Absolute calibration method and technique of the daily patrol of the solar flux density at 1470 MHz

In the frequency range from 1 to 2 GHz discrepancies exist between the values of the solar flux density observed at several stations. In order to clarify the situation a new absolute calibration has been carried out by the HHI at 1470 MHz. The equipment used for this purpose consists of an electromagnetic horn with calculated gain and of a receiver, the temperature scale of which has been calibrated by comparison with the noise of a heated absorber. The noise temperatures of the absorber have been identified with the mean thermodynamic temperatures of the absorbing material. The calibration procedure of the receiver and the observation method of the sun's radiation are described. An error analysis is given in detail, including impedance mismatches of the microwave components as well as impedance variations of the heated absorber. A maximum uncertainty of about ± 1.7% is calculated.