MOTOROLA FAMILY RADIO
Using Motorola Family Radio as Bike To Bike Communicator
Jey Yelland <firstname.lastname@example.org>
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.
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.
- 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.
- 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.
- 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.
- 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.
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Last Update: Monday, December 21, 1998