OK I'm confused.
All the AM radio stations registered with FCC publish curves showing 2.5, 0.5,
and 0.15 mV/m contours. I'm assuming these are field strengths on the ground
e.g. low angles.
http://radio-locator.com/cgi-bin/pat?call=WGN&service=AM&status=L&hours=U
I always thought that these were based on models of local terrain/ground
conductivity and antenna patterns with some cross-checking against real
measurements (E.g. selective voltmeters).
Many of the AM stations have very "interesting" coverage patterns due to local
and distant variations in ground conductivity as well as beam patterns formed
by phasing multiple towers so these patterns on not done just by
seat-of-the-pants.
Is 160M so bizarre that the same electromagnetic principles (used for half a
century to carve up AM frequency allocations across the US and Canada) are not
applicable to finding field strength on the ground for 160M ham stuff?
Tim N3QE
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Topband reflector - topband@contesting.com
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