The authors report the successful operation of an antipodal finline qu
asi-particle SIS mixer at 230GHz. The mixer is fed by a waveguide diag
onal horn and uses planar circuit technology and integrated tuning. Th
e mixer is testd over the frequency range 213-265 GHz and a receiver n
oise temperature of similar to 60K DSB over the whole of this range is
obtained. This work has shown that superconducting finline mixers hav
e low noise and are easy to manufacture, and are therefore suitable fo
r large-format imaging arrays.