Here's one way to keep a decent signal on your cell phone...
9DB 30 inch Super Trucker Antenna - Omni Directional
The best Trucker antenna available period from any manufacturer!. Covers all North American Carriers on 800 MHz and 1900 MHz including CDMA , TDMA , GSM , EVDO , HSDPA ,EDGE, iDEN and ANALOG , This bad boy will leave all the other drivers drooling and begging you to know where you got it!!