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#1
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Dr Artaud & DX Ace,
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#2
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The Tips can be Elevated above ground or
the Tips can be at/near ground level and a Ground Rod placed at both ends (Tips) with a Lightning Aresster (GDT) mounted on each. .................................................. ....... The higher the ends above ground, the better. You have less earth loss. There is no need to use lightning arresters at the tips of the dipoles to ground. If the wire were actually close enough to ground to arc to ground, it will do it, arrester, or not. Being as you are not protecting any devices at the ends, there is no real point in using arresters. The arrester should be in the feedline leading to the radio. If the inv vee is supported by a tree or mast, the lightning is more likely to take that path to ground, than the path of perpendicular antenna wires to ground. Lightning doesn't like to take sharp turns. So you should always ground the supporting mast well, if it's metal. It's gonna take the brunt of the strike to ground... Horizontal wire antennas are not near as prone to be a lightning target, as say a vertical, or other tall mast. IE: a dipole, or inv vee hung in a tree will add little to the overall likelyhood of that tree being struck. It would probably be struck anyway, antenna or not, if lightning was that close, to choose that target. I bet in most cases, the antenna would basically be untouched, unless the strike found the feedline running down the tree, and decided to use it....You can always snub the feedline to ground at the base of th tree in a case like that. I know I have had two direct strikes to my mast supported my various dipoles, and have never had any indication of wire, or coax damage. That tells me most of the strike is carried to ground by the mast, which does stick up about a foot above my antenna apex. "I currently have 160/80/40 dipoles on one feedline...Appx 440 ft of wire in the air...The apex about 42 ft high supported by a metal mast. So far, in 35 years of hamming, SWLing, I've never had a horizontal wire dipole be a lightning target. But mine are never higher, than surrounding objects, trees, etc unless supported by a mast, or tree, which then becomes a more preferred target than the dipole itself... Not saying it can't happen. It surely can. But not near as often as vertical targets. Even at 42 ft, I've still got trees taller than that in the yard... That helps...The last strike hit the tree in the front yard.... If the vertical target is well above the house, other objects, you can bet on it taking a zap sooner or later. Most people don't have wire antennas higher than the surrounding trees, etc, unless they have a vertical support to support it...When they get above the surroundings, is when their chance of a strike goes up sharply. Even horizontal metal can be a problem if it's really high...IE: beams, etc..MK |
#3
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#4
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![]() "? Dr. Artaud ?" wrote Thanks for the response. We just last night had another thunderstorm, depositing plenty of noise and lightning nearby. Our house is physically lower than the houses on either side, and the end of our yard has a very tall Silver Maple tree, to which my random wire antenna runs from the house. The wire ends about 7 feet from the tree trunk, and is tied to the tree with the rubber strip that is used to hold screens in windows frames. I fear that a strike to the tree will impart more than static to the random wire antenna. Perhaps you, RHF, Jack Painter, or others can comment on how to protect the random wire from transferring a lightning strike to the tree from following the antenna wire. As I sleep by the radio, I don't with to be awakened writhing from a lightning strike. Regards, Dr. Artaud In my opinion, the best lightning arrestor products for up to 1.5 kw transmission systems are made by Industrial Communication Engineers (ICE). Solutions for either open-wire (no coax feed involved) or coaxial feedline arrestors are shown at Array Solutions, the distributor for I.C.E. http://www.arraysolutions.com/Products/ice/3.html ICE also makes very convenient grounding blocks for the custom connections of coax shield grounding. This allows a "manifold" connection of several coax shield grounds to a ground rod and works very well. But Andrews and Harger and others also make those, and Harger is probably the best for grounding materials in general. Local electrical distributors will carry (or order) Harger products. Jack Painter Virginia Beach, Virginia |
#5
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"RHF" wrote in news:1113937736.278231.195640
@f14g2000cwb.googlegroups.com: Thnaks for your comments. Please see my response elsewhere in this thread concerning grounding needs. Dr. Artaud Dr Artaud & DX Ace, . The 'classic' Inverted "V" Antenna would usually have a combined Top Apex Angle of 90* to 120* or a Bottom Tip Angle of 30* to 45*. |
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