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 To: [TowerTalk] Ground Radial Fields n7cl@mmsi.com (Eric Gustafson) Sat, 27 Mar 1999 11:11:15 -0700
 ``` Hi Clive, If this is your 40 meter antenna, it is already working pretty well. I'm assuming (since you didn't specify) that you are talking about the radial field surrounding the base of a full size or near full size 1/4 wavelength _vertical_ radiator. I'm also assuming that you are talking about radials which are on the earth's surface or just below it. In that case (we're already two assumptions down at this point), the screen density you describe is sufficient for a radial length of only about 1/4 wavelength (thus generating a third assumption by inference). Depending mostly on the initial state of the local ground conditions and radial system (also unspecified), improving one half of a radial field with a radius of 1/4 wavelength may or may not get you a few dB of improved efficiency. But any improvement will apply nearly equally to all parts of the pattern. There will be a small effect on the TOA and total energy in the pattern in the direction of the improved ground. But the difference (compared to other directions) will be largely insignificant. To really do TOA lowering by improving the ground around a full size vertical, the ground must be improved for a great distance out (3 to 8 wavelengths depending on your goals). The required radial density for 3 wavelength long radials is much higher than for 1/4 wavelength radials. For example, a 3 wavelength radius radial field with a screen density at its outer edge equivalent to a 1/4 wavelength radius field with 120 radials would require approximately 1260 radials. I normally apply a "relevance loss" of 3 dB per assumption to the information transferred as it relates to the specific instance actually being discussed. So you should bear in mind that this may only apply to your installation to within about -9 dB. ;-)... Or it might be dead on - IF the assumptions were OK. 73, Eric N7CL >From: "Clive Penna" To: >Date: Sat, 27 Mar 1999 11:42:26 -0000 > >HI, Does anyone have any field strength data, re the lowering of >radiation angle in a given direction if extra radials are >concentrated in that direction. ie taken to the extreme 60 >radials covering 180deg whether that arrangement would have the >performance of 120 radials at the mid way point,and the >radiation angle increasing as you run out of radials. 73 Clive >GM3POI -- FAQ on WWW: http://www.contesting.com/towertalkfaq.html Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com Search: http://www.contesting.com/km9p/search.htm ```