Digital Electronics
Last Modified: Tue, Oct 30, 2007
Some of the following information could be misinterpreted to suggest that amateur radio and automobiles are mutually exclusive. Nothing could be further from the truth. It's a given that some vehicles are worse than others with respect to RFI, both ingress and egress, but that fact in itself doesn't make them mutually exclusive. I've had a couple of vehicles which I was convinced were made someplace very hot, but in the end I won out.
Digital electronics have become so pervasive in modern vehicles, it is impossible to buy one without four or more factory installed digital processors. Known as ECUs (Electronic Control Units), they control every facet of a vehicle. Be that engine operation; standard and satellite radios; climate control systems; anti-lock brakes; vehicle stability systems; hybrid vehicle controllers; navigation systems; and supplemental restraints (so called air bags). More and more, these devices are being networked together. A good example of this is the integrated, voice commanded, Navi-Satellite-Climate control system made by Alpine Electronics available in Acura and Honda vehicles.
Anti-lock braking and vehicle stability systems is another example. In fact, in the not to distant future, integrated anti-lock-stability devices will become mandated on every vehicle sold in the United States. The rational is based on crash studies made by the NHTSA (Nation Highway Traffic Safety Administration), and the NTSB (National Transportation Safety Board), which prove their worth in saving lives. Independent studies by the ARC Network also bare out the results of the studies.
What all of this means is, there is going to be an ever-increasing number of on-board digital electronic devices in our vehicles. Devices, incidentally, that radiate RFI, and may be susceptible to interference by amateur radio transmitters.
Known as EDRs (and facetiously as black boxes), these devices record specific data which can be retrieved later. A good example is the OBD II (On-Board Diagnostic, level two), which has been mandated on every vehicle sold in the United States since 1996. The OBD II, along with the various on-board ECUs, use ISO-defined networking to transfer data between them. This eliminates redundant signal paths, and allows sharing of the various sensors.
Heretofore, the OBD II recorded mostly engine functions, such as misfires, inoperative devices, or sensor failures. The various codes are stored, which may or may not turn on the check engine light, and are retrieved using a code reader. Code readers come in plain Jane and fancy versions, and range in cost from $29 to as much as $200. They're available from most auto parts stores. Mobile operators would be wise to carry one with them, as RFI ingress is becoming more profound as the number of ECUs and sensors abound.
Some manufacturers, GM in particularly, started to record other data not directly related to the engine, or its pollution controls. Ford stores their data in the PCM (Powertrain Control Module). As a result, the state of California passed a law mandating that consumers be notified at the point of sale, if the vehicle has an on-board EDR. Federally, the notification mandate takes effect in 2008.
The fed mandate also states: ...that 15 essential data elements and up to 30 additional elements if the vehicle is equipped to record these elements. Included, but not limited to, speed, time of airbag deployment, change in speed, seat belt status, brake status, engine throttle position, and steering angle. The aforementioned GM system also records top speed, highest engine RPM, cornering Gs, which gear the transmission is in, non-activation of vehicle stability and traction control systems, and even the number of occupants. If things aren't bad enough, devices which read this data can be purchased over the Internet, opening up yet another bag of worms.
There is another side of this that could effect amateur radio operators both directly, and indirectly. And that is, corruption of the stored data.
Every mobile operator has, or has had, instances of both RFI ingress and egress. For example, ignition noise is a pervasive egressed RFI we all have to deal with. However, some forms of ingress may not be pervasive enough to be noticed. For example, modern speedometers use solid state electronics to store the mileage in a form which cannot be "rolled-back" by unscrupulous mechanics. However, the trip data is typically stored by volatile memory. If you disconnect the battery, the data goes away. RFI ingress can also corrupt this data.
On several occasions, I have corrupted my Honda Ridgeline's trip data. In all cases, the leading digit changed. This has only happened while I was operating on 15 meters, which brings up an important point. To wit; RFI ingress and egress have different effects (or lack there of) at different frequencies. You might not have any RFI problems on 20 meters, but that doesn't mean you won't have them on some other band.
Automobile manufacturers do a very creditable job of bullet proofing their electronics against RFI ingress. Ford Motor Company is a prime example. They thoroughly test their electronics, and they even support a web site for what they call Electromagnetic Compatibility (EMC). Although aimed at OEM suppliers, the data presented can certainly be of interest to any amateur radio operator with an RFI ingress problem.
The one thing we'd all like to see, is an equal effect directed toward reducing RFI egress. Of particular importance are those associated with the control electronics in hybrid vehicles, as owners of Toyota's Prius can attest to. Some are so RFI noisy, their AM radios are nearly useless in low signal areas. Adding some insult, are COP ignition systems. While later model units have lower RFI levels than earlier models exhibited, they're far from ideal. As a whole, automobile electronics are a major contributor to the overall background hash we all have to endure.
