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Auto Manufacturer’s Policies

By Ed Hare, W1RFI, ARRL Laboratory Supervisor

Installing mobile radios in your new megabucks car can be a frightening proposition - especially if RF from your rig could damage your shiny new roadster, voiding the warranty! Want help? Read on!

In the good old days, things were simple. If you wanted to install a mobile radio in your car, your primary considerations were mechanical: where to place the antenna, where to mount the radio and how to route the wires so they didn't interfere with the family use of the car.

There were some incompatibility problems to solve, such as electrical RF noise from the ignition system, but the proper application of cures (resistive wires and plugs, or, in extreme cases, a filter for the distributor and its wiring) almost always resulted in a successful installation.

As automotive designs evolved, however, installing mobile radio systems became more complicated. Remember how computers used to be house-sized monoliths? In the early 1980s, microprocessors and their associated circuitry became small enough (and inexpensive enough) so car manufacturers (and many others) could use them to control many different functions.

In the early 1980s, electronic control modules (ECMs) became standard in most cars. There were sporadic reports of interference problems to and from these devices, but most hams were able to find a work-around. Soon it became possible to use microprocessors to accomplish additional automotive functions, ranging from engine control to anti-lock braking to air-bag deployment. Some manufacturers even use "slave" microprocessors to control things such as rear-end lights, running only one cable to the back instead of an entire wiring harness, using the "slave" microprocessor to execute proper tail-light sequence (brakes, signaling, etc).

Sure enough, these electronic marvels came with a price! The more complex things become, the more likely it is that things will go wrong.

Every microprocessor has a clock oscillator, and the circuitry uses digital signals for processing and control. These digital signals are square waves. They're perfect for digital circuits, but rich in harmonics.

FCC regulations (Part 15) specify the amount of interference that can be generated by these "unintentional radiators." The regulations are adequate to protect other radio services, such as TV reception in nearby homes, but they're not intended to protect against interference to radio receivers installed in the vehicles, broadcast band or otherwise.

In addition, the vehicle electronics can also be affected by strong electromagnetic fields (EMFs). These fields can be caused by nearby transmitters, transmitters installed in the vehicle, high-voltage power lines, and so on.

Most manufacturers created electromagnetic compatibility (EMC) departments to deal with testing and design issues, assuring compliance with federal regulations and compatibility with factory-installed equipment.

In addition, the industry has voluntarily developed standards that apply to many EMC technical issues (see the sidebar on the Society of Automotive Engineers). There is even a standard that applies to installed transceiver equipment. (The ARRL is a voting member of the SAE Committee working on these standards.)

So far, things look pretty good! New technology has made cars less expensive, more reliable and less polluting. Federal regulations control the amount of interference that cars can generate, automobile manufacturers have created departments to solve the problems and the entire industry has formed committees and developed standards to help make things right.

As automotive designs evolved, ham gear did, too. More and more ham transceivers were capable of operating from a 12 to 14-volt supply, so mobile operation became more popular than ever.

Unfortunately, this rosy picture was spoiled by an unexpected phenomenon; radio transmitting equipment, sensitive receivers and automotive electronics didn't always work well together.

As if this weren't bad enough, EMC problems usually take place on a two-way street (all puns intended). Just as vehicle electronics can interfere with installed radio equipment, even low-power transmitters can interfere with vehicle electronics.

Details are not forthcoming, but urban legends abound about vehicles that would stall or lock their brakes near high-power transmitters, or about hams who could stall nearby vehicles on the highway by keying up high-power transmitters. (The ARRL staff has amassed a fair collection of anecdotal reports, none of which describe this problem firsthand.)

The legends may or may not be true, but vehicle manufacturers know that fields of up to 300 V/meter can be found on our highways and byways; automobile electronics must continue to function when drivers whiz past Voice of America transmitter sites!

Car companies have worked to ensure that their vehicles do not interfere with factory-installed equipment and do not keel over near VOA-class transmitters, but it's clear that manufacturers do not always pay attention to compatibility with after market equipment, including transmitters and receivers for various radio services.

