On 16-Jun-2004, Elwood Dowd wrote:

That's the one, and there's the rub. Most (all?) of the carriers use
digital signals on 800MHz cells. Some (most?) can also use a newer
1.9GHz network. You have to know what kind of phone you have, and what
network it is using at a given time.

Some carriers (Verizon, Cingular, AT&T) operate networks on different bands
(both 800 MHz and 1`.9 GHz). Others (Sprint, T-Mobile) operate only at 1.9
GHz. Nextel currently operates exclusively on a different 800-900 MHz band,
but will likely be migrating to a new 2 GHz band.



My Verizon phone displayes "1X" when it is in a 1.9GHz network, and is
therefore legal to use in the aircraft. It says "D" when in a standard
digital network and "A" in an analog network, neither of which is legal.

Not Quite. Verizon uses CDMA technology. 1X is the latest version of CDMA
and is used on both 800 MHz and 1.9 GHz networks. Which band you are
operating on will generally depend upon your current location, and may be
difficult for an untrained user to determine. When your phone displays "D"
it means CDMA operation, including the pre-1X version.


The 1.9GHz cells don't tend to broadcast or receive at extreme
angles---they are often unusable in the air above about 3000AGL. Also,
at 140kt, it's pretty easy to go from one network to another quickly, so
I normally only attempt to use it below 3000 and either in populated
areas or along interstate highways.

The height limitation in urban areas is due to the fact that from a
significant altitude the handset will receive too many "pilot channels" and
will not be able to discriminate between them. This phenomenon of CDMA is
called "pilot pollution". The TDMA and GSM technologies used by some
carriers have different problems associated with operation at altitude.


Of course none of this counts the numerous times I have left the damn
thing on and discovered it at 10k feet. I have yet to be pulled over by
the cell phone cops, or hear of anyone who has, so I wouldn't be too
concerned in any case.


One thing that is important to remember is that, regardless of frequency
band or system technology, when you use a cellphone in an airplane you are
likely CAUSING massive interference to the network, possibly resulting in
many dropped calls, even if it works for you. That is why it is prohibited
by regulation. Unfortunately, such behavior is difficult to detect, and the
violators are rarely apprehended. So, if you like to think of yourself as a
courteous "good guy" (like most GA pilots) you will act accordingly.

--
-Elliott Drucker