275 MHz of continuous coverage in one aperture makes this the workhorse of the S-band range. A spacecraft that would otherwise carry separate receive and transmit antennas carries this instead, saving two harness runs, two mounting interfaces and two acceptance test campaigns. The design is fully passive, with no LNA to bias, no current budget line and no active device requiring radiation qualification. Multipaction margin of 10 dB is verified at the full 20 W rating, which is the governing figure when one aperture both radiates and receives at S-band. VSWR is 2:1 through an SMA female interface, in a 97 x 97 x 18 mm (3.8 x 3.8 x 0.7 in) envelope at 190 g. Built for the harsh conditions of space operation across LEO, MEO and GEO, the sealed and vented housing addresses corona, multipaction, atomic oxygen and MMOD. Qualification is to NASA GEVS (GSFC-STD-7000) with random vibration to 14.1 GRMS, humidity per MIL-STD-810 Method 507.6 and a -70 to +100 °C operating and storage range. ATH-S-002-RH is the matching test hat. Certain small-volume orders can ship within days rather than the months typically quoted for space-qualified hardware.