Joseph wrote:

On Mon, 11 Oct 2004 11:38:10 -0700, DaveC wrote:

Cell phone usage is restricted on all domestic commercial flights by the FAA,
so the flight attendant keeps telling me.

I seem to recall that this wasn't so, early in cellular history. Weren't we
able to use cell phones on flights, long ago?

Is cell phone usage also restricted on private jets, etc. for similar
reasons?

Restriction of cell phones from planes is not due to the interference
to avionics, but is more of concern that it will interfere with
land-based communications. When you're up at a height and you attempt
to use your phone you are hitting a whole lot of cell sites as once
and if lots of people did this it would make a real mess of land-based
cellular service. So it's more of an FCC mandate than it is of the
FAA.

I thought that the base station antenna patterns pretty much ignore any signal
greater than a few ( maybe ~10 ) degrees above the horizon.


Graham

Brian Case wrote:

Actually it could work very well, and I have seen this proposal from
several different sources. The Idea is to install a low power cell
phone tower into the airliner.

Well, it would work well, but not if they actually used the cellular frequencies
(AMPS). If they installed a PCS processor in the plane, modern PCS phones would
communicate with it and not fall back on the AMPS frequencies.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

Pooh Bear wrote:

The origin of the ban was due to concerns about cellphone transmissions
interfering with onboard avionics.

The origin of the ban on cellphone usage at altitude was to prevent phones from
hitting multiple receivers which were using the same frequency. The designers of the
AMPS system counted on being able to have many "cells" use the same frequency set
because they were far apart. Put the phone in the air, and several of these stations
would receive the transmissions from the call.

The origin of the FAA ban on electronic devices is as you say, but it is not unique
to cell phones.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

"Pooh Bear" wrote in message
...
DaveC wrote:

Cell phone usage is restricted on all domestic commercial flights by the
FAA,
so the flight attendant keeps telling me.

I seem to recall that this wasn't so, early in cellular history. Weren't
we
able to use cell phones on flights, long ago?

Is cell phone usage also restricted on private jets, etc. for similar
reasons?

So my question... what is the technical reason for restriction of cell
phone
us on commercial flights? Is this reason valid, technically? Or is it
simply
an excuse to force anyone who needs to make a call to use the airline's
on-board phones (and pay their outrageous rates)?

The origin of the ban was due to concerns about cellphone transmissions
interfering with onboard avionics. This is more likely to be a concern
with older
a/c. There is no hard data that I know of that substantiates the concern.
There
is some anecdotal evidence of interference though.

Everyone's got a conspiracy theory. Here's another: The ban on cellular
phones is kept alive by the book publishing industry. Some in the evil cabal
may actually have the best intentions: Trying to get cell phone addicts to
shut the phuque up and try reading something for a change.

Pooh Bear wrote:

The origin of the ban was due to concerns about cellphone transmissions
interfering with onboard avionics. This is more likely to be a concern with older
a/c. There is no hard data that I know of that substantiates the concern. There
is some anecdotal evidence of interference though.

Sorry, there are two issues. The FAA has it's own concerns about ANY
electronic devices. There's not hard and fast info on a lot of these
devices and the FAA has gotten more restrictive over time. However, the
AMPS regs specifically prohibit it without specifying the reason. It would
seem unlikely that a prohibition against airborn use however has anything
to do with air navigation because NOTHING ELSE the FCC regulates really
addresses that issue.


As another poster has mentioned, cellphones don't work well at altitude.

Wrong. AMPS / Analog cell phones, the ones the regulatory applies to, work
just fine from altitude. Actually too well. That was demonstrated on 9/11.
However some of the digital (PCS, for example) services, don't work at all
airborne (but they are not prohibited by regulation either).

G.R. Patterson III wrote:

Brian Case wrote:

Actually it could work very well, and I have seen this proposal from
several different sources. The Idea is to install a low power cell
phone tower into the airliner.


Well, it would work well, but not if they actually used the cellular frequencies
(AMPS). If they installed a PCS processor in the plane, modern PCS phones would
communicate with it and not fall back on the AMPS frequencies.

It would be a real can of worms. If everybody had a GSM phone in the
US it might be doable. But every carrier these days tends to market
a multimode phone that bounces between CDMA, old style TDMA, analog AMPS,
GSM, and a couple of proprietary schemes like iDEN.

It's going to have to be a "only [insert carrier here]" phones work onboard
United's flights.

On Wed, 13 Oct 2004 12:16:13 -0400, Ron Natalie
wrote:

G.R. Patterson III wrote:

Brian Case wrote:

Actually it could work very well, and I have seen this proposal from
several different sources. The Idea is to install a low power cell
phone tower into the airliner.


Well, it would work well, but not if they actually used the cellular frequencies
(AMPS). If they installed a PCS processor in the plane, modern PCS phones would
communicate with it and not fall back on the AMPS frequencies.

It would be a real can of worms. If everybody had a GSM phone in the
US it might be doable. But every carrier these days tends to market
a multimode phone that bounces between CDMA, old style TDMA, analog AMPS,
GSM, and a couple of proprietary schemes like iDEN.

Given that it's no big deal these days to make a multi-mode,
multi-band phone, why do you think it'd be so tough to make a
multi-mode, multi-band base station in the A/C? Certainly would be
easier if all phones were CDMA, of course. ;-)

Klein

On Wed, 13 Oct 2004 12:13:36 -0400, Ron Natalie
wrote:

Pooh Bear wrote:

The origin of the ban was due to concerns about cellphone transmissions
interfering with onboard avionics. This is more likely to be a concern with older
a/c. There is no hard data that I know of that substantiates the concern. There
is some anecdotal evidence of interference though.

Sorry, there are two issues. The FAA has it's own concerns about ANY
electronic devices. There's not hard and fast info on a lot of these
devices and the FAA has gotten more restrictive over time. However, the
AMPS regs specifically prohibit it without specifying the reason. It would
seem unlikely that a prohibition against airborn use however has anything
to do with air navigation because NOTHING ELSE the FCC regulates really
addresses that issue.


As another poster has mentioned, cellphones don't work well at altitude.

Wrong. AMPS / Analog cell phones, the ones the regulatory applies to, work
just fine from altitude. Actually too well. That was demonstrated on 9/11.
However some of the digital (PCS, for example) services, don't work at all
airborne (but they are not prohibited by regulation either).

Actually, PCS and 800 MHz digital CDMA work just fine airborne
provided there are only a few CDMA base stations near the aircraft,
but flying over a city it is hopeless. The problem is that in CDMA
systems many base stations transmit on the same wideband channel,
interfering with each other. The phone will never attempt to transmit
because it never succeeds in acquiring the system.

Klein

Klein wrote:

Given that it's no big deal these days to make a multi-mode,
multi-band phone, why do you think it'd be so tough to make a
multi-mode, multi-band base station in the A/C? Certainly would be
easier if all phones were CDMA, of course. ;-)

That would be fine if there were some industry cooperation with the
people planning on offering the airborne service. But the plethora
of incompatible modulation schemes now sort of demonstrates that this
level of cooperation isn't likely .