Radios and Vehicle Systems Interference?

[Llwellyn]

Has anyone seen or heard about any installed mobile radio equipment interfering with the control or safety systems of any vehicle?

I just bought a new car, and every single place they talk about the airbag systems, they warn not to install any two-way radios in the car because they may interfere with the airbag and seatbelt pretensioner sensors, causing them to possibly not deploy when they are needed.

I'm just wondering how likely this scenario is... and I'm figuring the safety risk is pretty nil with a scanner vs. a transmitter as well.

They also mentioned about 100 places in the vehicle not to place objects or install anything... I'm trying to find a spot in the car that the antenna cables can actually go without becoming a hazard.

 

[N1508J]

It is possible!

Has anyone seen or heard about any installed mobile radio equipment interfering with the control or safety systems of any vehicle?

I just bought a new car, and every single place they talk about the airbag systems, they warn not to install any two-way radios in the car because they may interfere with the airbag and seatbelt pretensioner sensors, causing them to possibly not deploy when they are needed.

I'm just wondering how likely this scenario is... and I'm figuring the safety risk is pretty nil with a scanner vs. a transmitter as well.

They also mentioned about 100 places in the vehicle not to place objects or install anything... I'm trying to find a spot in the car that the antenna cables can actually go without becoming a hazard.

I have heard and experienced the effect myself. In particular, cruise control in my old Aerostar at times would "modulate" in speed or disengage. I was operating in the 30 to 40 MHz business band at that time low power (25 watt fm). Got rid of the problem with ferrite beads and .01's on the power input to the cruise control. With all the computer krap in the new "horseless carriages" these days, and the varied freqs and power levels we use, its gona be a bear to filter everything!

As said, your biggest concern is the airbags, next to them would be any system controlling fuel flow (if any).

If your vehicles body is non metallic, then you have a mess on your hands as well as antenna problems.

At any rate, should you decide to install a transmitter, locate the antenna as far away from the computer as you can. It most likely won’t make much difference due to all the wiring picking up your signal, but try it anyway.

Any monitor radio (scanner) receivers are not cause for concern. Your biggest problem is trying to find a location to mount it.

 

[n8emr]

MOST cars have a 2way radio clause in the. basically saying not to use them unless the are professionally installed. With all the computers and now airbags everywhere its more of an issue.

THere is a lot of CYA in the manual saying no 2 way radio, there is also some issues as well. Putting the antenna as far a away as you can is of minimal help if your coax goes right next to the computer. Best bet is to keep all RF away from the front and use remove head radios, put the RF as far away from the computers as possible.

 

[N1508J]

Agree in part, however...

MOST cars have a 2way radio clause in the. basically saying not to use them unless the are professionally installed. With all the computers and now airbags everywhere its more of an issue.

THere is a lot of CYA in the manual saying no 2 way radio, there is also some issues as well. Putting the antenna as far a away as you can is of minimal help if your coax goes right next to the computer. Best bet is to keep all RF away from the front and use remove head radios, put the RF as far away from the computers as possible.

While most of statement is great advice, running coax next to the computer, if unavoidable, should be no problem IF the cable is of good quality. Using coax with shielding of 80% is lossy (garbage). Considering the computer is fairly well shielded in its metal enclosure and perhaps RF grounded (?????), it may not radiate harmonics into the coax. More plausible, is the harmonic trash being radiated into your antenna emitted from the power and control wires entering and exiting the computer.

When transmitting, lossy coax can radiate (especially in poor swr conditions) into control wires to and from the computer thus confusing it during your transmission. It’s best to use low loss double shielded coax even for short mobile runs. If used, the outer shield should be tied to a GOOD RF ground at the transmitter and computer if possible. The other end should be left OPEN at the antenna. The inner shield is treated normally.

Finally, a less likely scenario involves the squibs used to initiate the charge for air bags. While having some EMI filtering protection, in the UHF bands there could exist a condition when the length of the squib leads become a quarter wavelength of an 800MHz transmitted frequency, whereupon enough energy may be developed across the squib for initiation. The use of high power is most likely the best causative factor to generate sufficient energy. That’s a highly improbable but not impossible outcome.

 

[gmclam]

Installing a receiver or transmittter?

You are certainly going to have more problems from a TRANSMITTER than you are a RECEIVER. Generally speaking, there should be little concern from connecting a receiver in an auto. If the auto electronics are so sensitive that a nearby RF signal from a receiver interferes with them; there is a huge problem. Of course that doesn't mean that auto manufacturers are doing a good job (in this area).

My thoughts include using good quality equipment; nothing modified. Use good quality coax, not the cheap lossy stuff. Use common sense when installing; for example don't piggyback power to your radio from some auto electronics device - run your own direct power. Again do not undersize the wire. Earlier posts about adding ferrite beads or small capacitors (or complete filters) is a great idea.

And lastly; from what I've seen, the so-called "professional installers" are usualy far more ignorant on this topic than us old time radio geeks.

 

[52to12]

I purchased a 2007 toyota highlander a couple of months ago. Neither the cigarett lighter or the 2 auxilary power outlets has power when the ignition is off. I asked the Toyota service mgr. if there was any place to tap into for continous power.He told me to run a wire directly from the battery and not to tap into any wires or to use a blank position in the fuse panel.He reminded me that any damage caused by tapping into the electrical system would not be covered by the warranty and would be very expensive to repair.