When hams installed transceivers in their cars, things didn't always work as planned. As the number of automotive microprocessors grew, the potential for the umpteenth harmonic of the clock oscillator falling on a favorite repeater channel also grew. Add to this the possibility of noise from sophisticated ignition systems, motor noise from wiper-blade, electric cooling fan or fuel-pump motors, and even the vehicle's factory-installed broadcast-band radio receivers and you have a potential for electromagnetic incompatibility.

What's worse, some vehicle electronics are susceptible to RF fields generated by mobile transceivers. This susceptibility ranges from the minor annoyance of having a dash light come on in step with the transmitter, to the major annoyance of having the vehicle's microprocessor lose its mind, resulting in a dead car.

The ARRL has not received any reports about interference to safety devices such as anti-lock brakes or air bags, but this type of interference is still possible, especially if good installation techniques are not used.

Wheels Start to Turn

In early 1992, John Harman, W8JBH, wrote an item for QST's Correspondence column pointing out the problems he was experiencing in trying to get Toyota to help him with an interference problem he was having with his 1992 Camry.[1]

In Harman's case, his 2-meter transceiver had resulted in temporary damage to the car's ECM. John, as of that date, had been unable to get any concrete information from Toyota about the proper installation of transmitting equipment in his vehicle.

Since then, we've heard from other hams who experienced similar interference. The May 1992 issue included a few more tales of woe. In addition, the ARRL Technical Information Service and RFI Desk heard from a few dozen folks who had been having some sort of EMC problems with their cars, dealers or manufacturers.

This is, of course, just the tip of the iceberg; most hams simply do not report their interference problems: not to the FCC, the involved manufacturers or the ARRL.

The situation was confusing. After hearing tales of blown ECMs and voided warranties, hams were afraid to install mobile transceivers in their cars. As interference reports increased, the Lab decided to look into the matter.

ARRL Surveys Auto Manufacturers

As ARRL Senior Lab Engineer and all-round EMC guru, the task fell into my lap. "No problem!" I said. "We can ask car manufacturers to tell us all about their cars and policies." I drafted a letter asking the following questions:

·"How does your company resolve electromagnetic compatibility (EMC) problems that result from installed (or nearby) transmitter operation, or when vehicle electronics cause interference to installed (or nearby) radio receivers?"

·"Have you published any service bulletins that relate to radio transmission or reception, or electromagnetic interference (EMI)?"

·"If customers have problems with EMC or EMI that cannot be resolved by the dealer, who should the dealer or customer contact for additional assistance? Have these contact people been specifically trained in EMC and EMI mitigation?"

·"May we make the information you provide available to our members?"

We also outlined some typical Amateur Radio installations, citing power levels of 100W on HF, 50W on VHF and 10W on UHF.

I sat back and waited for a flood of responses from a field of eager manufacturers. I knew that each would tell me that it was okay to put transmitters in their cars and that if hams had problems, dealers and customer service people would be glad to help them out.

The replies would lead to an article summarizing the responses that would clearly explain how to install a radio in each type of car and reap the praise from all of our grateful members. NOT! (Well, not exactly, anyway.)

After 60 days, we'd heard from only a handful of manufacturers. The first round of responses didn't look very useful, with the letters ranging from "We have never had a problem with radio installations," to "It's not our fault - ever!" The latter is paraphrased, but not too far off the mark.

Things weren't going to be as smooth as I had hoped. I waited impatiently another month and sent off a follow-up letter, asking what happened to the first letter, and pointing out how the manufacturer was going to look if it did not respond and were listed in a national magazine as having ignored two letters.

Over the next 90 days, the answers trickled in. In many of the letters I could clearly see the mark of the manufacturer's marketing, public relations and legal departments. The caveats were rampant, and in most of the letters the disclaimer that if any after market equipment, including radio transmitters, caused any damage to the vehicle would not be covered under warranty.

One company said the answers to the questions I had asked were proprietary! Even worse, some companies didn't respond at all! In most cases, I finally got a response by calling the respective public relations departments.

