The FM-10A-Loop is a heavy-duty, high performance FM loop antenna21.5" diameter FM loop. 360 degree reception - greatly improved reception versus internal or simple indoor dipole antennas. Heavy duty aluminum construction. Built-in balun - directly connect to your 75 ohm antenna line (your 75 ohm coax).Includes mast attachment hardware (no mast included, no coax included); easy to connect to use. Ideal for permanent installations at home (outdoors or attic installation) and office; also works fine on RVs and other semi-permanent installations.