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Autocom and Radio Installation

A long and winding road … Autocom + Radios

From: David Brick <>
Date: Sun, 31 Jan 1999 18:07:22 -0800 (PST)

Summary: This was a *very* long and winding road, with an expensive toll and many nonproductive detours. The story does, finally, have a happy ending. The first segment below describes the selection and installation of the intercom system and the radios. The second segment explains modifications to improve the system.


1. The Situation.

    My wife and I both ride our own bikes, and it’s sometimes hard to communicate: is it time for a break? do we turn left here or go further? what a wonderful sunset! It was important to Mary that we be able to communicate better than we could by waving our arms and pointing. It is important to me that she be happy, and I enjoy technical challenges. I thought it’d be elegant if we could communicate, whether we were on one bike or two, and that the setup be invisible, always ready for use, and require as little rider fiddling as possible.

2. Intercoms.

    Intercoms are fun, and we have enjoyed them when riding two-up. None we’d tried worked at over 50-60 mph. (We’ve not tried the Colletts, but were put off by the radio case hanging off the helmet and the battery case hanging off the rider.) We finally bought an Autocom Pro3000: VOX (hands-free operation), AGC (volume goes up automatically with the increased noise from higher speeds), and it’s possible to connect them to radios for bike-to-bike communication. The U.S. distributor is TopGear Accessories in New York.

3. Autocom Installation.

    • a) Headset installation.

      • The headset consists of microphone and speakers. The speakers are fairly thin and backed with velcro, so they can be placed in the ear recesses of the helmet, where they’ll stick to the liner, but still be movable for location adjustment. I played with them for awhile, but they took a bit too much room and I felt pressure on my ears and earplugs. I finally removed the front padding from the helmet (ear-to-ear around the front was one piece), peeled back the lining fabric, gently scraped out about 1/4″ more clearance from the helmet’s EPS liner in the ear area, put the speakers in place, then refastened the lining fabric over the speakers. The speakers and the rest of the headset connection are now hidden under the lining fabric; the helmet goes on a lot easier, and is much more comfortable. The microphone lives on a flexible metal stalk. The stalk emerges from under the cheek padding at the bottom of the helmet, and snakes up so the microphone sits in front of the wearer’s mouth.

The headset has a DIN plug, which hangs a few inches down from the right side of the helmet. (The first time I mounted the headset, the DIN plug hung down on the left; it was difficult to manipulate the helmet D-rings with the plug on the left side.) When the Autocom isn’t being used, a Chap Stick cap with a bit of felt inside (for tightness) fits snugly over and protects the DIN plug.

The installation was frustrating because one of the headsets was defective. I called TopGear, and they sent a replacement headset. The system still didn’t work, and I couldn’t figure out why. I ended up shipping both intercoms and all three headsets back for their evaluation. It turned out that the replacement headset was also defective; a second replacement was needed. While TopGear was consistently helpful and friendly, I was miffed that they charged me for all the shipping costs (in both directions) for these defective-out-of-the-box components.

b) Autocom installation.

      • Slightly larger than a pack of cigarettes, it velcroes in place on top of the air filter cover on my R11RSL, under the front edge of the seat. The rider’s seat still mounts in any of its three positions with no interference. The connecting cable to the rider’s helmet can be pulled out between the seat and the tank, and is long enough to reach my helmet while I’m standing next to the bike. When Mary rides pillion, we use an ordinary 5-pin DIN computer keyboard cable to extend the pillion’s cable; the extension emerges from under the left side of the passenger seat, by the front saddlebag mount, through a convenient joint in the bodywork. The DIN cable is stored in a vacant compartment in the fuse box. Those who don’t mind holes in their bikes or more visible modifications could wire up a surface-mount DIN socket and power switch, so that the seat wouldn’t have to be removed to connect things. The cables could be kept in a pocket of the rider’s jacket. But I ride alone a lot, and enjoy the bike’s unmodified look.

The installation works very well. The AGC allows us to talk fairly easily at any speed we might ride when two-up. Mary had a lot of trouble getting used to talking loudly and “forward” enough and with enough consonants to trigger the VOX and keep it open: perhaps because of my prior ham radio experience, it wasn’t an issue for me. I believe, but have no data to support this belief, that one of the reasons things continue to improve is her increasing ability to accomplish these tasks.

4. Adding Radios.

    • a) Selection.

