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[TowerTalk] Bead chokes on feedlines; K3LR array

Subject: [TowerTalk] Bead chokes on feedlines; K3LR array
From: Pete Smith <>
Date: Mon, 08 Nov 2004 14:42:25 -0500
List-post: <>
Tom's excellent message this weekend on use of current mode chokes on a feedline caused me to reflect on(no pun intended) my K3LR-type 80-meter array. It uses four dipoles arranged in a lazy-vee configuration. Because of space limitations, the dipoles' upper legs are straight, while the lower halves describe roughly a quarter circle in making their way back to the tower at about the 7-foot level. The feedlines for each dipole come back to the tower at roughly the 25-foot level, thence down to the switchbox near ground level.

When I built this array, I put 50-bead chokes at each feedpoint, thinking that I would help suppress common mode currenst and thereby avoid any destructive interaction with the antenna pattern. Now, however, Tom makes me wonder if this is useful at all, given that the feedlines are in the very near field of the dipoles anyway. Would I be just as well off to eliminate the chokes altogether, or do they serve a useful purpose, assuming they are of the right material and have enough inductance to do the job?

The antenna has been up and working pretty well for 6 years. I ask at this point because 2 of the 4 dipoles quit working at the start of Sweepstakes, and I'm thinking it is time to replace the feedlines before winter sets in further.

73, Pete N4ZR
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