I'm afraid you got it backwards, Dewey. The cops are on the 460 mhz side - the fire is on 800.
amickey, to hear the DC police, you will need to make sure that you set their freqs up as a UHF trunk, using 2 different offsets, as shown
here (just click on the blue text- it's a JPEG of ARC396 with the offsets and tables set up)
73s Mike