      • Now it got a bit more complicated. The US Autocom distributor sells several Motorola hand-held transceivers, but feeling adventuresome (and being foolish, as it turned out), I poked around in the marketplace for something else. I bought a pair of UHF (smaller antennas and a bit less noise than VHF, at the cost of lower range) transceivers manufactured by Ritron, Inc., of Carmel, Indiana. They were quite small, sturdy and well-featured, and I thought they’d be easier to mount on the bikes.

For UHF use at the 2-watt power levels provided by these units, the main operator needs an FCC license in the General Mobile Radio Service. Take a deep breath before you complete the application: the tone of the required documents is set by the FCC remittance advice form. (This is like the remittance form which the IRS now requires when you send a check with your Form 1040.) The FCC remittance advice form is a whole page; the instructions for that form alone are four pages long. I’m a lawyer, I do forms and writing detail pretty well, and it was still hard. There are some other radio services (Citizens’ Band, and the Family Radio Service) for which licenses are not required. Ham radios require all operators to be licensed. (The Motorola radios, of which more later, came with an application and good non-government instructions.)

The GMRS license authorizes use of a specific frequency (or two), as well as the use of five “standard” frequencies. Some radios (like the Ritrons) are set up for specific frequencies and only the dealers and manufacturers can change them. Others, such as the Motorolas discussed below, have switches to select various frequencies. The frequencies available vary model by model. When applying for your license, it would be most prudent to request a frequency which you know can be handled by the transceiver you wish to use, and which isn’t in use in the area in which you plan to ride.

b) First set-up and test.

      • Bike-to-bike requires that each bike have a transceiver and an Autocom to control it. We wanted hands-free operation, where the Autocom’s VOX circuit would control the radio’s PTT (push-to-talk) function. Autocom sells appropriate connector cables for many radios and cellular telephones; I was put off by the $70/cable price tag, and thought I could build my own.

Like other handheld transceivers, the Ritrons have a PTT button on the side. The PTT function can also be controlled electrically through a remote microphone/speaker with a press-to-talk switch (like you see on cops’ shoulders). Even though I was finally able secure a schematic diagram of the wiring of Ritron’s external microphone/speaker, I was unable to wire an appropriate cable to connect the Autocom to the radio, through which the Autocoms’ VOX circuit would trigger the Ritrons’ PTT function. I gave up and bought the cables from Autocom. Each cable has a 5-pin DIN plug for the Autocom on one end, and a single molded plug with both a 2.5 mm and a 3.5 mm prong for the transceiver on the other end.

Although the Ritrons worked excellently by themselves, they didn’t work well or dependably with the Autocoms. There was unacceptable feedback and inconsistent actuation. I tried everything I could think of, and eventually called the Autocom folks. They said they thought they could make a connection between the Ritrons and the Autocoms which would work – they had done so for other customers who had different model Ritrons – so I shipped the radios and intercoms and cables off to them.

The resulting news was again bad: they couldn’t make them work, either. The PTT/microphone circuit in the Ritrons I’d bought was apparently incompatible with the Autocom Pro3000. I either had to change the intercom or the radios. If I changed the intercoms and moved down to the EuroCom, new headsets would be required and I’d forego the AGC. On the other hand, if I wanted to keep the Pro3000 intercoms, I’d need other radios, such as the Motorolas distributed by Autocom. I elected to change the radios. This required different cables to connect the Autocom to the transceivers; the TopGear folks were again cooperative and took back the unusable Autocom/transceiver cables. As before, I paid for all the shipping.

The new radios came, and they worked. Whew. We must have looked pretty funny, walking around the neighborhood wearing helmets, and talking to one another.

c) First-time bike-set up.

      • Although we still had to be able to get to the controls of the radios to turn the radios off when we weren’t broadcasting, we didn’t need access to the controls while riding. I wanted all the electronics to be as inconspicuous as possible.

The first radio installations were different for each of our bikes. On Mary’s R65. the Autocom and the Motorola fit in the under-seat tray, wrapped in foam for some vibration insulation. The antenna pointed backward, through a hole in the rear of the tray, and extended next to the plastic rear fender.

The RSL was harder. While it might have been possible to put the radio up front under the fairing somewhere, it would have been impossible to get to the radio’s controls. The radio ended up in the tail cone, also wrapped in foam. It sat on the left side, with its antenna pointed forward, just inboard the left frame tube. It all fit easily under the rear seat.


