Notes on propagation

These notes are intended as a brief discussion of the fading which occurred during an extended microwave propagation experiment, operated at a frequency of 4000 Mc. Several similar tests have been conducted in recent years and have yielded considerable information concerning the behavior of microwave signals under the influence of varying atmospheric conditions. Although the test under consideration was conducted under conditions very much similar to earlier tests, there were two important differences. First, the present test included spaced diversity reception whereas in earlier tests diversity reception was not employed. Simultaneous recordings of both main and diversity signals afforded means of fade-by-fade comparison and provided data for a general analysis in determining the effectiveness of diversity action. Secondly, earlier tests were made with an rf power output in the neighborhood of 0.1 watt at 4000 Mc, whereas in this more recent test a cw type magnetron delivered approximately 10 watts at the same frequency. The hundredfold increase in output power added 20 db to the depth of the measurable fade.