I get that our phones can pick up signals from towers since they have a much stronger signal and enough power for that. But what doesn’t make much sense to me is how our phones’ tiny antennas can still produce a signal strong enough to reach the tower as well and create a two-way connection. How is that possible? Does the tower just pick up weak signals and strongly amplify them?
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Your typical cell phone transmits at either 0.6W or 3W. This is good for somewhere between 22 and 45 miles with no obstructions. Most cell zones have a radius (they’re not necessarily circular) of around 1.25 miles. So in urban environments where you are more likely to find obstructions you’re well within your phones range. Cell towers are on towers (ok it’s in the name) and/or at high elevations to reduce the number of obstructions and maximize the range.
Radio receivers work on VERY low power levels, but have great sensitivity. Your phone will be able to work with a received signal strength of around -120 dBm which is the equivalent of 1 femtowatt (1 x 10^-15 watts).
The GPS satellites transmit at “only” 25.4W and are 12550 miles away (if directly overhead which they usually are not).
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