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Hmmmm, So, we should not use cell phones on mountain tops? Last time I was on Pikes Peak, I couldn't get one decent connection. Im not sure this is working out for me, logically. After a bunch of year in communications...and specifically communications security...introducing the new upper-end freq technologies, I surmise more bureaucratically centered issues here. See, at altitude, you MAY have access to distant cells beyond those in your immediate area. This makes you much more difficult to localize....until the law mandates GPS data transmission from every phone. Anyway, as I recall, the equation for line of sight horizon is 1.144 * sqr rt (height of eye in feet) = distance to the horizon in nautical miles. (This assumes the horizon is at sea-level...which, of course, it ain't, as a rule.) For radar freqs, substitute a multiplicand of 1.23. How do we get such different numbers? Grins, Dave Winters N2797H -----Original Message----- From: John Stevens [mailto:[EMAIL PROTECTED] Sent: Tuesday, March 07, 2006 2:54 PM To: [email protected] Subject: [COUPERS-FLYIN] AIRBORNE CELL PHONE USE ----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]---- One of the primary reasons that cellphones are prohibited in aircraft is that they (MAY) interfere with aircraft electronics. That is obvious. Just put a cellphone near a CRT computer monitor or near an unshielded set of computer speakers and you can either see or listen to the electromagnetic interference that they generate. Secondarily a cellphone will step up its' power relative to the signal that it is receiving so that these new phones can save as much battery power as possible - so inside a commercial airliner you are in the equivalent of a faraday cage with little openings to the "outside world". This will make a cellphone step up its power to try and poll a cellsite so that it can function. Now fill that faraday cage with lots of people with cellphones and all of the possible mixing of signals bouncing around inside. That's why they don't allow it. One person with a phone might be benign but add 20, 30, 40 or more people to that mix and you might have a serious problem if the right circumstances allow. Next, add "line of sight" to the equation - cellphones are designed to connect to the nearest "cell" that they can receive from ground level. This takes into account obstructions like buildings, cars, hills and other natural obstructions to your horizon. Get 4500-5500ft up in a coupe and you have nearly unobstructed views of potentially hundreds of cell towers and the voting system that the cell systems use can get a bit confused when you have simultaneous access to 20+ cell sites at the same time. At 5500ft your horizon (on a perfect day) is 97 miles away - using the general formula of (sqrt (altitude in feet / 0.5732))=number of miles line of sight to horizon Saying that - flying cross country in rural Georgia where the sites aren't too close together you probably aren't hurting anything, but anywhere within or near an urban centre you'll be causing some confusion for sure. The old "mobile" telephones use a fixed frequency channel to communicate with the public telephone network, the "airphones" use a combination of satellite and fixed ground stations to relay your call into the public network. They were designed from the get go to be in planes. Anyway - probably WAY over explained this one. But my $.02 and my one post a year.... John - EX CF-RGD - I MISS MY COUPE! ======================================================================== ===== To leave this forum go to: http://ercoupers.com/lists.htm ============================================================================== To leave this forum go to: http://ercoupers.com/lists.htm
