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Re: Topband: Testing Soil Conductivity

To: "TopBand List" <>
Subject: Re: Topband: Testing Soil Conductivity
From: w8av <>
Date: Tue, 9 Jun 2009 08:00:03 -0400
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The FCC M-3 Map, although used for predicting coverage and interference for AM 
broadcast stations at the application stage, uses theoretical soil conductivity 
data from the 1950's.  Although it will get you somewhat in the ballpark, the 
actual conductivity can vary a good deal from actual measured values.  For 
example, The M-3 map predicts the ground conductivity for North Central Ohio as 
8 mS/m.  In the summer months I have measured values as low as 4 mS/m and no 
higher than 6 mS/m in the winter months.  In Western Ohio the theoretical 
conductivity is predicted as 15 mS/m and the measured values agree closely with 
the theoretical ones.  So the map is an estimate which may or may not be 
totally accurate.

Since the FCC now requires most applications to be filed electronically, you 
may be able to obtain relatively recent and more accurate measured conductivity 
values from an AM broadcast 301 application filed for a station in your area (a 
301 application is an application for a construction permit for an AM Broadcast 
Station).  If you do a search of the FCC web site for AM broadcast applications 
in your area, you may be able to find the measured values in pdf attachments to 
the application.  That might give you some insight on ground conductivity 
values in you area.  The applications are all a matter of public record so you 
should have no trouble accessing and viewing them. Goose, W8AV
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