it back in to place.
Day 5: The tiny wires in the headphone jack of my helmet failed.
Day 10: The velcro loop side was coming unstuck from my helmet, probably hadn't been thoroughly clean when initially glued.

Lessons learned:

  1. We (almost) always did a radio check prior to rolling. No problems there; neither bike (K1100RS and R850R) offered much ignition noise. The family radio service is allocated 14 channels at around 460MHz. We had tried several other communicators that had lots of problems with ignition noise at 49MHz. Communications were easy at slow speeds (< 40MPH). At highway speeds communications were distorted. It actually became rather funny to compare notes at breaks at what we thought the other person said. I attributed this distortion to wind turbulence at the chin bar. The mic was velcroed to a position at about the position of the right eye tooth. Condenser mics are extremely sensitive. I think they were overwhelmed despite the small foam windsock. I will be trying a new location: under the foam padding a little farther back on the chin bar, at the cheek, to see if that helps.

  2. My wife and I typically ride within visual range. Thus well within the range for these little jewels. Occasionally we'd be around corners or separated due to traffic conditions. In most instances I was pleased that it worked farther than I thought it would. One time at south Lake Tahoe, past Emerald Bay approaching south shore, I had 500' of elevation overlooking a valley while Lynn was already down on the valley floor. Communications were *great*, perhaps 2 miles, maybe more! However, once I arrived on the valley floor too, with rolling hills, pine trees, and foliage attenuating the signal, we were lucky to talk 0.5 mile. However, this was better than having no communication at all. Lynn could tell me where she was and I could meet up with her much better than simply relying on visual cues.

  3. The 3 AA batteries in each radio would last on standby for up to 3 10-hour days. We probably transmitted only 10 minutes total on a set of batteries over the 3-day battery life. On the third day, the batteries might be too marginal to transmit successfully. However, with frequent break and meal stops, any problem with batteries could be easily corrected. The ability to have the radio completely detached from the bike was a design goal. The ability to rejuvenate the battery pack at any 7-Eleven or equivalent was extremely powerful. I don't think I'd change that. My wife liked to carry her radio in a jacket pocket. I opted for a long strip of velcro that fit through the top and bottom eyes of the radio and carried my radio on my tank bag.

  4. I'm still not satisfied with the reliability of the cabling from the radio to the helmet. The plugs and jacks are sizeable and the wire is tiny. Bulky gloved hands, bulky heavy jackets, wind and weather all conspire against these fragile components, compromising reliability. I've purchased components to switch over to standard 4-wire household telephone connecters, I have not completed rewiring the helmets yet. My concern with this approach is wet weather and my perceived fragility of these connecters. I will be adding strain relief in numerous places. I like the small flat wire. It will be much easier to run within the helmet. I will likely impress or melt pockets at the lower edge of the styrofoam on the shell side to tuck a minimum number of small connecters. At no point do I want to use specialty or difficult to replace components. I want to be able to replace anything at any Radio Shack.

I suppose that's quite a synopsis. Is this a premium J&M solution? No! Is it affordable and workable? Yes. I'm still experimenting and tuning the system. If you pursue a similar route I'll be interested to swap experiences. You'll definitely want to invest in a butane soldering iron (a Radio Shack item, I just *adore* mine!) for those quick little fixes. If you have questions I'll be happy to answer them if I can.

Regards, Jey
--
jey_yelland@agilent.com


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Last Update: Monday, December 21, 1998