Criminal’s using Jamming Devices

If I recall, it had 3 or 4 antennas on it, one for each band it's supposed to block. So it has a separate transmitter for each antenna. Big city police agencies use trunked 800 mHz systems, which would be a lot harder to block.

It's been a long time since I heard about trunk systems. Don't they continuously change frequency?  If so, that sounds impossible to jam.