I'm listening to Alton PD right now on the primary 155.190. They usually have more traffic then east Alton, but it's still not as busy as say...St.Louis. Can you pick up Woodriver PD, 155.115?
Is your scanner a base or hand held? Try making sure the antenna is on good and snug (Don't over tighten!) if it's a base, and try moving the scanner to a different part of your house. The signal could be blocked, which could be why you are not hearing anything.
-RC-