RE: [Leica] Re: New Aviation Rules

["Austin Franklin" <darkroom@ix.netcom.com>]

> Trust me, a cell phone on a
> plane could conceivably trigger every cell tower within several tens of
> miles.

When the cell phone is inside a completely enclosed metallic structure?  I
can't get service in Home Depot!

Any way, causing the CELL service any problems was NOT the issue, it was
causing the avionics a problem, was the issue.

> One other point--if a cell phone shouldn't work from a plane, how do we
> explain the numerous cell phone conversations from the doomed
> airliners on
> Sept. 11?  I don't think all of them were using the plane's own
> radiophones, and several of the people who talked to the survivors said
> that so-and-so called on "his" or "her" cell phone.

They weren't cell phones from what I understand, but the on-board plane
phones...  Do you know they were in fact cell phones?  I don't know that the
people who received the calls actually knew, or even really asked, if the
people on the other end were on their cell phones?  If you really know they
were on cell phones, and you have a source for this, I'd like to check it
out.

> As far as interference goes, the issues become very complex.  In the
> presence of any two imperfectly connected conductors, which act as a
> rectifier, any radio signal can mix with any other radio signal to create
> sum and difference frequencies, or radiate multiples (harmonics) of the
> initial frequency.  Cell phones don't operate on the same frequencies as
> navigation equipment.  But mixing effects within equipment or nearby
> objects can create other signals which could conceivably interfere with
> navigation.  On a plane, where one "oops" can get you killed,
> it's probably
> best to avoid random and uncontrolled radio signals as much as possible.

I believe that's really not correct.  If that were the case, other
electronics would have the same problem with cell phones, and they just
don't.  The avionics would be designed such that it is not susceptible to
other electronics...the fact that the airplane has a LOT of other
electronics on board should attest to that...

> As for computers, CD players, etc:  Any digital device has clocks which
> create square waves--waves that are turning on and off instantaneously
> rather than oscillating smoothly.  Square waves are by their
> nature loaded
> with harmonics.

> And there are many such square waves in digital devices,
> because clock frequencies are routinely multiplied and divided to get
> various timing pulses.

It's the energy of the harmonics that matters, and the energy is very low.

> Shielding and bypassing can eliminate the radiation of such radio "hash"
> for all practical purposes.  But given the marketplace, devices that have
> been made cheaper by not including such refinements are going to be
> around.  For a real eye-opener, try putting a portable shortwave
> radio next
> to your computer and tune around.

What frequencies are you talking about?  I have a SW radio right next to my
computer, two scanners, two printers etc.  I don't get any interference.
Yes, you can get SOME interference with some devices, but it is VERY
localized (ie, very close proximity).

I believe you are exaggerating the magnitude of the issue substantially.
This is VERY low energy we are talking about here, and as such, I do not
believe it is possible for it to cause the problems you so envision.

> Laptops are more tightly controlled and tested than the cheap consumer CD
> player you picked up at K-Mart for $19.95, which is why the former may be
> allowed and the latter not.

WRONG.  Notebooks and ANY consumer electronics are subject to the same
regulatory requirements, it has nothing to do with cost.

> Finally, U.S. FCC Amateur regulations state that no amateur radio
> transmitter may be operated on board a ship or plane without the
> permission
> of the captain or master.  I believe there are similar
> restrictions in most
> other radio services.  So whether there's a good reason or not, the pilot
> has discretion, and he's bound by the policies of his company.  As stated
> above, there are good reasons.

Do you KNOW there is a law that prohibits the use of (specifically) cell
phones on airplanes?  I go on a ferry boat a lot, and there is no such
restriction for cell phones.  I can only guess that this restriction you
believe does not pertain to cell phones, but if you have a URL for an exact
wording of this "restriction", I'd be interested.

Irrespective of this, the claim was made that it interferes with the
avionics.  From doing FCC/EMI work for over 20 years as well designing MANY
pieces of digital equipment, a lot of what you say above has absolutely NOT
been my experience at all, and goes against practical engineering.  I do
agree with your comments about wireless distances though...but I am
skeptical about how effective that is inside a completely enclosed metallic
structure.

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