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