[Boatanchors] Off Topic...?? possible RF interference with automotive electronics

[Sheldon Daitch]

Ian,

Many years ago, the US auto manufacturers would test drive new
vehicles at the VOA transmitter sites at Greenville and Bethany,
to see if there was an interference to the electronics on board
at that time.

I do not believe that testing is being done anymore and hasn't been
the norm for a number of years.  I don't recall any of the manufacturers
telling us there were RF problems, nor do I recall we ever had to
tow a vehicle out of the antenna field.

There was an incident where the engines on a blimp failed,
as the blimp passed by one of the Greenville HF sites:

*http://www.epa.gov/EPA-IMPACT/2006/February/Day-01/i895.htm*

We have a number of late model vehicles, mostly GM and Chrysler,
as new as 2009, which we routinely drive around the VOA facility
where currently I work and we've never had a failure we can relate to RF
fields. 

Remember, too, most FM and TV antenna systems are not at ground
level, with the exception of the few mountain top transmitter sites where
the antennas are mounted on relatively short towers.  I think it would be
quite difficult to have vehicle failure related to FM and TV transmissions
at roughly 99% of the FM and TV transmitter sites, since the antennas
may be as much as 1800 feet away from the vehicle.

Radar could be an entirely different category, as most ground based
radar systems aren't very high off the ground and some use very
high peak ERP. 

Speaking of RF interference, I knew of one small town radio station
which would, on occasion, pickup up interference in one of the
turntable preamps from a VOA transmitter at Bethany, but did not
have any apparent RF pickup from the 1 kW AM transmitter in
the same building, with the tower only about 50 feet from the
control room.  Go figure.

73
Sheldon
WA4MZZ








Ian wrote:
> Yes, this is off topic I guess but I can't think of a list that I subscribe
> to with a wider range of people with lots of hands on experience with RF.
> Perhaps somebody can suggest other lists that are more pertinent.
>
> I remember when I had an American Motors Rambler station wagon and my 25
> watt 2 meter rig would cause a significant drop in engine speed when I
> transmitter.  I think most of the problem was with RF causing interference
> with the cruise control.
>
> I remember though that some later car manuals cautioned against certain
> placement of transmitters in some areas of the cab to prevent interaction
> with the computer controlling engine functions.  One of which was on the
> passenger side of the firewall.
>
> With all the TOYOTA "drive by wire" systems... steering, fuel injection
> control replacing mechanical linkages, braking and the like reportedly
> experiencing problems which the manufacturer claims are NOT electronic and a
> few who have had problems report symptoms that might well be electronic to
> my way of thinking.  I wonder what those of us who "dabble" in electronics
> or work in it as a job think?
>
> I recall building instrumentation in the early 1960s using off the shelf
> logic boards using circuitry mixing discrete components that today would be
> a small part of a miniscule integrated circuit.   I was using selectable
> digital timing in the same custom designed metal desktop cabinet as fast
> rising 5KW pulse generators using high voltage switches and a coaxial charge
> line that produced the output of the system.   There were definite problems
> with those several nanosecond risetime electro magnet pulses causing
> problemns with the digital low voltage circuits.  I had to solve that
> problem with several late nights that also produced all too many "paper"
> cuts to my hands from the sheets of thin mu metal that I cut with scissors
> from rolls of mu metal to shield things and which I had to solder into boxes
> several places.  
>
> I keep expecting to see some mention of possible RF/electromagnetic
> interference with automotive electronics...
>
> I wonder if some of the strange behaviors reporting are from driving near
> some high power Radar, TV, FM, communications or even AM transmitters???
> (Maybe even from the "good buddy" in the 16 wheeler with a 3KW PILL
> amplifier on his CB generating a broad spectrum of interference as the
> automobile passed by the truck???)  That type of interference could explain
> the seeming inability of Toyota engineers to admit to being able to
> replicate the problems, assuming that we are being told the whole story.
> Some of those individuals anomalous operation of their automobile, seem to
> be credible individuals who did NOT accidentally step on the accelerator
> thinking it to be the brake or the gas pedal thinking it was the brake...
>
> Does anybody have any information about shielding and packaging and
> protection of those potentially troublesome computer packages in automotive
> products???  I'm wondering how many of them are protected from external high
> powered electromagnetic interference???
>
> Has anybody else been wondering about this or have any specific information
> about how well protected those systems are from external Electro Magnetic
> radiation?
>
> Maybe the highway patrol should vehicles should be outfitted with high power
> spark gap transmitters to disable cars during high speed chases??  :-(
>
> What are your thoughts?
>
> Ian, K6SDE
>
>
>