Topband: Hindering factors in the science of back yard 160m vertical
rfry at adams.net
Thu Nov 10 02:28:55 PST 2011
Brian Machesney wrote:
>I'm confused by your assertion that, "The [BL&E] data gathered is
>applicable to other frequencies for antenna systems having the same
>conductor dimensions in wavelengths. Your paper titled,
>"Frequency and Earth Conductivity as Factors in MW Field
>Intensity" indicates that frequency has a pronounced effect on field
The data taken by BL&E applies to different conditions than the data plotted
in my paper.
The BL&E data shows the groundwave field from monopoles where the
propagation path is so short that the affect of earth conductivity and
frequency were/are negligible. That was their intent, as they wanted to
determine antenna system performance as a field generator, only, and did so
by measuring the groundwave field from each over that short path when the
power applied to each system was held constant.
My paper shows how such groundwave fields THEN are affected by various
(long) propagation paths, MW frequencies, and applied powers over earth of
different conductivity values, for series-fed 1/2-wave monopoles using a
very low-resistance connection to r-f ground (2 ohms).
So my paper is based on a fixed field intensity measured a short distance
from the monopole, rather than a varying field depending on the monopole
height, and the configuration of buried radials it uses.
>Further, you write that, "Groundwave radiation in the AM
>broadcast band... can penetrate the earth to the depth of
>several tens of meters." .... Would your assertion not be true
>only in the case of earth which is homogeneous with respect
>to conductivity to a depth of several tens of meters?
My assertion would be true for any combination of conductivities in that
soil depth and over those path lengths that produced a net conductivity that
can be described by a single value. My paper was focused on effects other
than the variation of earth conductivity with depth and path length.
Thank you for your comments.
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