Poor reception/decoding of Philly APCO 25 system

I am currently trying to monitor a couple talk-groups on the Philly trunked APCO 25 system. I have a BCD436HP and am using the RadioShack 800MHz antenna with SMA/BNC adapter. It seems like the beginning of every transmission is cut-off and transmissions randomly drop-out all the time (seemingly at the worst possible time...). The only way I can reliably follow a radio conversation is by holding the scanner up in the air and pointing it around like an idiot until I find the "sweet-spot" for the current transmission. Obviously this is not very practical and is very annoying. Is this antenna junk or what? I have tried the stock antenna and also another wide-band telescoping and they don't seen any better. When there are no transmissions the control-channel looks like it is reading full signal-strength so I'm not sure what else I can do. Are the police/fire/ems personnel dealing with these same issues daily??