On 12 Feb 2007 15:17:37 -0800, "KE5MBX" wrote
in . com:

Hi,
What's all this business I hear people talking about blasting people's
car stereos or killing cars altogether with high-power RF? I run 2m,
10m, and 11m in my jeep and I'd like to sort out the fact from the
legend and find out what kind of power I can use without risking
damage to my jeep or cars around me. At what power level is front-end
overload to a nearby radio likely? At what power level is damage
likely, and to what componets?


Ok, this is a bit long:

Most of the newer instrument clusters (circa '90 and later) are really
sensitive to both static -and- RF, and are -not- shielded. Some engine
computers are also sensitive to RF (screws with the high-impedance
signal from the oxygen sensor). Even some anti-lock brake modules can
be disrupted by a strong signal.

Begin rant:

The SAE sure had its head up its ass when they allowed junk like that
to be made. Very few of these systems (if any) were ever recalled
because it is almost impossible to prove liability in any case of
failure due to RF. And the US Supreme Court ruled recently that a few
"accidental" deaths are an acceptable risk in corporate business
practices, releasing auto makers from liability for unsafe vehicles
provided that the problem is fixed after being discovered. Therefore,
new auto systems are tested for safety by the consumers who buy new
vehicles -- a system is proven "safe" if it doesn't cause any
financial liability (i.e, injuries and/or fatalities directly
attributable to the faulty system). One would hope that there is some
sort of saftey process that needs to be done -before- a new auto
system is implemented, like what the FDA does with drugs. But there
isn't. And to think that people would rather whine about a little
tobacco smoke.....

End rant.

So how much power is too much power? There's no definitive answer. I
have seen brake failure with as little as 60 watts on VHF-hi (a Ford).
Remembering that the auto makers are mostly responsible for any such
problems, you will just have to use your best judgment. Follow the
rules that say to use the least amount of power, and to use good
engineering practices.