What type of antenna is best to receive KNAUs signal?
You can never have enough antennas! A roof-mount is very good, assuming it is pointed in the proper direction. Roof-mount antennas will also help you pull in distant TV signals (until everything goes digital that is). KNAU uses some very expensive ($500) products from a broadcast company called Scala. Less expensive brands include Weingard, Channel-Master, and others. There are many choices. Expect to pay $50 to $100 plus mounting hardware.