An antenna capable of generating multiple beams that are close together and have side lobes of low level includes optics comprising a single main reflector and a set of primary sources, each source suitable for generating a beam taken up by the optics that transmits it, or suitable for receiving a beam picked up by the optics of the antenna. The setup and hold measuring circuit generates a reference signal and a data signal in response to an external clock signal in a test mode of operation. The filter conforms to the interior of a vessel wall when expanded and contracts to a consistent diameter without bunching when stowed. Tray tables optionally associated with the seats further omit any central slot and may define one or more pivot axes in locations different than exist in conventional seats.