Cosmic Radio Noise Intensities in the VHF Band

During 1948 and 1949, the National Bureau of Standards conducted continuous, broad-directivity measurements of the cosmic radio noise intensities at frequencies between 25 and 110 mc. Their purpose was to evaluate the importance of this noise from the standpoint of its interference with radio communication. The results show a regular daily variation in noise corresponding to the movement of the principal sources of cosmic radio noise across the antenna receiving pattern. This normal cosmic noise intensity pattern was found to be constant within the limits of the accuracy of the measurements. It was found convenient to present the results in terms of daily maxima and minima which bracketed the daily variations. No measurable change in these limits was observed in the course of these measurements. Besides the normal cosmic radio noise, penrods of abnormal high noise levels, generally associated with periods of unusual solar activity, were observed and recorded.