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shorty forty on the tower. (If you do, have a conversation with N4ZR about what happened to the performance of his F12 forty when he got rid of all the metal guys.) You helped yourself by insulating from the tower. You probably got lucky with the length of the 54' sections to the ground. You ARE coupling power into the guys. Absolutely no doubt about that. It may be doing some interesting things to the pattern, but you say the SWR is not affected any more on 15. SWR hardly measures everything going on in that system. It's just the most common complaint cause everyone has a meter. If there was some magic viewer that we could see the RF pattern, like an infrared viewer for RF or something, SWR would be the LAST thing to be complained about. This is not a hard thing to model. It's just some wires in space. The NEC4 high-priced rocket science stuff not needed for this one. The question is whether there is significant current in the guys. Having significant current does NOT mean that the SWR MUST be affected. You CAN have an enormous SWR change. You can have a significant pattern screw-up without SWR change. It just depends. Bad things like destroying the antenna's rejection of vertically polarized signals. That can make the antenna a lot noisier, can cause TVI, and a nice list of baddies. It may add up just right so that there's no SWR change. You could have a trouble with one of the elements that you don't know about yet, and the effect of the guy wires is to cancel it out. The ends of the guy wires are just a few feet below the antenna, directly in the NEAR field, where the radiation from the elements has not yet formed the familiar FAR field pattern. If you insist on using insulators and big grips as the only solution (because they are cheaper to ship???) then you need to break up the 54 feet into 11, 11, 11, 21, top to bottom. That's nine insulators and 18 big grips. The high 11' sections MUST be insulated from the tower. The alternative (that you don't want to hear) is to get 100' (that's all) of Philly, cut it into three 33' sections, only SIX Philly grips. Put the upper Philly grips direct to the tower, the bottom Philly grip to a big grip on the remaining steel (no insulators needed). That will put the wire 33' down and away from the C31, and hugely minimize any guy effect. And you're going to tell me it's cheaper to ship nine insulators and 18 big grips than 100' of Philly (weighs the same as rope) and six Philly grips? Or maybe you got the insulators and the grips laying around. The Philly sure looks better. Whatever. Best of luck & 73. Guy. ----- Original Message ----- From: "Sylvan Katz" <jskatz@sk.sympatico.ca> To: "towertalk" <towertalk@contesting.com>; <Force12Talk@qth.com> Sent: Tuesday, July 23, 2002 3:47 PM Subject: [Force 12 Talk] C31XR & guy wire detuning > Hello All > > I am trying to solve a guy wire problem - they seems to be detuning my > C31XR. Last year when I installed the antenna I found I could not get the > swr down to the spec level on 15 and 20. Natan suggested that I my guys > could be detuning the XR. This summer I inserted insulators right at the top > of the tower. This brought 15m right on spec! Great! > > I am still having problems on 20m - the minimum swr is about 400 khz too > high. The bottom sections of each guy is about 54' long. Natan suggests that > the capacitance caused by the insulators and subsequent following wire > lengths can easily move the resonance of the 54' to a length near 62 feet > which is nominally a full wave resonator on 20 meters. > > I want to break the 54' sections into two segments each. My question: > > What should the lengths of these two sections be to minimize their > interaction with the C31XR? > > .. sylvan > > ps - please do not recommend the use of Phyllistran -- it is too costly to > have it shipped here :) > > > Ô¿Ô¬ > ---------------- > Sylvan Katz, VE5ZX > Saskatoon, SK > "A Novel Perspective of Amateur Radio Contesting" at > http://www.dynamicforesight.com/~ve5zx > > > > -------------------------------------------- > Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. > Force12 Web Site: http://www.force12inc.com > > To Submit Message to the List: Force12Talk@qth.com > To unsubscribe and view the Message Archive: see http://qth.com/force12/list > For problems with the list: contact n4zr@qth.com > > -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact n4zr@qth.com |