The celluar phone network is a complicated engineering challenge, and thus the equipment is designed to make assumptions on things to ensure efficiency of the network. The signals from cell phones are within the 800Mhz and 900Mhz ranges for the old analog types. The new PCS ones are in the 1.3Mhz range (I believe, they're over 1Ghz anyway). These signals are nearly exclusively line of sight. There is no bending, and in fact, these signals can be stopped by pine needles.

Boosting signals from a cell phone should be used with care, because of the nature of a cellular network. Cellular phone output wattage is limited so that the phone will only work so far from the tower. This is necessary with the design of a "cellular" network. The other factor is how 911 calls are handled. With most newer handsets, there is an entry programmed into your phone called "Emergency Number". When this number is dialed, the phone will handle this number differently. Instead of trying to work through your paid carrier, the phone may, connect you to the closest cellular tower, regardless of provider. Now you're probably thinking, but if I'm moving, how is the call transferred between competing carrier cell towers? Beats me, but 911 calls are supposed to be handled differently than all other calls, without regard to carrier, or subscriber status. This is why phones with no service can still dial 911. If you let your children play with powered non-subscribed cell phones, they could still initiate a call to 911.

So, getting to the point of the boosting option, that should definately only be used when you are NOT in a dense cellular network. Boosting your signal and dialing 911 may cause problems. Usually, if you are within the same network (say, Cingular), then the system will determine the best tower to receive your call from, and "ignore" any other "hits" your amplified cell phone makes with it's towers. If you have the amplifier and hit multiple towers on multiple providers, I don't believe there is any protocol on how to handle this case. There probably is, but I don't know about.

Like you said, the height of the antenna and line-of-sight to the receiver will make all the difference.

Another thing with cell phones, in the U.S. there is a move to "Phase II" cell phone 911 service. This service uses either the phone, towers, or a combination of both, to determine the locatio n of your cell phone. These will be displayed on a map in the 911 call center to show your location. Some areas don't have Phase II, and you should always give your cellular phone number and location you are calling from, as a cellular 911 call may not always be routed to the jurisdiction you are in.

I should also note that for the privacy concerned, a recent case of a bouncer murdering a young woman in NY pointed out that your cell phone "ping" signals are recorded AND STORED by cell phone carriers. A ping signal is a signal that lets the network know which tower the phone is closest too, so that calls to it can be routed quickly. It is possible that these signals are recorded from ALL towers your phone "pings" and thus, your location triangulated. I'm not a lawyer, but what scares me is that they could be used in civil cases, and not just criminal cases. If you're somewhere you don't want to be, then, perhaps you want to turn off your phone. <img src="/images/graemlins/smile.gif" alt="" />

That's all I know. And I'm not the expert.