Abstract
Large deviations in the direction of arrival of ionospherically propagating radio signals from the Great Circle Path (GCP) have serious implications for the planning and operation of communications and radiolocation systems operating within the HF-band. Very large deviations are particularly prevalent in the polar and sub-auroral regions where signals often arrive at the receiver with bearings displaced from the great circle direction by up to ±100° or more. Measurements made over several paths are presented in this paper, and the principle causes of off-great circle propagation outlined. Significant progress has been made in modelling the propagation effects and work is now in hand to incorporate the results into tools to aid the planning and operation of HF radio systems operating at northerly latitudes.
Highlights
Large deviations in the direction of arrival of ionospherically propagating radio signals from the GreatCircle Path (GCP) have serious implications for the planning and operation of communications and radiolocation systems operating within the HF-band
Significant progress has been made over the COST 271 period and the aim of this paper is to summarise the important results of this research, to consider work in progress aimed at further improving our understanding of the high latitude propagation mechanisms, and to report on methods being developed for taking these propagation effects into account when designing and operating HF radio systems
During the winter and equinoctial months, there is an underlying tendency for propagation to deviate to the west of the great circle path in the evening sector with propagation returning from the east of the Great Circle Path (GCP)
Summary
Circle Path (GCP) have serious implications for the planning and operation of communications and radiolocation systems operating within the HF-band. The situation is further complicated since, in addition to the large scale tilts which cause gross deviations of the signal from the great circle direction, irregularities in the electron density distribution cause signals associated with each propagation mode to arrive at the receiver over a range of angles in both azimuth and elevation. Such directional spread of the received signal energy is an important parameter to be considered in the design of multi-element receiving arrays and the associated signal processing methods used, for example, in radiolocation or adaptive reception systems. The discussion of individual aspects in this paper is brief and the reader is referred to several papers which consider individual topics in more detail
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