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[TowerTalk] Shortened Dipole on 160M

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Subject: [TowerTalk] Shortened Dipole on 160M
From: (David L. Thompson)
Date: Wed, 19 Sep 2001 15:08:23 -0400
I have used several shortened dipoles on 160.  In the late 80's I had a Van
Gorden dipole that was 135 feet long with loading out each leg
toward the ends.   I found that it worked best with one leg vertical and one
leg horizontal with the vertical leg about 15 feet off the ground.
It worked well but only covered about 20Khz without need for a tuner.   I
gave this one to PA3CXC to put rare African locations on 160 (he made 120
Q's from PA3CXC/ST0).

A spi-ro dipole (only 100 feet long) was used at 4U1UN for the world high
M/O score in the 1993 CQ 160 CW.   The gang tried a vertical with 160
loading but settled on the spi-ro.  The antenna was mounted 20 feet above
the  70 story UN building in NYC.   The antenna worked well enough so that I
have picked up several sets of the Spi-ro loading coils directly or at
hamfests to make 50 foot radials.
My L and later Multee had 6 of them in an elevated ground plane.  I have not
tried to lay them on the ground although Gladiator verticals used loaded
radials laid on the ground for their 160 and 80 verticals.  BTW KR1G used
the 160 Gladiator (38 feet tall)  for a nice score in the CQ 160 CW.

I now have another 135 foot loaded dipole that I will try either inverted V
fashion NE/SW with the center at 70' or perhaps in K8UR vertical
fashion.   This antenna is tuned to 1849 and has about 45 khz of low SWR
before the tuner is needed and the tuner can be preset with one position for
low band (1815) and high band (1880) for contest use.  Don't know what
effect the vertical position will have but usually the swr range stays the
same just moves up the band 10 or 15 Khz.  Guess its because the top goes
from 70' to 98'.

The efficiency of a loaded dipole (if care is taken to build high Q coils)
is very near a full size dipole.  The only compromise you face is having a
narrow SWR range.  Use of a tuner eliminates this problem but makes broad
band operation more complex.

I always try to have 2 or more 160 antennas up as a vertical is best for Dx
but an inverted V is best for short skip.

73 Dave K4JRB

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