Newnes Radio and RF Engineering Pocket Book, 3rd Edition

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paths: the long path (major arc) and the short path (minor arc). In

general, the best reception occurs along the short path. In addition,

short path propagation is more nearly ‘textbook’, compared with long

path reception. However, there are times when long path is better, or

is the only path that will deliver a signal to a specific location from

the geographic location in question.

Grey line propagation

The Grey line is the twilight zone between the night and daytime

halves of the earth. This zone is also called the planetary terminator.

It varies up to +23 degrees either side of the north–south longitudinal

lines, depending on the season of the year (it runs directly north–south

only at the vernal and autumnal equinoxes). The D-layer of the iono- ...