FM and SSB Radiotelephone Tests on a VHF Ionospheric Scatter Link During Multipath Conditions

Experiments have been carried out on an ionosphericscatter link to observe the effects of long-delayed multipath signals, caused by F
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propagated back scatter, on the intelligibility of voice communication. Frequency modulation and single-sideband modulation equipments were used for the tests. During periods when the back-scatter signal levels approached the level of the normal ionospheric-scatter signals, the frequency-modulation voice transmissions were unintelligible; however, under the same conditions, single-sideband voice communication intelligibility remained at almost 100 per cent although there was some loss in quality.