Absolute calibration of a wideband antenna and spectrometer for accurate sky noise temperature measurements


Corresponding author: A. E. E. Rogers, Haystack Observatory, Massachusetts Institute of Technology, Westford, MA 01886, USA. (arogers@haystack.mit.edu)


[1] A new method of absolute calibration of sky noise temperature using a three-position switched spectrometer, measurements of antenna and low noise amplifier impedance with a vector network analyzer, and ancillary measurements of the amplifier noise waves is described and compared with other methods of calibration. An initial test of the method has been made using brief observations from 55 to 110 MHz at West Forks, Maine, to estimate the sky noise spectral index. Estimates are made of the accuracy that might ultimately be achieved with observations to detect or set limits on the red-shifted 21 cm line at a radio quiet site. It is concluded that an antenna reflection coefficient better than about −20 dB is required to avoid being limited by the accuracy of the antenna reflection coefficient measurements using a vector network analyzer.