Coaxial feed for multiband antenna

A multiband antenna system comprising:

• a primary reflector;
• a subreflector affixed relative to the primary reflector;
• a coaxial feed extending from the primary reflector toward the subreflector, the coaxial feed comprising:
• a tubular high-band (HB) waveguide, the HB waveguide including an outer conducting surface, an inner HB conducting surface, and a HB aperture defined by the inner HB conducting surface;
• a tubular low-band (LB) waveguide disposed coaxially around the HB waveguide, the LB waveguide including an outer feed surface, an inner LB conducting surface, and an annular LB aperture defined by the inner LB conducing surface and the outer conducting surface of the HB waveguide;
• and
• an annular high-band (HB) choke located in the outer conducting surface of the HB waveguide, the HB choke being axially offset from the HB aperture;
• a tracking pedestal supporting the primary reflector, the subreflector, and coaxial feed, the tracking pedestal configured for tracking communications satellites;
• a HB diplexer positioned behind the primary reflector and operatively connected to a HB throat of the HB waveguide;
• a LB turnstile junction positioned behind the HB diplexer and operatively connected to a LB throat of the LB waveguide;
• and
• a LB orthomode transducer and diplexer positioned behind and operatively connected to the LB turnstile junction.