... the band the cell phones are in (800-900 MHZ ...
That's true--as far as it goes. There is also GSM-1800, GSM-1900 and PCS, at 1.8GHz, 1.9GHz and 1.9GHz, respectively.
HONESTLY - if you stand near any sort of wire going up in the air (shroud, backstay for example) you ought to see some increase in received signal strength. This is because the RF way up above you is hitting that wire and can be conducted down.
"Can" being the operative word, here. We're talking near-microwave to microwave frequencies. They don't work like "garden variety" RF works. It can
happen, but the effect is completely arbitrary, because the behaviour of the "conductors" is completely arbitrary at those frequencies.
One other thing.
Don't pay any attention to things that say "Receives up to 20 miles" or some other such crap.
A signal can be received much further than that -
Depends. In free space there's the distance squared rule. But we're not in free space, we're in the atmosphere, which is full of water and dust and stuff. Again: We're talking near-microwave and microwave frequencies. The attenuation is much greater than at lower frequencies. And that's just line-of-sight: I.e.: Nothing in the way. At these frequencies, LOS is all
you have. Fixed-station microwave communications towers generally aren't placed more than 30 miles apart, and they're dealing with a good deal more power, and significantly better receivers than your average cell-to-handheld link. (Commonly, max. LOS for cellular and PCS is 10 miles, give or take, in open country or across the water.)
...the SENSITIVITY of the front end of the receiver is the issue!)
That's not quite accurate, either. It's the sensitivity and
the signal-to-noise ratio
. Which brings us to...
It turns out that for a variety of reasons, towers can pick up your tiny phone signals really well. Their huge antennas and expensive electronics can "hear" anything you send out.
Mostly it's the receivers in the towers. There's no end of things you can do to increase sensitivity, improve S/N and reject interference when you aren't space-constrained
(Ex-microwave communications systems and SatCom guy, in case you were wondering.)