EMC (was RE: [aprssig] APRS in a Car)

kc9umr at freqradio.com kc9umr at freqradio.com
Tue Jan 31 09:55:57 EST 2006

Radiated Susceptibility for MIL-STD-461E is generally tested to 200 V/m.

> All cars (and just about all electrical/electronic products) now have to
> pass stringent EMC tests before being allowed to market.  The Civy
> levels for transport systems (cars and the like) is I think some 50V/m,
> HF to VHF. Military tests are even higher...  MUCH higher!
> For domestic stuff, 3V/m, Industrial, 10V/m.  Not that it helps much in
> truth....
> Emissions are usually a problem these days for the likes of us.  The
> limits are to protect broadcast services, where signal levels are
> usually in the range of several mV's, not the single figure uV's that we
> often look for.
> Many common rail diesel engines now emit more QRM than the spark
> ignition system petrol(gas) engines they replace.  (The inverters that
> generate the high voltage for the injector solenoids are often a source
> I believe)  But, that level is still below the EN limits, even though
> for us it's the equivalent of an S9+ signal, and usually broad band in
> nature, so almost impossible to blank out.   Don't go messing with the
> injectors, you'll mess up the engine's fuelling map if you add diodes
> for example, and also run the serious risk of engine damage.
> Susceptibility, is not usually a problem, you'd have to run silly power
> levels (kW's) and have a very badly installed radio/antenna to cause any
> real problems for the vehicle, but, you should still take care, and only
> run the minimum power needed to keep the QSO/link running.
> Many of the automotive test houses (EMC facilities) have CB, HAM and
> Military radios and antenna's available to them, just to make sure.  But
> those particular tests are not a requirement for the standards, just
> that some manufacturers like to have them done.
> If your car/truck/van/bike(?) starts to misbehave (misfire, odd
> lights/warning, wipers starting/stopping etc) when you TX, stop TX'ing,
> or at least reduce the RF levels, till you find out what and why.
> Any accident so caused, and investigated etc, you could find yourself
> with no insurance as a result, and maybe even no drivers licence after
> the court case!
> Take care, great care!..
> Dave G0WBX.
> (Take a look at our company web site, I may know more about this than I
> care to admit!  www.emv.co.uk)
>> -----Original Message-----
>> From: Dale Blanchard [mailto:wa7ixk at earthlink.net]
>> Sent: Monday, January 30, 2006 1:26 AM
>> To: AA3JY at Winlink.org; TAPR APRS Mailing List
>> Subject: Re: [aprssig] APRS in a Car
>> AA3JY at Winlink.org wrote:
>> > Dave wrote:
>> >
>> > A lot of modern cars do not have "Always on" power ports
>> any more.  It
>> > seems to depend on the philosophy of the individual maker.
>> The Honda
>> > Accord I have now does not.  Other cars I've had in the
>> last 5 years
>> > have..
>> > ===============> > You think that is bad...
>> > BMW's single-wire, CAN-bus electrical system, which greatly
>> reduces the number of wires used in the main harness and
>> dramatically reduces weight and complexity.  Part of the
>> CAN-bus is a new fully electronic instrument cluster
>> featuring Info-Flatscreen for additional system information
>> available at a glance.
>> >
>> > One would wonder if RF will have any affect on this new system...
>> >
>> > Regards,
>> >
>> > Clay AA3JY
>> > (via WL2K)
>> >__________________________
>> I have heard that BMW has tested some cars in a high RF
>> facility similar to what the military does.
>> I have great faith in the CAN systen. But can not afford one.
>> It has been used for over 10 years now. Some one should have
>> heard some rumers by now.
>> It is not a new system.
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