Important factor in 800Mhz reception is to use low loss coax especially for longer runs. I found that this dramatically increases the number of transmissions I hear on My Pro-96. One thing to consider is to have your antenna coax wired with the same end as the scanner connector (BNC type for the Pro-96) This will also help the reception as every time you have an adapter to go from one type of end to another (UHF to BNC for example) you also have a loss in signal.
Rob