Noise in Maser Amplifiers-Theory and Experiment

This paper contains a theoretical treatment of noise in maser amplifiers and the results of experimental measurements of the noise of an ammonia beam maser. The concept of "effective input noise temperature" is defined and used. The theoretical treatment obtains an equivalent microwave circuit and derives expressions for the gain and effective input noise temperature of both reflection and transmission-type masers. The experimental measurements yielded values of about 80°K for the effective input noise temperature of a reflection-type ammonia beam maser. The experimental values agree with those predicted by theory and the comparison of experiment and theory gives an upper limit of about 20°K for the magnitude of the "beam temperature."