|Subject:||Re: [TowerTalk] Radials Questions - 270 or 360 degrees.|
|From:||Bill Coleman <firstname.lastname@example.org>|
|Date:||Wed, 5 Jan 2005 19:08:11 -0500|
On Jan 5, 2005, at 11:50 AM, Red wrote:
EZNEC modeling indicates a very slight assymetry and reduction of gain resulting from omitting 90 degrees segment of the radials. Both figures are within the inaccuracies associated with errors and assumptions in the modeling.
Is 1.1 dB considered very slight?
The assymetry, 1.1 dB, can be reduced to 0.2 dB by removing the opposing 90 degrees of radials, at the cost of about 0.5 dB of maximum gain.
This doesn't seem like a good idea, then. The net change would be to increase the gain in the assymmetric direction by 0.3 dB, at the cost of 0.5 dB elsewhere in the circle....
The performance will benefit some from using more radials, even if, in the interest of limiting the amount of wire used, some are shorter than 60 feet. However, variables associated with modeling errors, assumptions of ground characteristics, terrain features, wires and pipes in the structure, etc. are generally greater than the calculated differences in performance. Put down as many radials as you can and don't worry much about the 90 degree gap. If you can fill the gap without introducing excess interference or complexity, do it.
Well, that about answers my first question -- how about the other three questions?
Question 2: In looking at option B, is the vertical segment going to have an adverse effect on the pattern in the NW to NE direction? Is the vertical segment going to change the phase of the currents and ultimately destroy any gains by adding the radials?
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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