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RF range - plane earth model

Discussion in 'Electronic Design' started by Ian, Aug 18, 2003.

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  1. Ian

    Ian Guest

    G'Day all,

    Can anyone give me the quick summary as to why the plane eath RF
    propogation model doesn't include a frequency term?

    I have seen a reference that the plane earth model is pretty much only
    useful in the UHF band and hence maybe the freq term becomes
    insignificant, that is the additional loss introduced by frequency
    does not vary much over the UHF range. Is that the reasoning?

    http://www.radioinnovation.com/Howto/how_far2.htm gives some details
    but it bothers me that freq doesn't come into it.

    My application is *not* inbuilding so I am not using one of the more
    elaborate scattering models. However, my antenna heights are
    potentially quite low, so I suspect a simple plane-earth model will be
    somewhat optimistic, anyway.

    Thanks,
    Ian
     
  2. At longer wavelengths (frequencies around 2 MHz or lower) the wavefront
    loses energy due to currents induced in the Earth. This causes the wave to
    tilt forward and follow the Earth's curvature producing propagation
    distances well beyond the line of sight. Consider WWVB propagation at 60
    kHz.
     
  3. Hi,
    The complete expression has terms in lambda but the d^4 approximation
    is used when 'd' is large with respect to the antenna heights. Have a
    look at --


    http://www.wireless.per.nl:202/multimed/cdrom97/pel.htm


    Cheers - Joe
     
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