Page:Open Skies (Kellermann).pdf/29

 Fig. 1.3 Karl Jansky examining the output of his paper chart recorder. Credit: NRAO/AUI/ NSF

At the April 1932 Washington meeting of the US National Committee for the International Union of Radio Science (URSI), Jansky presented a paper on “Directional Studies of Static on Short Waves,”12 which he later published in the Proceedings of the Institute of Radio Engineers (Proc. IRE). In this, the first of his three classical papers, Jansky (1932) described in some detail his antenna and receiving system and reported that he had found three distinct groups of static.

he first group is composed of the static received from local thunderstorms and storm centers. Static in this group is almost always of the crash type. It is very intermittent… The second group is composed of very steady weak static coming probably from [ionospheric] refractions from thunderstorms some distance away. The third group is composed of a very steady hiss type static the origin of which is not yet known.

Jansky then goes on to discuss the crash type static in some detail, but adds, The static of the third group is also very weak. It is, however, very steady, causing a hiss in the phones that can hardly be distinguished from the hiss caused by [receiver] noise.

He remarks that he did not recognize this third type of static until January 1932, but he was able to go back to reexamine his earlier data and recognized that