No expertise here.
W3AHL did modeling for me, base on some experience, available trees, etc.
Starting point was that I wanted a T top, with top 130 ft long, fed with window
line, not shorted at the top.
I pulled a line where the antenna was planned to go, with a tape measure
dropped from the middle.
Long story short:
57' window line vert. element
130 ft 14 ga copperweld horiz. element, open in center, connected to feedline.
Four 75ft 11 ga Al radials, 7 ft above ground, tied together and fed with about
six uH of coil to coax shield.
Each radial was run, with the coil, against the vert. element and trimmed to
1820 KHz.
This ant is great. At 800W, it really gets out, working VK easily when open.
EU on 100W no prob.
Z is about 35 Ohms and shack SWR 1.3, no tuner needed, fed with a pi net.
NOTE: The coax feedline to the shack was a big disruptor of the system,
completely cured with some big clamp on ferrites.
Three turns through double large toroids worked too.
More people hear me than I can hear, so I know I need some Beverages, but have
been too lazy to put them up.
The punch line:
The open top and window line, fed with an L network at the bottom and 200 ft
coax to shack, make a great 80m dipole!
Unfortunately, it's oriented E-W, so not a great orientation for 80, but even
so it easily works EU at 45 deg off axis.
The feedpoint is a garden post and there is a 1/4 inch poly rope strength
member from the ant center to an insulator screwed into the post, to keep wind
from causing tension in the window line.
This antenna is the best, most planned, of any I've ever had! It's been up
since Bouvet Island did not get on 160m. Thanks Steve!
WL
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