5. General

    • The system worked, but not very well. Usually she could hear me, but sometimes she couldn’t, and sometimes she could hear my voice but it was garbled. Frequently I couldn’t hear her at all, and many times I could hear her transmitter activate, but hear no audio or only a word or two.

It was not an easy process to find and reduce the causes of these problems. There were many. For instance, a weak or broken signal might have been caused by poor RF propagation (due to antenna placement or bad connections) or by weak batteries in the Autocom or the transceiver – and any of these problems might exist in one or both bikes’ installations. Maybe I’m just not as bright or energetic as I once was (or think I once was), but it was a long and discouraging job. In retrospect, having a consistent source of power for all the electronics (discussed in Section 7, below) turned out to be a necessary prerequisite to killing the gremlins. I’d suggest that it makes sense to complete the power supply wiring, and make sure it is dependable and operational, before you begin debugging the rest of the system. As I mention elsewhere, it’s also likely that our increasing familiarity with the system contributed to it’s increasing success over time.

Although I’ve divided the discussion into “antenna” and “power supply” segments for clarity, most of this stuff was going on at once. It was much less clear when I was in the middle of it than it is now in retrospect.

Finally: the volume controls on the radios affect speaker volume on receive only, and then (because the Autocom apparently amplifies the signal given to it by the radio) only to a limited extend. The volume controls have no effect on the gain or modulation of the transmitted signal. I set these controls about the middle of their range. Other Autocom users have reported that if the radio’s volume control is set too high, the Autocom can misbehave and trigger its transmit function inadvertently.

6. Antenna Modifications

    • My original idea was to mount the radios under the bodywork, and have only the antennas – mounted remotely – showing up top. I worked very hard to accomplish this, using fittings available from Radio Shack which added BNC connectors to the tops of the radios, so coaxial cable (and remote antennas) could be connected. No matter what arrangement I tried using the stock “rubber ducky” antennas, there was some problem or problems which had the effect of attenuating the radios’ signals. Using remotely-mounted antennas, bike-to-bike communication was intermittent and inconsistent. It was so bad as to be unsatisfactory, and I was seriously discouraged.

Then I decided I should try the system with the stock antennas mounted directly on the radios’ cases, where they were designed to be; perhaps something was awry in the connection between the radios and the lengths of coax, as things seemed to work much better in the garage tests when we held the radios in our hands with the antennas mounted right on their cases. I duct-taped the radios to the bikes to try it out and … the system *finally* worked well. I could now hear whole sentences! It worked like I thought it was supposed to. Perhaps the fittings (which enabled me to mount the antennas remotely) were some kind of impedance mismatch sufficient to reduce the radiated power substantially. But I don’t know for sure; Brian Curry suggested that the coax itself might be at fault; Gary Dallas thought that the original radio designers might have consciously made it electrically inefficient to mount the antennas remotely, so as to discourage folks from tinkering with what aren’t supposed to be tinkerable radios.

What I then knew for sure was that I now had to figure out attractive, sturdy, and easily-removeable mounts to hold the Motorolas to the bikes, vertically and fairly high up. For Mary’s bike, an unfaired R65, this turns out to be a piece of sheet metal 2″ x 6″ x 1/16″, slotted to take two hose clamps which hold it to the handlebars. The radio’s standard belt clip holds the radio case to the sheet metal, the bottom of which is bent in a little lip to hold the bottom of the radio. A rubber band keeps things from vibrating.

While I was planning to do something similar on my R11RS (probably fastened to the grab rail at the rear of the seat, or perhaps to one of the rear faces of the saddlebags), Jey Yelland suggested I try a dipole antenna, rather than the stock rubber ducky, because the dipole would be electrically superior, and might more than make up for whatever losses were incurred by remote mounting. I still harbored dreams of a stealth installation, so I made a dipole to try. To do so at our frequency of 462 MHz, strip 14″ of insulation from the outside of a piece of coax, then push the shield back over the insulation on the standing part of the coax. Trim so that 11 3/4″ of center conductor shows, and make sure an equal length of shield extends back down the outside. Seal the ends. So I didn’t have to worry about installing a BNC connector, I used a 6-foot length of coax which came with connectors on both ends. I taped the finished antenna vertically inside the fairing.

One important change was the addition of a ground to the antenna connection. The antenna connection on these Motorla radios is a center conductor only; there’s no connection between the shield of the coax and the “-” pole of the transmitter output. The Radio Shack fitting (RSU 11437399) which permits using a BNC connector and an external antenna) can’t, therefore, make a ground connection. Adding such a connection was easy: I stripped back some of the insulation near the BNC connector, and soldered a wire to the coax shield. The other end of the wire connects to the radio’s ni-cad battery’s “-” pole, through the wiring (described in the next section) for keeping the ni-cad battery charged.

