Chris W wrote:
There is a some kind of handshake routine
that is timed and if it takes your phone more than the alloted time to
respond, it wont work even if there is plenty of signal strength. Sorry
I don't remember for sure which digital service this is, but I think it
is GSM.

It's not CDMA as I get 20-25 miles with my external nondirectional mag
mount antenna on my truck.