The fractional frequency stability of a 34-m-diameter beam-waveguide antenna

Advances in fiber-optic technology have made it possible to develop a new technique to isolate and measure the frequency stability of a large beam-waveguide (BWG) antenna. Through the use of the technique described in the paper, at both 46.5° and 37° elevation angles, under good weather conditions, the degradation of the the fractional frequency stability of signals passing through the antenna path was measured to be between 1.3 and 2.2×10^-15 for sampling intervals of 1024 s. These stability values apply to the portion of the antenna that includes the main reflector, subreflector, tripod legs, and six BWG mirrors. These test results are believed to be the first successful fractional frequency stability measurements made on the microwave optics portion of a large antenna to a level of 1 or 2 parts in 10¹⁵