To partially offset the number of companies that didn't respond, one company sent two answers - completely contradictory, of course. The mix-up was ultimately resolved, but it demonstrates that a big part of the EMC problem may involve poor communication.

A company can have an excellent EMC facility, program and policy, but if its information isn't widely distributed to dealers and regional offices, it does little good.

If QST received contradictory responses from the same building within the same company, imagine how difficult it could be to get accurate information from corporate and engineering policy makers at the factory to dealers who have to actually solve the problems.

So far, the overall manufacturers' response hasn't been that good. It isn't all bad, however. I noticed several call signs in the signatures of the letters I received. Not surprisingly, these were among the more useful answers.

A few of the companies came quite close to my ideal, giving us solid information and telling us that their dealer-support network or factory specialists will help hams with compatibility problems!

Toyota, the company whose customer really started the ball rolling, did respond after much prompting (not unlike John Harman's experience). And after all was said and done, Toyota's response was actually positive. It took a bit of time, but for the 1994 models, the 10-W power output limitation mentioned in the 1992 Service Manual has been upped to 100 W. According to Toyota's Customer Service Department, a few of the 1994 manuals were not updated, but the current limitation of 100 W applies across the board.

General Motors has long been proactive in the EMC field, maintaining a complete EMC facility (like many other automobile manufacturers), publishing a complete and useful installation guide and maintaining a high profile in the professional and amateur EMC press.

Even more encouraging is the fact that several companies told me privately that my letter and article have prompted them to develop their own EMC guidelines and to clarify company policies about EMC.

Unfortunately, there have been problems even with some of the companies that have clear policies and installation guidelines. In several cases, hams who have reported problems tell us that customer-service people or dealers made decisions that were different from the information that we received in writing from the manufacturer.

When I called the Customer Assistance Center at Pontiac, as a follow-up to Member who called me, at first I was told the same thing as the Member - that they had no information about how to install radios in cars. Everyone I spoke with at the assistance center insisted that the dealer is the only source of information.

Remember, GM is one of the good guys! They have an active EMC department, published installation guidelines and clear policies. Unfortunately, the process often breaks down.

All in all, the problems are not surprising. Many auto manufacturers are giants, and it must be difficult to maintain a clear policy in all areas across such a diverse and spread-out business structure. On the other hand, our original letters were sent directly to each company's customer-service contact address.

Of course, all of the policies could be swept away by the new model year! As each new model is designed and built, its EMI susceptibility presumably will be different than its predecessor. Because most manufacturers won't guarantee that a properly installed transceiver will not interfere with a vehicle's proper performance, we could never keep track of the changing policies and applications.

Clearly, manufacturers have a way to go before the policies and standards formulated by their hard-working EMC engineers and EMC committees can make a difference for the average ham. The ARRL will continue to work toward that goal - and you can help! If you've had interference problems with your automobiles, or good or bad experiences with your dealer in getting those problems resolved, report this to the manufacturer at the address we list at the end of the article. This will help manufacturers to stay on top of the types of problems their customers are experiencing.

Send a copy of your letter to:
ARRL Headquarters
RFI Desk
225 Main St.
Newington, CT 06111-1494.

I will collect the letters, combine them with what we already have, and send them en masse to the key players at automobile manufacturers and their standards committees.

Let's see how we can make a difference. If all else fails, contact Mike Gruber, W1MG at HQ with your automotive EMC problems. His email address is  


What the Manufacturers Say

Now, as promised, a description of each manufacturer's policy statement. The addresses and telephone numbers are the manufacturers' suggested contacts or are the addresses on the letterheads of the letters we received from manufacturers. All of this information is based on the statements made by the vehicle manufacturers. Manufacturers not listed were not contacted. If the manufacturer answered our question about who to contact to resolve problems, we have included that in their response. If not, contact your dealer or the manufacturer's customer-assistance network. Most manufacturers suggest that customers contact their dealers, who have access to the normal problem-resolution workers through zone or regional offices, which, in turn, contact the factory for support with difficult problems.


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