What type of setup? Mobile or Base? How many miles is the repeaters? What type of scanning are you doing? I have 3 Antennas and all work nice. Check out youtube too. Have fun, I just got the Uniden BCD996P2 too this week, wow awesome scanner!
any antenna thats outside, as most of what you have is analog. If you have an old tv antenna, point towards alton , you should be able to pick up ISPERN AND ALTON