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Northern Exposure 92: An Investigation of Transauroral HF Radio Skywave Propagation

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The primary objective of the Northern Exposure 92 campaign was to assist in the evaluation of the performance capabilities of a wideband, high frequency, Rake radio receiver on a transauroral skywave channel. A review of the data collected on the transauroral channel during the Northern Exposure 92 exercises indicates that one is likely to encounter three types of signals on the channel 1 a strong, specularly reflected signal characterized by the usual ionospheric dispersive delay spread and negligible Doppler spread, 2 strong specular multipath signals, exhibiting extensive delay and Doppler spread, and 3 weak scatter signals, exhibiting the widest delay and Doppler spreads. The nonspread reflected signals are encountered during magnetically quiet, daytime conditions where the ionosphere may be described as laminar. The strong, specular-multipath signals occur mostly at night and are associated with reflections from large scale irregularities of electron density characterized by strong horizontal gradients capable of reflecting signals whose frequencies lie below some equivalent maximum usable frequency MUF defined by the path, the background ionosphere, and the maximum electron density in the irregularity region. The weak scattered signals occur at night and are associated with volume scatter from the irregular medium. The scattered signals present the greatest challenge to communication systems with amplitudes approx. 30 dB less than those of reflected signals and with 2 sigma Doppler spreads as large as 30 Hz. HF skywave, Pulse sounder, Propagation, Channel characterization. Wideband communications,

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  • Radio Communications

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