Aspects of HF radio propagation

E. Michael Warrington, Alain Bourdillon, Eulalia Benito, Cesidio Bianchi, Jean-Philippe Monilié, Martha Muriuki, Marco Pietrella, Hanna Rothkaehl, Veronique Rannou, Stephane Saillant, Ozgur Sari, Alan J. J. Stocker, Ersin Tulunay, Yurnadur Tulunay, Nikolay Y. Zaalov


radio systems. From the point of view Working Group 2 of the COST 296 Action, interest lies with effects associated

with propagation via the ionosphere of signals within the HF band. Several aspects are covered in this paper:

a) The directions of arrival and times of flight of signals received over a path oriented along the trough have

been examined and several types of propagation effects identified. Of particular note, combining the HF observations

with satellite measurements has identified the presence of irregularities within the floor of the trough that

result in propagation displaced from the great circle direction. An understanding of the propagation effects that

result in deviations of the signal path from the great circle direction are of particular relevance to the operation

of HF radiolocation systems.

b) Inclusion of the results from the above mentioned measurements into a propagation model of the northerly

ionosphere (i.e. those regions of the ionosphere located poleward of, and including, the mid-latitude trough)

and the use of this model to predict the coverage expected from transmitters where the signals impinge on the

northerly ionosphere.

c) Development of inversion techniques enabling backscatter ionograms obtained by an HF radar to be used

to estimate the ionospheric electron density profile. This development facilitates the operation of over the horizon

HF radars by enhancing the frequency management aspects of the systems.

d) Various propagation prediction techniques have been tested against measurements made over the trough

path mentioned above, and also over a long-range path between Cyprus and the UK.

e) The effect of changes in the levels of ionospheric disturbances on the operational availability at various

data throughput rates has been examined for the trough path mentioned earlier.

The topics covered in this paper are necessarily brief, and the reader is referred to full papers referenced

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X