EMI (was: Re: Don't trust the net too much)

[paul@poboy.b17c.ingr.com (Paul Robichaux)]

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Ed Carp said:

> This sounds like absolute propoganda.  If you do the calculations, you'll 
> see that a 1 watt transmitter sitting 100 feet away from your target will 
> generate an EMF less than that 1000kW ERP TV transmitter array you just 
> flew over.  If aircraft avionics were *that* sensitive, we'd have planes 
> falling out of the sky, and we don't. 

Oh, yes-- we do. The Army lost a small number (two or three) of of
UH-60 Black Hawks in crashes where the flight control system suddenly
commanded extreme pitch or attitude changes. Why? In all the crash
cases, EMI from nearby TV or FM transmitters was found to be the
proximate cause. The Army, and Sikorsky, immediately went to work to
better shield the FCS from EMI.

It's interesting to note that the Navy's SH-60, a UH-60 variant, was
designed from the start to be EMI-immune. Ships' radars operate in the
10-100kW range, and that's a lot of EMI when you're landing 15-20m
away from the radar mast.

- -Paul

- -- 
Paul Robichaux, KD4JZG       | Do you support free speech even when you don't
perobich@ingr.com            | like what's being said?
		 Be a cryptography user. Ask me how.


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