"Some Guy" wrote in message ...

You guys are acting as if the engines and flight control surfaces of
an aircraft are intimately tied to the plane's radio receiver, and the
slightest odd or out-of-place signal that it receives is enough to
send any plane into a tail spin.

Not at all; however, there IS obviously a connection between
various flight control functions (such as, say, the autopilot) and
the information given by the avionics (esp. "nav" radios using
ground-based sources such as VORs, etc.). It's not going to
"send any plane into a tail spin", but it can certainly cause some
problems.

All this while the air travel industry is considering allowing
passengers to use their own cell phones WHILE THE PLANES ARE IN FLIGHT
by adding cell-phone relay stations to the planes and allowing any
such calls to be completed via satellite. So I guess the feeble
radiation by my FM radio (powered by 2 AAA batteries) is enough to
cause a plane to dive into the ocean, but the guy next to me putting
out 3 watts of near-microwave energy is totally safe.

You DO realize that these are on very different frequencies, and
that the emissions of an FM superheterodyne radio are very
likely to fall right in the aviation band, don't you? Hint: if you have
to go look up "superheterodyne" to understand this question, I
have serious doubts regarding your qualifications to comment on it.

Getting back to the original question (poor to non-existant AM
reception), I understand the idea of aperature and long wavelenths of
AM radio and the size of airplane windows - but what about the effect
of ALL the windows on a plane? Don't they create a much larger
effective apperature when you consider all of them?

No. It's not the TOTAL area of the "apperatures" [sic] that
is important, it's the size of the individual openings. If this were
not so, then a conductive mesh could never be effective as a
shield.

And since the
plane isin't grounded, isin't the exterior shell of a plane
essentially transparent to all RF (ie it's just a re-radiator) because
it's not at ground potential?

No. "Ground potential" has absolutely nothing to do
with it. Hint: what do you think is the RF environment
within a perfectly conducting sealed enclosure, with
respect to outside sources, even if that enclosure is
completely isolated from any other surface or conductor?

Bob M. (KC0EW)

All this while the air travel industry is considering allowing
passengers to use their own cell phones WHILE THE PLANES ARE IN FLIGHT
by adding cell-phone relay stations to the planes and allowing any
such calls to be completed via satellite. So I guess the feeble
radiation by my FM radio (powered by 2 AAA batteries) is enough to
cause a plane to dive into the ocean, but the guy next to me putting
out 3 watts of near-microwave energy is totally safe.


I can't provide technical details of the operation because I don't know
them; but I am familiar with a number of totally RF screened environments
where use of electronic devices are tightly controlled. However, internal
relays are used to permit operation of cell phones - which I always
understood were specific models which had been certified for such use.

Dave

Dave Holford wrote:

All this while the air travel industry is considering allowing
passengers to use their own cell phones WHILE THE PLANES ARE
IN FLIGHT by adding cell-phone relay stations to the planes

I am familiar with a number of totally RF screened environments
where use of electronic devices are tightly controlled.
However, internal relays are used to permit operation of cell
phones

The point was not how the planes are being equipped to handle
in-flight cell-phone use.

The point was that consideration is being made to allow cell phones to
be used while the planes are in flight. That intentional radiating
PED's are even being considered for in-flight use when so much hype
and concern is being given to the weak radiation potential of some
non-intentional radiators like am/fm radios.

BTW, what is the potential of the local oscillators of small hand-held
LCD-screen TV's to overlap with aviation frequencies?

"Some Guy" wrote in message ...
The point was that consideration is being made to allow cell phones to
be used while the planes are in flight. That intentional radiating
PED's are even being considered for in-flight use when so much hype
and concern is being given to the weak radiation potential of some
non-intentional radiators like am/fm radios.

Because, as has already been pointed out, of the
differences in emission characteristics (and specifically
the frequency ranges likely to be affected) of the two
classes of devices.

BTW, what is the potential of the local oscillators of small hand-held
LCD-screen TV's to overlap with aviation frequencies?

I believe they should be somewhat less than is the case
with an FM receiver, but they're still a bad idea for
the same reason. Note that the analysis of the likely
frequencies provided so far has dealt solely with the
first-order effects of the receiver's local oscillator; we
have NOT discussed harmonics or other unwanted
emissions.

The problem is most obvious with FM receivers because
the standard 1st LO frequency is 10.7 MHz, and the
top of the FM broadcast band is adjacent to the bottom
of the aviation band (108 MHz) - which means that
simply adding the LO frequency to standard FM
broadcast frequencies can take you instantly into overlap
with the bottom 10.7 MHz of the aviation band (and
unfortunately, that's where a lot of the radionavigation
systems within that band tend to be). But this does
not mean that receivers for other services would not
cause similar problems. VHF television covers
frequencies below and above both FM and
aviation (two bands, 54-88 MHz for channels 2
through 6, and 174 to 216 MHz for channels 7
through 13). It is certainly very possible that receivers
intended for these bands would emit in the aviation
band. Other adjacent services that may be of concern
include public-service and commerical communication
bands (i.e., police scanners) and the 2-meter amateur
band.

Bob M.