Extra Class question of the day: Propagation and technique: trans-equatorial, long path, gray-line; multi-path propagation

There are a number of interesting types of propagation that occur on the HF bands.  They include transequatorial propagation, long-path propagation, and gray-line propagation.

Transequatorial propagation is propagation between two mid-latitude points at approximately the same distance north and south of the magnetic equator. (E3B01) The approximate maximum range for signals using transequatorial propagation is 5000 miles. (E3B02) The best time of day for transequatorial propagation is afternoon or early evening. (E3B03)

Long-path propagation is the type of propagation that occurs when the longer of the two direct paths between stations is better for communications than the shorter path. The type of propagation that is probably occurring if an HF beam antenna must be pointed in a direction 180 degrees away from a station to receive the strongest signals is long-path. (E3B04) 160 to 10 meters are the amateur bands that typically support long-path propagation. (E3B05) 20 meters is the amateur band that most frequently provides long-path propagation. (E3B06)

Gray-line propagation can be described as long distance communications at twilight on frequencies less than 15 MHz. (E3B11) Gray-line is the type of HF propagation is probably occurring if radio signals travel along the terminator between daylight and darkness. (E3B08) Gray-line propagation is most likely to occur at sunrise and sunset. (E3B09) Gray-line propagation occurs because, at twilight, D-layer absorption drops while E-layer and F-layer propagation remain strong. (E3B10)

Another interesting propagation phenomenon is echoes. While not strictly a type of propagation, echoes are the result of propagation conditions. Receipt of a signal by more than one path is one condition that could account for hearing an echo on the received signal of a distant station. (E3B07)


  1. I am in the highlands of Scotland. Been thinking about getting my ham licence for some time after a bit of listening in over the years.

    Then early this week I was just scanning shortwave radio stations using my eton g3 s whip aerial when I picked up Radio Australia from their Victoria state transmitter. Plugged in my 40 foot horizontal roof top antenna and found reception loud and clear at a range of aprox.10,500 miles.

    I was aware of greyline but not sure of the detail so the next evening I Googled it and got up one of the interactive maps,switched radio to the right frequency-not a sound.
    Then just as the sun touched Australia as it became dusk here 57 degrees north just as if someone had switched it on Radio Australia came over loud and clear.

    So Ham licence is now definitely my ambition-you can have your I phone and keep it.

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