**Antenna SWR Problem**

Discussion in 'General Technical Questions and Answers' started by W0LC, Nov 27, 2003.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Tom, it sure would be interesting.

    This is an unguyed (crank-up) tower. The two legs of the inverted vee come down at visually identical slope angles from the apex, and the enclosed angle is (visually) 90 degrees. The coax bisects that angle and drops straight down to the roof of the house 40' below, then across the roof, down an outside wall and into the shack -- about a 160' run.

    I'm assuming something is interacting with something, but don't know what, and gave up caring several months ago. Possibly the coax running across the roof of the house, even though it's 40' below the antenna, is causing a problem. I realize that 40' is only about .15 wavelengths on 80m, but don't have any other reasonable way to route the feedline.

    Also, all my feedlines (coax ones, anyway) bundle at the tower/roofline interface, about 40' below the tower top; from that point to the shack wall, there are several cables running in parallel, occasionally taped together to hold them in a bundle. If there's common mode currents on the 80m inverted vee coupling to other stuff, that's surely possible; however, I've tried a pretty good current balun (RadioWorks B1-5K) at the feedpoint, and didn't see any difference with or without it.

    And, the cables are still bundled when I crank the tower down lower! The only thing that occurs at lower height is that the inverted vee comes into resonance and dips in the band...

    Any guesses-?

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