The dipole antenna on the RS turned out to work as well as, or better than, the stock rubber ducky mounted directly on the radio. So I could, after all, keep the “stealth” installation on the RS. I’d still like to have a hidden installation on the R65, but the antenna is a challenge. There’s no easy place to mount a coax dipole, especially when trying to avoid taping it to metal tubing. I may try a full-wave vertical (just under 12″) on the front fender, or on top of the headlight, or on a homemade bracket.

7. Power Supply Modifications

    • We had difficulties with batteries; it was all too easy to lose track of what was charged and what wasn’t. Things would seem to work in the garage, and then not work on the road. Batteries that looked good in the morning sometimes went flat real soon. I thought it would be a lot more dependable and much more elegant if all the new electronics got their juice from the bikes’ electrical systems, and we didn’t have to worry about replacing the internal batteries on the Autocoms and charging those in the Motorolas, and keeping track of it all.

The Autocom Pro3000 requires 9 volts. Autocom makes two power supplies, one for $75 which has a power take-off for a Walkman, and one for $55 without it. I don’t do Walkman, thought “volts is volts,” and bought two Radio Shack 270-1562 12 volt to 9 volt converters for seventeen bucks each.

The Motorolas’ batteries are labeled 7.5 volts, and depending upon their state of charge, deliver as much as 8.2 volts. The snap-in battery trays could take six Ni-Cads (which would deliver 7.2 volts) or six alkalines (which would total closer to 9 volts); the external battery charger is labeled 11 volts and I measured it delivering 15. The external charger is designed to work with the Ni-Cad installed in the Motorola, even while the radio is operating. It looked to me as if I could just connect the Motorola to the same 9v supply I’d bought for the Autocoms. I tried it. It worked.

Because I’d read that the Autocoms are sensitive to power level fluctuation (which can occur even with a healthy bike battery when power is borrowed from another circuit, such as a bike’s tail light wire), I decided to find some ignition-switched current, and use the switched current to control a relay; the relay secondary would connect bike battery voltage directly to the power converter. The power converter instructions caution the user to disconnect the converter when not in use, so for those many times when I’m riding by myself, I added a SPST switch to the circuit which controls the relay’s primary coil. On the RSL. the power converter is zip-tied to the top of the plastic air intake horn under the left-side of the fairing, and the relay (RS 275-226) is a few inches forward, fastened under a handy 10mm bolt. The SPST switch mounts in a hole on the forward face of the relay box at the right front corner, where it’s easily accessible when the seat is removed – which has to be done anyway to pull out the rider’s headset lead at the beginning of the day, or to stow it at the end. Using PageMaker, I made a stock-looking “Intercom and Relay Power” label for the fuse box lid.

Connecting the pieces was easy. Ignition-switched current (tapped off the front running light circuit) runs through the SPST switch to the relay’s primary coil, and then to ground. Battery current is fed directly into one of the relay’s switched contacts, out the other side of the relay to the primary side of the converter, and out the other side of the converter to ground. I soldered a pair of two-connector female connectors (RS 274-222) to the output of the converter.

A matching male connector was soldered to a two-snap battery connector (RS 270-324), which itself snaps directly to the Autocom’s 9 volt battery connector; a small hole in the battery cover allowed the wires out of the Autocom’s case.

Connecting power to the Motorolas was a bit more complicated: the Motorola’s power input socket is twinned with some of the microphone/spkr/PTT functions, and can’t be used when the Autocom connector cable is plugged in. The Motorolas have removable Ni-Cad batteries, whose connections are spring clips. I wanted to keep the Ni-Cads in place when the unit was in use. I stripped a few inches of insulation off the end of an appropriately-sized wire, and wrapped the stripped end of each wire around the appropriate spring clip, so that the wires would be pressed between the clips and the Ni-Cad. It turned out to be easy to solder the wires to the clips. I brought those two wires out of the radio case through small slots in the plastic cover (filed with a very small round file), to another two-pin female connector. Very thin strips of metal like shim stock might also work to make the battery connections, and might be thin enough to exit the transceiver case without having to file slots.