Fuel injection systems are yet another bothersome source of RFI egress. The latest iterations spray the fuel directly into the chamber (rather than in the intake manifold airstream), and use very high pressure to do so. This requires the injector solenoids to be somewhat more powerful than earlier systems, so the resulting EMI (electromagnetic impulse) is much greater.
One unfortunate fact is, automobile manufacturers are exempt from the FCC's Part 15 (Section 15.103, Exempted devices). While there are suggestions that the exempted devices should meet certain radiation levels, the fact remains they are exempt. Until the rules change (not in the foreseeable future), we're all going to continue to suffer ever-increasing levels of RFI egress.
RFI ingress can be annoying, but thankfully it's usually easy to cure. Sometimes a single bead will suffice, perhaps a bonding strap, and sometimes low-current wiring will have to be shielded. One very important thing to keep in mind; for any given RFI problem, what worked on your last install, might not work on this one.
Regardless whether the RFI problem is egress or ingress, the first step is to identify the source. If it's egress, this article should help. If it's ingress, you already have to source, but perhaps not the cure. Just remember, proper wiring and bonding are important.
If you own a Honda product (including Acura, as well as Toyotas, Isuzus, and Kias) you need to be aware of the following. They all use the EEC to monitor the alternator's voltage and current. It uses these readings (in part) to control the fuel injector timing. Replacing the alternator with an after-market one will result in reduced gas mileage. This fact also causes the fuel injection system to richen up the mixture if heavy loads (amplifier use) are imposed on the alternator. At slow speeds this will cause the engine to hunt (stumble and misfire), and in some cases cause an error code to be sent to the OBD II which turns on the Check Engine light.
Digressing; RFI ingress can also cause this problem, if the level is high enough to interfere with any of the various sensors feeding the EEC, or the EEC itself. If this is your problem, you might want to visit my Split Beads article.
If your Check Engine light turns on, don't panic! Auto Zone, Checkers, and others sell OBD II readers ($29 to $200+ depending on capabilities). They come with a book or CD-ROM listing all of the various error codes. They can also turn off the light and clear the memory as well. Most dealers charge between $50 and $100 to reset the light, so an OBD II reader is a bargain in the long run.
In some cases, the codes can tell you where to install RFI suppression beads. One of the codes I was seeing related to the throttle position sensor. I installed a bead on its wiring harness, and that particular code hasn't reappeared. By the way, just because the Check Engine light isn't on, there may very well be stored codes. Some of these may not be amateur radio related, and could indicate an actual problem.
Some newer OBD II units (primarily GM) store other data that may or may not be erased by the reader. These include the fastest speed you have driven, transmission parameters, and even the rev limiter readings. One major car company has used the special (non government dictated) codes to deny warranty service to those who have abused their vehicles. Whether this could be applied to codes tripped by RFI remains to be seen.
One last comment with respect to Honda alternators. Most of the newer models use a double wound field coil replete with 12 diodes. For example, the new Ridgeline comes equipped with an 130 amp alternator that is physically smaller than Honda's 6 diode 105 amp unit. I've been told that all Honda vehicles now come with this type of alternator (except the hybrids of course). At least that is one good attribute for us mobile operators.
More and more new vehicles are being equipped with data buss systems. Honda calls theirs MICS (Multiplex Integrated Control System). These systems are used to communicate data between the various on-board CPUs. From seat belt reminders, to door ajar warnings, and a myriad of others, their digital voice is is easily heard.
For example, the Honda system uses three different frequencies (10.4 kbps, 33.33 kbps, and 500 kbps). These signals mix and produce birdies up and down the amateur spectrum. My Ridgeline has birdies every 5 kHz that are audible from 80 through 15 meters. They are there higher up, but are slightly less bothersome.
The worst offender is the Toyota Prius. The control birdies, along with its digital control circuitry, virtually wipe out the HF and low VHF spectrum. If you own one, or are think about buying one, and intend to operate HF mobile, you're in for a very rude awakening.
The really bad news is, manufacturers will not address any concern whatsoever, with respect to these spurious signals. Remember, they are exempt under FCC rules.
First, we need to remain cognisant of the happenings within the NHTSA, the NTSB, and the automobile industry with respect to EDRs and their possible ramifications. This includes, but is not limited to, what might happen if you have crash, the EDR is corrupted because of RFI ingress, and you're held responsible.
Two, we all should keep the RFI problems we encounter in front of the respective automobile dealers. While most echo the manufacturers sentiments (our vehicles weren't designed for amateur radio), the squeaking wheel will eventually filter up the chain.
Lastly, do yourself a favor by keeping informed. Reading the auto section of your local newspaper, and by subscribing to a good automobile related magazine like AutoWeek are a good start.