A bolometric noise generator of the through type built into a horn antenna

Abstract

It has been proposed [i, 2] to usewaveguide bolometric transformers of transient power as UHF noise generators. It has been shown that bolometric noise generators (BNG) in the centimeter range can be attested as standard independently of other means of radio noise measurements with a maximum error of 5% at an excess noise temperature AT n of up to 33 K. However, existing standard thermal noise generators permit lowering this error by less than up to i% [3]. Therefore, to use BNG as independent standard gauges is scarcely expedient. However, considering that BNG have certain quite useful properties, for example, a rather low inertia and the possibility of monitoring AT n through filament resistance, it is evident that it is worthwhile to consider the question of using BNG as secondary gauges of increase in noise temperature &T n (noise contrast). Thus, BNG may be used as a through gauge of increase in ~T n built into the input circuit of a radiometer. Since the loss introduced by such a BNG should be small, AT n cannot exceed several Kelvins. Nevertheless, if the radiometer into which the BNG is built is highly sensitive, this is entirely sufficient to monitor the calibration of the radiometer for noise contrast with good accuracy.