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I made a mistake about ADF navigation which is involving my mind When does twilight effect occur? Just before an just after sunrise or sunset, what does it mean? Before and after sunrise and before and after sunset, or, just before sunrise and just after sunset, or , the period between sunset and sunrise? When exactly do we have twilight effect?

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1 Answers

  1. Wes Beard on May 15, 2014

    From http://www.awomansplaceisinthecockpit.com/adf/

    Twilight/night effect. Radio waves arriving at a receiver come both directly from the transmitter – the ground wave – and indirectly as a wave reflected from the ionosphere – the sky wave. The sky wave is affected by the daily changes in the ionosphere, read the ionisation layers section in the Aviation Meteorology Guide. Twilight effect is minimal on transmissions at frequencies below 350 kHz.


    My best guess is just before sunrise and just after sunset. Whenever the frequency of the wave is such that it can bounce off the ionosphere and meet its corresponding ground wave at the same time. I’m sure the times change for a change in frequency.

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