Last Modified: December 11, 2011
Contents:Basics; Battery Monitoring Systems; Event Data Recorders; Code Readers; Data Corruption; RFI Egress; RFI Ingress; Electronic Engine Controllers; Data bus System; Conclusions;
From reading some on-line articles, you might be led to believe that installing amateur radio gear into a vehicle will void the warranty. Nothing could be further from the truth! In fact, if you believed some of the palaver, you wouldn't even use your cellphone!
From the onset, it is important to point out that RFI egress (interference from the on-board electronics) is much more sever than RFI ingress (to those same electronic devices). Based on this fact, it behooves all of us to keep abreast of what's happening with respect to on-board electronics. The reason will become apparent as you read on.
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 via data bus systems (see below). 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 are another example, and have become mandated on every vehicle (<12,000 pounds) sold in the United States (2012>). 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. Every one of these devices egress some level of RFI. And perhaps a few might be susceptible to RFI ingress, but as pointed out above, that's much less of a problem than it would first appear.
Due partly to meeting new fed mandated fuel economy standards, more, and more new vehicles are designed to shut off the engine when it isn't needed—at a stop light for example. Realizing that life doesn't stand still too, special devices are being installed which monitor the condition of the battery. If the battery isn't up to snuff, or the accessory load is such that the battery might not be able to restart the engine, the engine remains running.
Both the voltage, and the current draw from the battery are measured. The latter measurement incorporates a Hall device located very near the battery. In the case of Ford, and Nissan (et. al.), the Hall device is part of the negative battery connector. In addition to the BMS, most systems also incorporate a battery booster of sorts, to maintain the voltage level fed to the accessories like the Navi system, entertainment devices, and even the instrument cluster.
Battery Monitoring Systems have been with us for some time. BMW for example started using them way back in 2002. As they become more popular, we'll get a better view of their ability to handle the installation of amateur radio gear. Until that time, is behooves readers to peruse the Caveat section of the Wiring article.
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 latest iterations record all manner of data collected by the various on board devices. The latest versions are referred to as OBDII-EOBD, with the latter standing for Extended On-Board Diagnostics, and are required on all vehicle starting with the 2012 model year. There is even a new standard for non passenger vehicles, called HDOBD.
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 MIL (Maintenance Indicator Light), and can be retrieved using a code reader. The collected data on later versions includes, but isn't limited to, engine RPM, speed, cornering Gs, braking force, steering angle, throttle position, and temperature. All of the data are important when analyzing a crash scenario; the real reason for the data collection in the first place. In addition, manufacturers have their own set of parameters. For example, GM EDRs record instances of over revving which could cause severe engine damage, especially in high-performance vehicles like the Corvette, and Cadillac V series.
Probably the most insidious collected data is the last 30 seconds of cabin audio! While not universal (as of yet), it remains to be seen what the constitutional legality of this private intrusion may or may not be. But, it doesn't take a rocket scientist to see the implications if this data, if it were used in a law suit as a result of a crash.
While the various control CPUs may be all but bullet-proof RFI wise, all of the various on-board sensors are subject to excessive levels of common mode current, and ground loops. When they are affected, the MIL (Maintenance Indicator Light) may be illuminated. Dealerships charge an average of $50 to reset the MIL, and readout the codes. Code Readers are an inexpensive alternative than going to your dealer.
If you would like to read an overview of the history of OBD, here is a Wikipedia page covering the devices.
One way to know if you have corrupted data, other than the MIL, is to buy a code reader. Auto Zone, O'Reilly, Pet Boys, and others sell OBD II, and EOBD readers. Pricing, depending on the units reading capabilities, range from $29 to well over $200. They come with a book or CD-ROM listing all of the various error codes. Most can also turn off the light, and clear the memory. Considering the cost to have your dealer turn off the light, an OBD II-EOBD reader could be a bargain in the long run.
If you buy one, make sure it is capable of reading the EOBD (extended on-board diagnostic) codes, like the Autel AL510 shown at right. As alluded to above, all US vehicles must have EOBD by 2012, and this includes light and medium duty trucks, and SUVs.
By the way, as mandated by fed law, the code reader socket is located beneath the steering column. If it is not located at that spot, there must be a sticker telling you where it is located. This fact just proves how anal retentive fed thinking is!
