[TowerTalk] Bead chokes on feedlines; K3LR array

[Pete Smith <n4zr@contesting.com>]

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
The World HF Contest Station Database
was updated 20 Oct 2004
2796 contest stations at
www.pvrc.org/WCSD/WCSDsearch.htm  

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