This is the passive configuration of the dual-port S-band omni, for architectures where the receive chain already carries its own LNA or where the mission prefers all active devices inside the bus. Transmit and receive share the aperture but present as two independent SMA female interfaces, so the radio can be wired without a diplexer. Axial ratio is 3 to 4 dB on transmit and 1 to 2 dB on receive, and VSWR holds at 2:1 across both bands. The envelope matches the wideband single-port antenna at 97 x 97 x 18 mm (3.8 x 3.8 x 0.7 in), at 200 g. Designed for the harsh conditions of space, the sealed and vented housing addresses corona, multipaction, atomic oxygen and MMOD. Qualification follows 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-003-RH is the matching test hat and exercises both ports, allowing port isolation to be verified on the bench before the spacecraft is closed out.