On the RS, the wires from the male side of the connector run from the tail cone (where the Motorola was located when I tried remote mounting of the antenna) forward to the power converter, where another connector plugs into the converter output; the power cable may therefore be disconnected at either or both ends of the system. Note that in order to prevent the Motorola’s Ni-Cad from discharging back through the converter when the converter isn’t providing power (that is, when the bike’s ignition is off or the SPST switch is open), you’ll need a diode between the converter and the Ni-Cad; the diode allows current to flow towards the Motorola, but prevents current from the Ni-Cad from flowing out to the converter. I used RS 276-1101, and put it in the + power wire between the Motorola’s ni-cad and the first two-pin connector.

The wiring on Mary’s bike was similar. I found ignition-switched power at one of the fuses, and brought it into the underseat tray through two pins of a four-connector plug-and-socket combination (RS 278-767), which is located just outside the front of the tray. The SPST switch is inside the tray, mounted through the top lip at the front; it is visible and available when the seat is raised. The power converter is zip-tied over the large opening in the electrical panel, under the right side of the fuel tank. The relay is next to the converter in another previously-empty mounting position in the panel; the relay secondary obtains 12v directly from the battery. The other two connectors of the four-connector plug carry the converter’s 9v output into and out of the underseat tray. The entire tray can be easily removed by disconnecting the antenna’s BNC connector and ground wire, and unplugging the four-connector plug.

(On the R65, I didn’t connect the converter power to the Motorola when it was mounted on the handlebar bracket, as it was just too many wires. I’m sure it could be done neatly, however, and if I can make and install an antenna which works well, then I’ll move the radio back under the seat and reconnect the converter power.)

When we first went out on a whole-day ride, the Ni-Cads in both radios were absolutely flat at the end of the day, as if they’d been drawn down excessively and not recharged at all. I was mystified. Back on the bench, I discovered that I’d installed the diodes in the wrong direction, which prevented the Ni-Cads from being charged by the power converter, and allowed them to discharge to ground as soon as the power converter was turned off. I reversed the diodes, and the radio batteries stayed charged.

Therefore, before you power up your new circuits:


Pay particular attention to the 9v snap connectors which bring juice to the Autocoms; on both bikes, the confusing logic dictated by the snaps made me want to wire them backwards.

Both the Autocom and Motorola can thus be powered by the bikes’ electrical systems. You wouldn’t need need to change or charge batteries. Using the bike’s electrical system, the rider’s obligations are to (1) Plug in the helmet cables and (2) Turn off the converters and the radios when not in use. As I mentioned earlier, having dependable power assists greatly in diagnosing what other ills may travail you.

7. Results and Thanks

    • This project seemed to take forever (and is still not completed, as I’m not finished with the R65 antenna) and was, for a while, quite discouraging. It now works quite well.

Generally speaking, in spite of the Autocom’s AGC, the lower the speed, the better the system works. Apparently because of the interaction between our helmets and our bikes windscreens, occasional combinations of bike speed and crosswinds cause the transmitters to actuate on their own. Closing the faceshield (which is hard on a very hot day) stops the self-actuation.

Range is sufficient for our purposes: generally several blocks in traffic, and a mile or more in the open. On the other hand, sometimes we can communicate when we’re out of sight of each other, and sometimes her audio drops out unexpectedly. On balance, it is a wonderful convenience, and I’m glad we have it.

On the UHF band, there is occasional interference from other users. These seem mostly to be business or commercial stations, and we find them rather entertaining. (If this became a problem, we could obtain CTSS subaudible tone calling for the radios; small plug-in CTSS circuit boards are available from Motorola and Radio Shack.)

The installation is very user-friendly: we don’t have to pay attention to the electronics during the day, but do have to turn things off at night, and (at least so far) remove the radio from the R65 and plug in the charger at the end of the day. None of the batteries should go flat unexpectedly. The electronics and wiring are not in the way.

The downside is price: the whole setup cost a bit more than $1200 – and I’m giving myself plenty of credit towards the Ritron handhelds which worked just fine, but not in this setup.

I received a lot of help and support from list members Roger Wiles, Scott Adams, Tom Austin, Jerry Cook, Karl Rosenblum, Phil Kolehmainen, Bill Champ, Anton Largiader, Brian Curry, Gary Dallas and Jey Yelland. Chris at TopGear Accessories, the Autocom distributor, was also helpful and of assistance. Thanks to each of you for your help and patience!

David Brick Santa Cruz CA BMW R11RSL RA MOA BOOF etc

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