[TowerTalk] A Capacitively Fed 102 Degree Vertical for 160 Meters

[Jim Brown]

On Sun,3/22/2015 4:56 PM, tedc at nucleus.com wrote:
> My design is based on the fact that at approximately
> 102 degrees of length a vertical should exhibit a
> feed point impedance of 50 +j100.

I've been using essentially this technique with my primary 160M vertical 
since 2007. Until this fall, it was 86 ft vertical with enough top 
loading to bring the feedpoint Z to 50 +jX. Then my tree guy told me 
that I needed to cut down the tree that held up one end before it fell 
on my water tank and broke it, so he moved it to a taller tree that made 
the vertical height 100 ft. The horizontal wire is now 82 ft.

To broadband it, I made the vertical portion two #10 copper spaced about 
10 inches apart. It measures better than 1.5:1 up to about 1.9 MHz, and 
still loads well above that. I'm a contester and DX chaser, work SSB 
only in contests, so that's plenty good enough for me. :) A tower, of 
course, is a physically larger conductor, so will be even more broadband 
than my wires. Also, the value of jX when R hits 50 ohms well depend on 
the form factor (all vertical or top loaded), your radial system, and 
your dirt.

73, Jim K9YC