Wireless Echoes from Regions above the F Layers

Abstract

DURING recent years, we have obtained a large number of fixed-frequency continuous automatic records of the cyclic changes of effective layer-heights which constantly occur in the ionosphere, and our record files now cover a period of approximately 11,000 hours. Our most interesting results have been obtained at the frequency of 3,492.5 kilocycles, although we have also made a number of experiments on the simultaneous reception of 4,095 and 2,398 kilocycles. Some of the 3,492.5 kilocycle transmissions have been recorded simultaneously at three different geographical points. The receiving and recording apparatus is compact and reliable, and it can operate at a distant point for at least two weeks without any attention. An accurate time scale is automatically marked on all records by the transmitter.