Garmin Astro 320 Extended Range Antenna. The Extended Range Antenna 010-10856-30 from Garmin is compatible with the Garmin Astro 320 Dog Tracking GPS. Features of Garmin Astro 320 Extended Range Antenna: Compatible with Garmin Astro 320 Increases maximum range between Astro 320 and tracking collar by nearly 30 percent; up to 9 miles in flat unobstructed terrain Package Contents: Garmin Extended Range Antenna 010-10856-30