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Re: Don't trust the net too much
On Wed, 12 Jul 1995, Doug Hughes wrote:
> This just goes to show that we live in a world of electromagnetic soup.
> We really don't know how it effects the body long term, or whether, having
> more mission or life critical electronics could be interacting with over
> devices. This was the theme of the program.
There have been many examples of this - several cases of hams having
their pacemakers go nuts when they keyed their transmitters, etc. But
that doesn't mean that aviation avionics are sensitive - in fact, devices
that are specifically designed to receive RF of a specific frequency are
usually designed to reject RF of a different frequency, especially type
accepted radios (the avionics package is required to be type accepted for
that particular class of service, which includes spurious rejection,
intermod products down XX dB, etc.)
> Another example was on an airplane (several of them.. older ones mostly
> I believe) pilots would occassionally lose instruments (VLS, etc) when
> passengers would activate portable transistor radios and such. Particularly
> radios.. But there was another case involving a portable computer.. These
> cases have been documented. It's a good thing the plain wasn't on a
> landing approach during a storm, or things could've gone very bad very
> quickly.
A transistor radio puts out such a minute amount of RF (at 455 KHz and/or
10.7 MHz, the IF freqs of the radio) that most insturments designed to
pick up RF can't detect this stuff from more than a few feet away. FCC
regulations say that if your avionics is being interfered with, it's YOUR
problem, not the guy that just turned on his radio. If someone's avionics
is being interfered when I turn on an AM/FM transistor radio, then I'd say
that he either needs to get his avionics fixed, or he's using illegal
consumer-grade radios (which are usually junk anyway - even much ham radio
gear is garbage, unfortunately), instead of the type-accepted stuff he's
supposed to be using. I'd be interested in finding out more about this
guy and his "VLS-jumped-when-someone-turned-on-their-radio" story.
> I heard about the portable computer via a different source. The guy
> kept turning his computer on. The instruments would do a little dance.
> The captain would tell the stewardess, she would tell the passenger, he
> would turn it off for a while. Then, he would turn it on and repeat..
> Until finally he refused to turn it off, so they confiscated it and
> returned it at the end of the trip. Urban Legend? maybe..
The early laptop computers would put out an amazing amount of crap. I
used to have a Zenith laptop, and when I'd turn the thing on, it'd throw
out junk that I could hear on every radio in the house, including the 2m
FM stuff, the HF rig, and I could even hear it out in my car on the 2m
mobile! I can believe it, but that's no excuse for just saying, "well,
let's just ban all of it..."
> Believe what you want, but investigate the reports before dissmissing it
> out of hand as propaganda. I'd rather stay alive than rely on "theoretically
> it shouldn't matter." :)
My point is, it's not your, nor my responsibility to refrain from using
our radios - it's the responsibility of the avionics people to make sure
that their radios are within spec and are kept that way. If they don't
bother, that's not my fault.
> Keep in mind that newer planes (767, 757) let you do anything you want
> while the plane is in flight (but now while landing or takeoff), so they
> probably build better instrumentation and cabin shielding into the planes
> these days. If they say keep it off, chances are they have a good reason..
Again, my contention is that they don't.
> If you find categorical evidence to the contrary, I'm sure I would be very
> relieved to see it posted here. (rather than wondering if somebody
> in one of the 30 rows ahead of me might decide he knows better)
The ng rec.radio.amateur.misc might have some additional stuff in the FAQ,
and the ARRL certainly has a mountain of information on this - I'll poke
around. 'echo help|Mail [email protected]' might yield some interesting
things...
--
Ed Carp, N7EKG [email protected], [email protected]
801/534-8857 voicemail 801/460-1883 digital pager
Finger [email protected] for PGP 2.5 public key [email protected]
Q. What's the trouble with writing an MS-DOS program to emulate Clinton?
A. Figuring out what to do with the other 639K of memory.