An isoflux aperture radiates into a wide, deliberately shaped pattern with significant off-boresight content. Enclosing that in a way that yields a stable coupling factor requires more volume than a flat patch fixture, which is why this hat is the largest in the S-band group by height. Coupling is specified 1 dB minimum, 3 dB typical and 6 dB maximum, measured against CSA-S-006-RH. As with every fixture in this range, the value of the figure is its repeatability: the same hat on the same antenna returns the same reading, which is what allows an acceptance measurement to be compared against a baseline. The RF shielded enclosure protects personnel during bench transmit and contains the test. It mounts to interface features already on the antenna without adding a bracket to the spacecraft and dismounts without tooling. The envelope is 97 x 97 x 104 mm (3.8 x 3.8 x 4.1 in) at 300 g with an SMA female interface, rated -70 to +100 °C. CSA-S-006-RH is the matching antenna.