Agreed with all of that. I don't think were talking anywhere near 50'
certainly not 100'. 30' maybe. It's a rooftop tower.
At 100' EZNEC says the 40m dipole kicks butt, 50 feet not so much and
30 feet even less.
On 4/29/2016 4:59 AM, Jim Thomson wrote:
Date: Thu, 28 Apr 2016 18:54:17 -0500
From: Kevin Stover <kevin.stover@mediacombb.net>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Looking for a Short Rotatable Dipole or...
K9YC has given the best advice.
A dipole, any dipole at less than 1/2 wavelength isn't going to have any
lobes to rotate so scratch the dipole idea. It'll be pretty much
omnidirectional.
R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441
## tell that to the folks with 80m rotary dipoles up 100’.....
or folks with 40m rotary dipoles up 50’. That null off the
ends is nothing to sneeze at. 6-14 db, depending on whether its local or
dx. Some will use 2 x wire dipoles at 90 deg apart..... but they are
configured more like a T, when looking down on the pair of dipoles.
And try and get the center of one dipole,away from the end of the 2nd dipole.
Dont cross them in the middle like an X. But that mess requires 4 x supports
## Inverted vee. Now they are omnidirectional. Even a vee with a 90 deg
angle
between legs will radiate off the sides...and off the ends.
## Put the apex of the vee at the same height as the dipole, and the dipole
will be 6 db stronger off its sides. Dipole also has the nulls off the ends.
## Inverted vee is good, a dipole is better, and a rotary dipole is better
still,
or 2 x crossed dipoles. 6-14 db null off the ends might not sound like much,
until the station you are trying to work is in the null.
## I have tried 40m GPs, with the very top at 70 feet, and they worked good,
as did the 40m GPs, with the very top at 56 feet. Both had loads of elevated
radials.
Surprisingly enough, neither config had an issue with noise, they were fairly
quiet.
Only issue with a GP is.... with no nulls obviously, you hear everything, from
every direction.
## any shorty 40m, 2 el yagi, even as low as 60 ft, will make lunchmeat out
of any vertical array,
even a ground mounted 4 square.
Jim VE7RF
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R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441
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