Ok I suggest a AntennaCraft U8000 UHF antenna aimed at about 102 true - 109 degree magnetic compass and a AntennaCraft CS600 VHF antenna aimed at about 325 true - 332 degree magnetic compass. The 2 antennas are connected together with a UVSJ = UHF / VHF , separator joiner ,
http://www.solidsignal.com/pview.asp?p=UVSJ . The UHF antenna is connected to the UHF port of the UVSJ and the VHF antenna is connected to the VHF port of the UVSJ. The antenna amplifier that you have is connected to the port on the UVSJ that says LINE. The radio shack antenna amplifier that you have (like most all of radio shack branded products) is not the best of quality and design. How ever give it a try. Here are places to by antennas and etc. ,
http://www.solidsignal.com ,
http://www.starkelectronic.com ,
http://www.amazon.com ,
http://www.3starinc.com