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How does shoreline effect led to fluctuate the needle of the ADF ?

Asked by: 2840 views General Aviation

why when we are flying from land to sea or from sea to land shoreline effect causes to fluctuate the needle of the ADF?

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2 Answers

  1. Aleks Udris on Feb 17, 2014

    Reza – Great question!

    Radio waves refract, or bend, when the density and composition of the air changes.

    The air density of air and composition (amount of water vapor, etc) differs over land and water – land is dryer, and during the day, generally warmer (less pressure). Air over a large body of water is is more humid, and during the day, generally cooler (more dense).

    So, you really have two different air masses that meet at the shoreline. When radio waves move across the boundary between these masses, their speed changes and they bend.

    The radio waves bend the most when they cross in a nearly parallel angle, and the least (or not at all) when they cross the boundary at a perpendicular angle.

    There’s not a lot of great examples out there to answer this question, so I’ll put out a blog post about this on Thursday over at http://www.boldmethod.com, and I’ll try to include a video. Check it out!


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  2. reza zare on Feb 17, 2014

    Aleks Udris
    thank you very much for your answer.your answer really helped me and I am looking forward to see your post on Thursday .

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