Since I have limited space for antennas, I was inspired by exactly that
Cebik article to build a vertical doublet cut for 20 meters, and am quite
pleased with the result. I used a 33' MJF telescoping fiberglas pole with
insulated 14 ga. wire fastened along its entire length with nylon tie wraps.
The wire was cut in the center and 450 ohm ladderline attached with a
ten-tec acrobat gizmo for strain relief. The pole is lashed to an 8 foot 4x4
planted in the ground about 20' from the house, with the bottom right at
ground level. I folded the lowermost 6 inches of wire back on itself to keep
it out of the dirt. The ladderline is run horizontally to the house, then
down to an outside mounted weatherproof current balun; from there a short
coax run leads through a window to the antenna tuner. Since the MJF pole
moves a lot with wind, I used the usual pulley and weight scheme to tension
the horizontal run of feedline. I needed to experiment with the feedline
length a bit to get a good match on all bands from 30 to 10 meters, but it
all worked out fine.
This has proved to be a great low angle antenna, better than the 20 meter GP
vertical with 12 radials I had previously, perhaps because the feed point is
elevated above the surrounding shrubbery and fencing. However, it isn't
exactly stealthy since at 33' in height it towers above the one-story house
and can be seen from quite a distance.
Also, I had to cement the first three joints (from the bottom) in the MJF
pole with Black Max adhesive since the lowermost sections tended to unlock
and collapse together somewhat when it got really windy.
Bob NW8L
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Rob Atkinson, K5UJ
Sent: Monday, July 11, 2005 5:42 PM
To: tentec@contesting.com
Subject: [TenTec] vertical dipoles
Anyone interested in more information about vertical dipoles should take a
look at what Cebik has to say. As always, he has excellent information that
is accurate and to the point:
http://www.cebik.com/gp/v20.html
rob/k5uj
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