[600MRG] Ground Moisture Effects

[sbjohnston at aol.com]

Over my career I've observed the following points regarding AM broadcast antenna systems where the antenna match changed seasonally.  These antennas are usually full quarter-wave or greater verticals either alone or in a multi-tower directional array, but maybe what I've noticed offers some clues to the answers to your questions.

-  Sites varied greatly in the degree of seasonal change.  

-  Antenna base impedance measurements in various seasons showed more change in the resistance R value than the reactance X.

-  Upon closer inspection, sites with a larger seasonal changes often had either an eroded ground system or one antenna element in the array was shorter than the others (by design).  

-  Sites with a minimal seasonal changes seemed to have the best ground systems.

-  Rebuilding an eroded ground system usually improved seasonal change problems but usually did not eliminate it entirely.

 


 

Steve WD8DAS / WH2XHY

sbjohnston at aol.com
http://www.wd8das.net/
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