Topband: Ground screen
k6dgw at foothill.net
Sun Jun 15 17:41:00 EDT 2003
The primary purpose of the ground radial system is to return the ground
currents to the feedpoint with as low a loss as possible. Thus, the #1
first order rule is "more radials are better." Current magnitude tends
to increase as you approach the base of the antenna, thus the #2 first
order rule is, "more short ones are better than a few long ones, if
that's your tradeoff." There are a multitude of second and higher order
Ground screens are a lot of work, and I'm not qualified to assess their
value over radials quantitatively, but I can tell you that every AM
broadcast station I ever worked for, or saw, used radials. So does the
USCG at Loran-C stations (meny watts at 100KHz)
I have no advice for you on what will last 40 years buried in the
Scott Johns wrote:
> In an effort to not reinvent the wheel, I am interested in the group's
> experience regarding ground screens.
> I still have no idea what transmitting antenna system I will ultimately
> decide upon at W3TX (and chances are I will try many over the years).
> Nonetheless, all of the options share the common need of a ground screen
> for best performance.
> So I envision first building a 9 acre ground screen (an area large
> enough to accommodate the long term imagination) with a 40 year lifespan
> (to take me through retirement).
> 1). Are there any drawbacks to installing the groundscreen in a
> rectangular pattern (with all crossing wires cadwelded) rather than the
> typical radial pattern?
> 2). Would you use wire spacing any smaller than the 2.4 m advocated in
> Low Band Dxing 3rd edition chapter 9 section 2?
> 3). For a 40 year lifespan what type/size of wire would be best?
> 4). Any other suggestions you might make if such a project was in your
> Best 73, Scott W3TX
> W3tx at arrl.net
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> Topband at contesting.com
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