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## [TowerTalk] Crossed Dipoles....

 To: [TowerTalk] Crossed Dipoles.... W8JI@contesting.com (Tom Rauch) Mon, 12 Jul 1999 08:54:51 -0400
 ```Hi Gary > You must be using proportional font (or someone else is and is > complaining about it). Non-proportional is the "rule" for news and > E-mail. Some programs default proportional. That sounds to me like Maxwell's equations must sound to others. I know nothing about computers, and dislike hearing people talk about them. I'm an appliance op when it comes to computers, although I appreciate your trying to help (I'm beyond help on that topic). > I assume the 90 degree phase shift can be done with a 1/4 wave line > section at the center. I think I've seen that in a handbook or antenna > book over the years. Yes. This goes back to things like the dreaded Inverted L thread. If you bend an antenna and that's all you do, you don't wind up with both patterns. You wind up with ONE pattern that is the vector sum of the two. So if I put up a perfect Inverted V dipole, broadside to the V I have a perfect horizontal pattern. Not a mixture of V&H. An inverted Vee dipole, just like regular dipole, radiates a vertically polarized wave at high angles off the ends. An inverted L half-wave fed in the center, broadside to the L, produces a tilted wave that is neither vertical or horizontal and still has a response null at 90 degrees to the main response. The crossed dipoles, unless you feed them in phase quadrature, give a pattern JUST like a single dipole that is rotated 45 degrees to either pair. It is still (if the antenna is high enough) a dipole pattern with two lobes and two nulls. So you must use a 90 degree phase delay between the two dipoles, or you made the same pattern change you would have made by simply turning a single dipole antenna to a new direction. The phase shift isn't critical, anything between 60 and 120 degrees would make a pretty much omni pattern, but you must use the phase shift or you won't have the omni pattern. > Thanks for the wisdom, Tom. I had always wanted to try something like > that but had forgotten about the phase shift. I'm wondering how well it > would work if the two dipoles were cut for opposite ends of the band (i.e. > 3550/3900)? Since the system isn't current or phase critical, it should be OK. 73, Tom W8JI w8ji@contesting.com -- 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 ```
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