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  Scattering Ocean Waves and Working Range vs. Radar Frequency


The attenuation of the electromagnetic wave travelling along the sea surface depends on the radar frequency and on the conductivity (salinity) of the water. The table gives some estimates of working ranges for selected radar frequencies and water salinities. The values for 'Ropt' and 'Rmin' have been derived from 'Modern Radar Techniques, COLLINS, Editor: M.J.B. Scanlan, Chapter 5, Author: E.D.R. Shearman'.

The radar frequency must be selected carefully, taking into account the use of the radio spectrum by communication services. Long-term observations of the radio band coverage using a spectrum analyzer should be done before selecting a radar frequency. The working ranges given in the table are based on a clear frequency without interference. In any case, a radio transmit license is required prior to operating the HF radar.

The values for the highest possible range resolution of the radar are limited by the frequency bandwith (the width of the gaps in the radio spectrum) available at the different radar frequencies. They are derived from observations of the radio spectrum.

Finally, it must be checked that the Bragg-scattering ocean waves (PBragg and WBragg exist in area to be monitored. This may be critical in shallow areas, where long ocean waves 'feel' the sea buttom and are attenuated.

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