The Cornell Radio Polarimeter

Abstract

The Cornell polarimeter operates on 201.5 mc with a bandwidth of about 10 kc. This bandwidth is an order of magnitude smaller than previously used. The instrument is basically similar to the interference polarimeter built by Little and Payne-Scott, although it does not operate on an interference basis. The two circular components and the phase and correlation are measured. Ratios of the measured quantities are used graphically to find the polarization percentage and axial ratio. The system is calibrated on a relative basis by transmitting noise from a distant vertical dipole. The errors introduced by inaccuracies in the antennas are discussed; it is shown that the measured inaccuracies might give errors on the order of ±0.05 in axial ratio and polarization fraction. The observed polarizations are similar to what has been reported by other observers, so qualitively there is no gross "bandwidth effect." Mixed and variable polarizations have been seen. An example of a mixed polarization record is shown.