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Technology Stocks : Qualcomm Incorporated (QCOM)
QCOM 170.90-1.3%Nov 7 9:30 AM EST
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To: Jon Koplik who wrote (104820)9/15/2001 1:14:10 PM
From: engineer  Read Replies (2) of 152472
 
I like these "experts". Because you can turn on your phone and use it from an airplane, then they must be able to be used all the time.

Extensive systems design went into how to layout a cellular network and the analog ones are the worst. They have a frequency reuse factor of 7, which means they rely on the fact tha the signal dops off across 7 cell sites to prevent jamming from another cell phone. In an airplane you ahve a much better line of sight path loss, so you can go across these cell sites and even if the switch could figure out which one to assign you to, you would still jam the ohter 2 sites that you can see.

As I stated, you could use it and for some limited time it works, but not on a regular basis. takes a whole other new system to do that.

And in the newere digital systems, they never deisgned the time tracking loops to go 450 miles an hour. They drop off at about 125 MPH for overall use, although a few instances have been reported of the phone working in faster airplanes. this was because on that particular fligiht, they happneed to be going the right way from teh cell to have the EFFECTIVE doppler speed apear like 125-140 mph.

It would be better to design a system which is for airplanes and assign a new freqneucy for it.
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