It depends upon whether you want to hook something directly to the phone (such as an external amplified omnidirectional antenna) with the appropriate connector, or if you want to do this wirelessly. It also depende on you are looking at a fixed location, or a mobile one...
If you have LOS to the nearest cell tower, you can use a simple UHF yagi directional antenna pointed in that direction.
Alternatively, there are devices that act as amplified antennas, that rebroadcast the amplified CDMA signal wirelessly inside a structure. They operate similar to a "repeater".
Improve CDMA range
Re: Improve CDMA range
