Accession Number : AD0285297

Title :   THE CORRELATION BETWEEN FREQUENCY-SELECTIVE FADING AND MULTIPATH PROPAGATION OVER AN IONOSPHERIC PATH

Corporate Author : STANFORD UNIV CA STANFORD ELECTRONICS LABS

Personal Author(s) : AMES, JOHN

Report Date : JUL 1962

Pagination or Media Count : 1

Abstract : The relationship between selective fading and the relative time delays of the various propagating modes is studied over the 2450-km path from Mayaguez, Puerto Rico, to Smyrna, Georgia. Selective fading was measured by propagating a FM-cw transmission over the path, while at the same time the modes propagating, and their structure, were recorded by means of oblique step-frequency soundings. It was confirmed that during periods when two modes were propagating at the FM-cw frequency, selective-fading nulls were separated in the frequency spectrum by an amount that is the reciprocal of the group time delay between the modes. Attention is drawn to the fact that the FM-cw technique represents an inexpensive means for determining the degree of multipath that exists on a given circuit at a given time. Such soundings, which can be made by simple modification of existing equipment, enable the degree of multipath to be quickly estimated, and also can give clear advance warning of impending circuit failure resulting from falling MUF. (Author)

Descriptors :   *IONOSPHERIC PROPAGATION, *MULTIPATH TRANSMISSION, *COMMUNICATION AND RADIO SYSTEMS, *RADIO SIGNALS, ATTENUATION, COMMUNICATION THEORY, FREQUENCY MODULATION, IONOSPHERE, MAGNETIC FIELDS, PROPAGATION, RADIO TRANSMISSION, RADIO WAVES, THEORY.

Distribution Statement : APPROVED FOR PUBLIC RELEASE