An up-converter solar radiospectrograph for the frequency range 200-2000 Mc/s

A very wide-band solar radiospectrograph employing an untuned parametric up-converter is described. The receiver has a noise figure of 9.0-12.5 dB and, in conjunction with a 30-foot-diameter parabolic aerial with log-periodic feed, is capable of detecting the thermal background radiation of the quiet Sun over a continuous single-band frequency coverage of 200-2000 Mc/s. Problems in the design of untuned parametric up-converters are discussed, and measurements made on the equipment described show that the gain is much greater than that predicted by the "three-frequency" theory of parametric amplifiers, although no provision has been made to optimize the loading for the idler frequency component. This type of receiver is capable of further development both as regards increased sensitivity, extension of the frequency range, and application to different parts of the radio spectrum. Examples of spectra of solar outburts in the range 200-2000 Mc/s are given.