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## [TowerTalk] RE: TowerTalk Digest, Vol 23, Issue 101

 To: [TowerTalk] RE: TowerTalk Digest, Vol 23, Issue 101 "Dudley Chapman" Mon, 29 Nov 2004 23:49:50 -0500
 ```Jerry, Radials on the surface do not need to be 1/4 wavelength long since they don't serve to resonate the structure like elevated radials do. They are there to improve ground conductivity only. Radials between 1/8 and 1/4 wavelength are considered optimum. So on 40m, even your 10 foot radials are not far from that range and would be useful. Your 60 foot ones may even be longer than they need to be. After 1/4 wavelength, you are beyond the point of diminishing returns. However, there is no harm in any of the radial lengths you propose. There may be some directivity but I bet it would be very hard for you to detect it. As for the number of radials, there is a rule of thumb that says you reach a point of diminishing returns when the distance between the tips of two adjacent radials is less than .02 wavelengths or so (assuming they or equal length). Any closer than that does little additional good. So that implies that you will actually have fewer 10 foot radials per degree than you have 60 foot radials per degree. It seems odd, but it's all about the density of wire over the surface area. At only 10 feet from the base of the antenna, you don't need many wires to make up the required density. So for 40 meters, plan for 0.02 x 40m = 0.8m or approx 2 1/2 feet between the tips of the radials regardless of length. (For grossly unequal length radials, this means 2 1/2 feet between the tip of the shorter radial and the closest point on the adjacent radial.) The other important point is that the current density in the ground has the same distribution as the vertical, so your 10 foot radials are at least in the right place to reduce some losses. If you have no ability to lengthen the shorter radials, they will be less useful on 80m and 160m, of course. But like everything else in ham radio, we do what we can do within the limitations and make the best of it. I, for one, would consider building an 80m or a 160m vertical for the radial field you propose. I am inclined to think that at 40m you are on the high frequency end of the range where a vertical can outperform a horizontal antenna. Verticals are good to use when you can't get a horizontal antenna high enough. But on 40m, you might be able to get an inverted vee high enough to outperform a 40m vertical. Its just a thought. Regards, Dudley - WA1X Date: Mon, 29 Nov 2004 17:50:03 -0500 From: "Jerry Keller" Subject: [TowerTalk] Uneven Radials To: "(Reflector) TowerTalk" Message-ID: <012e01c4d665\$c6cc5f60\$6400a8c0@homebrew1> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Gentlemen: For a 40M 1/4 wave vertical at one end of my back yard, I have room for radials on the surface to run out 60' to the west, 30' to the east, 25' to the north, and only10' to the south. I'm in eastern PA, and the earth here has pretty good conductivity. (1) Should I expect any directional consequences? I would think so, but in what directions? (2) I had planned on 60 radials evenly spaced. Would it help to have extra radials in the directions with the shortest runs? (3) How would the answers be different for 80M? 160M? 73, Jerry K3BZ _______________________________________________ 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. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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