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Forward-Scatter Antenna Considerations

March 2nd Fact-of-the-Day

Ionospheric forward-scatter propagation makes communication possible beyond the horizon at frequencies above the normal maximum-usable frequency (MUF). However, high transmitter power is needed and high-gain antennas should be used on both ends to overcome high path losses. In addition to overcoming path losses, the increased directivities of high-gain antennas reduce reception of strong off-path-reflections from meteoric ionization, which, because of late arrivals, reduce communication bandwidth. Space-diversity receiving antennas placed in line with the normal signal path at a spacing of at least ten wavelengths will reduce fading. Antennas should be horizontally polarized to reduce scattering-propagation losses, because the ground reflection characteristics are more desirable, and to help discriminate against local man-made noise. ©2005 Martek International All rights reserved.


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