Originally Posted by
flyinbob
I was talking to a guy a while back about the transmitter stuff and he said one concern about cell phone use is that because few cell phones work at 38,000 feet, or over vast expanses of the US while flying, some "experts" have tried to bump up the power, or range, or their cells, and that is what could cause problems and interference. Don't know if it is true but with some people so addicted to their electronics I can see it being an issue.
Partially true I'd guess, but not from people actually modifying their cell phones. If anything, fewer and fewer people nowadays know a darn thing about how their electronics work. You don't have nearly as many amateur radio operators or other electronics hobbyists as in the days of yore.
What actually can happen, with both GSM (most of the world plus Cingular and T-Mobile USA), and CDMA (Verizon, Sprint, and some of Asia) technology is that the phone's transmit output is variable power. If it can't find a cell to connect to, it can raise its transmitter power to try harder. If it does find a cell but its signal into the cell is weak, the cell can command the handset to raise its transmit power.
The older analog and TDMA 1st-gen digital phones were dumber. They had a fixed transmit power (300 milliwatts if I recall). CDMA handsets I believe have a 300mw maximum but initially start out lower. GSM handsets I believe can transmit up to 1 watt power. (I'm talking about handsets, not carphones or bagphones where I think 3 Watts is still allowed).
A planefull of left-on mobiles all pumping out maximum transmit power trying to connect to a ground station would be putting out a lot more total RF than the same number of phones in a ground-based metal can like the same plane on the tarmac, or the same people and phones in a bus or a railcar.
I believe (sorry, don't have the cite) that some of the in-air mobile systems will be using a minicell in the plane itself, explicitly programmed to command the phones to use minimum power output.