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Old 5th Aug 2012, 18:20
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Keef

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There are some technical effects, too. I'm sure Googoo will reveal much more than I know.

In the UK, cellphone aerials are set to work horizontally and below. If there's reflection from something on the ground, then the signal may go up as well. The problem when the aerials worked with aircraft at altitude was that the airborne phone would access multiple towers and confuse the system. Some countries have a setup whereby a small number of towers have an upward-pointing aerial for aircraft - I think the USA is one such.

Straight GSM works on time-division multiplex, which sets an effective distance limit of about 20km, after which your returning signal is outside your timeslot. Although you may have a signal indication, you can't actually use it. Some rural sites have longer time slots, which increase the maximum range.
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