thanks Mr Fry for posting this interesting graphic.
Just to clarify: 60 radials are 1/4 wave and 60 radials [appear to be] 1/8
wave, is that correct?
73, K3VAT
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Message: 3
Date: Tue, 1 Jul 2014 05:33:21 -0500
From: "Richard Fry" <rfry@adams.net>
To: <topband@contesting.com>
Subject: Topband: Affect of Unequal-length Buried Radials on Monopole
Radiation Patterns
Message-ID: <6DAF464A56C14D45A843BED5D592B464@ToshLaptop>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
>Here is a clip of a post I made on another website in answer to a question
>there, which might be of interest here also...
Below is a link to a graphic from a NEC4.2 study showing how unequal-length
buried radials affect the groundwave fields of a 1/4-wave monopole, for
approximately the conditions given in the opening post.
The h-plane fields are uniform +/- 0.014 dB.
The ~304 mV/m groundwave fields calculated by NEC over these real earth
paths are rather close to the ~306 mV/m inverse distance field
("efficiency") that the FCC predicts for this power and distance for a
1/4-wave, base-fed monopole driven against 120 buried radials, each 1/4-wave
in length.
Changing earth conductivity in that NEC model to 1 mS/m d.c. 5 (other
parameters the same) changes the groundwave field to about 259 mV/m at 1 km,
with a circularity of about +/- 0.12 dB.
http://s20.postimg.org/vn85ii9kd/Monopole_Unequal_Length_Radials.jpg
R. Fry
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