On Feb 12, 5:17 pm, "KE5MBX" wrote:
Hi,
What's all this business I hear people talking about blasting people's
car stereos or killing cars altogether with high-power RF?

Seems reasonable that high intensity RF could incapacitate the modern
electronics that control your average car these days. Put enough RF
at the right frequency in the right place and you can disrupt just
about anything. I'd bet that the stories are based somewhat in truth.

However, the question of "how much" would it take would not be easy to
answer. I've heard that 2 meter communications at reasonable power
levels would cause specific models to stop running, but I've not seen
it myself. I suppose that it would be likely that high power
communications could draw too much current and cause the battery
voltage to dip below minimum levels required to keep the car running
(with a week battery and low alternator output) and folks could be
confused as to what actually happened... But we are talking theory....

I currently can run just south of 50W on 2 Meters in my 93 Jeep grand
Cherokee and only rarely have issues with the audio system. I can
desense the receiver when transmitting at high power, but that is not
surprising as the two antennas are about 2 foot apart and run parallel
for most of the 2M antenna. I cannot imagine how much RF I'm pushing
into the poor car's stereo. I've had no permanent damage to the
stereo. I can usually drop back to 5 watts and keep talking w/o any
issues so I assume I'm not causing others issues. The car keeps
running (well as best as can be expected for something with 160K
miles) on either power setting. I've also put this setup in a 2001
Ford Expedition and have had no issues with the stereo as of yet, but
the antennas in this situation are separated vertically so I would
assume the isolation is much better.

I'd bet that if you keep your RF field strengths under the FCC
specified limits in the cars around you, and your car keeps running,
you won't cause anybody else permanente problems. Car designers have
to deal with possible situations where RF field strengths are very
high (like when you drive past a broadcast transmission tower) so I'm
sure they've designed and tested their stuff to make sure it survives
these situations. If you stay within the FCC rules on field strengths
I'd wager that nothing serious is going to happen to somebody else's
car.

You may cause yourself issues, but I doubt you will cause any
permanent damage. If you do have issues (the car stops running or the
stereo makes strange noises when you transmit) there are ways to deal
with that stuff and I'd cross that bridge when you get to it.

-= Bob =-