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

Dave Baxter dave at emv.co.uk
Wed Feb 1 09:39:21 UTC 2006


That's a US MIL standard, not a civilian spec.

Also, Some of the 600V/m tests in the low microwave region (L & S band)
are not done yet, as most test houses (and manufacturers own facilities)
do not yet have the extremely expensive equipment needed.  Those quoted
spec's are old versions too afik.

It's not just upgrading the RF generation systems (sig gens, amplifiers,
antenna's etc) that is needed, that's just throwing money at it, and
making rack space.  Most of the automotive anechoic/semi anechoic rooms
will just not work at those frequencies, without extensive (and
expensive) re-lining or other absorber augmentation/replacement.  Not to
mention the field sensors.

Other people in our industry have said that Ford and GM almost seem to
be trying to out test each other, the way the proposed test spec's keep
changing.

About the only exceptions are military facilities, they cost an order of
magnitude to build and are not available to civy street on a day to day
basis in any case.  Even if they'd let them on site...

As to the time averaging effects for human safety.  Most of that is
based on the assumption that the effects are thermally based.
Electrical equipment of course, can be upset by a single "Peak" event,
so the test spec's are (may be) right in that respect?

I won't get on one of my other pet hates with modern equipemnt, the lack
of "watchdog" timers and auto recovery schemes.  Not rocket science,
but...

I think we're off topic here.  If you find you need to run multi kW
power levels for an APRS tracker, you may be doing something wrong!
Regardless of any EMC implications...

Cheers.

	Dave G0WBX.


> -----Original Message-----
> From: kc9umr at freqradio.com [mailto:kc9umr at freqradio.com] 
> Sent: Tuesday, January 31, 2006 2:56 PM
> To: TAPR APRS Mailing List
> Subject: Re: EMC (was RE: [aprssig] APRS in a Car)
> 
> Radiated Susceptibility for MIL-STD-461E is generally tested 
> to 200 V/m.
> 




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