Some automobile manufacturers password encode access to the extended data. Fortunately for most makes, a Google search will net you the password. Problem is, in too many cases you need a second password to reset the extended data. In some high-end units, the extended data cannot be erased, unless a code is sent to the unit via its navi or cellphone interface. Talk about Big Brother!
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.
It should be noted, that not all RFI-related data corruption will cause error codes to be written to the OBDII-EOBD. And, as mentioned above, RFI can play havoc with the individual data sensors connected to the various on-board electronic devices.
The one thing we'd all like to see, is an equal effort 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; 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.
One good aspect of mobile busing systems is the simple fact they're getting more complex in design, with much higher data handling capabilities. As a result, the digital noise they generate has to be better controlled. Read into this, less signal leakage in and out of the digital wiring. I think we all will welcome any reduction in the digital hash, and birdies generated by most of the current data bus systems.
RFI ingress can be annoying, but thankfully it is usually easy to cure. Sometimes a single bead will suffice, perhaps a bonding strap, and sometimes low-current wiring (i.e.: antenna motor control leads) 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 is egress, this article should help. If it is ingress, you already have the source, but perhaps not the cure.
As alluded to above, RFI ingress can cause sensors to send the wrong data back to their respective control devices. These may include, but aren't limited to, automatic braking systems, automatic transmission controls, electric power steering controls, and vehicle stability systems. If for any reason you experience issues with any of these, you should stop transmitting immediately! The next step is to cure the RFI ingress. This may require changing the antenna mounting methodology and/or location, installing more adequate wiring, doing additional bonding, additional choking impedance to the antenna's motor control leads, and better common mode current suppression to the coax cabling.
If you own a late-model vehicle, you need to be aware of the following. They all use their EEC (Electronic Engine Control) to monitor the alternator's voltage and current. These readings (in part) help control the fuel injector timing, hence the mixture, which also improves gas mileage. As a result, at slow engine speeds, when the alternator is under a varying heavy load (amplifier use for example), the engine may hunt (stumble and misfire). In some cases, this will cause an error code to be sent to the OBD II which turns on the MIL (Maintenance Indicator Light).
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.
In some cases, the data error 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 MIL isn't on, there may very well be stored error codes! Some of these may not be amateur radio related, and could indicate an actual problem.
The OEM alternators on most of the newer model vehicles utilize a double wound field coil replete with 12 diodes. For example, the Honda Ridgeline comes equipped with an 130 amp alternator that is physically smaller than Honda's old-style 6 diode 105 amp unit. All Honda vehicles now come with this type of alternator (except the hybrids of course), as do most other makes, and models. Fact is, a couple of large SUVs come with 250 amp, 12 diode alternators, but you can't tell from their size. All of this upgrading in amperage is a good thing for us mobile operators. More information is in the Alternator article.
Modern EECs are what allows late-model, high-powered vehicles to achieve almost unheard of mileage ratings. One of the strategies used is ELD (Electrical Load Detection). Any load applied to the electrical system will be measured, and the requisite changes in engine settings to match that load will be adjusted. Although they work well for most automotive needs, imposing SSB, and its ever-changing power needs, often overtax EEC systems. This may cause engine stumbling, or erratic shifting patterns as the ECC tries to compensate for the rapidly changing load. Whether this causes the MIL to illuminate is perhaps moot, but it can be scary to the neophyte.
The OBD II, along with the various on-board ECUs (often called FRED or Frustrating Ridiculous Electronic Device), use ISO-defined networking to transfer data between them. This eliminates redundant signal paths, and allows sharing of the various sensors. More and more new vehicles are being equipped with data bus systems. They're commonly called CAN (Controller Area Network) or BEN (Body Electronic Area Network). 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, so FRED's digital voice is easily heard.
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.
I should mention that some vehicle computer systems use a color burst crystal as an oscillator (3.579545 MHz). The 41st harmonic is 146.76134 MHz, which causes problems with the 146.16/76 repeater pair. However, component tolerances can cause the harmonic to be anyplace between about 146.70 MHz, to as high as 146.80 MHz. In my Honda Ridgeline, the actual birdie is not stable, and varies due to temperature.
The worst birdie 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. It should be noted, that other manufacturers use Toyota's SynergyDrive® system, and in most cases, just as RFI noisy. Oddly enough, Honda's hybrid is just slightly noisier than a standard drive train, so there is hope!
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 cognizant 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.