Was the year 1958 or 2008? Did he build the dipole or the vertical? Did he
know what he was doing? Etc.
"Just so" stories can mean anything or nothing. I have a vertical and a low
dipole in a valley. Each has good days, each has bad days. Both could be
improved (and will be!). I've made contacts near my antipode on both, but
not this year.
Rich
NU6T
-----Original Message-----
From: Dennis OConnor [mailto:ad4hk2004@yahoo.com]
Sent: Thursday, December 11, 2008 6:59 AM
To: towertalk@contesting.com
Subject: [TowerTalk] vertical antenna ground loss
The word picture (and diagrams) of the 'missing half 'of a dipole antenna
going down into the ground is a device to help visualization of how the
induced ground currents act to complete the return current flow for a
quarter wave monopole (vertical)... It is not what is actually happening in
the generated EM field underneath the vertical... I can assure you that a
160 meter quarter wave monopole does not have an image 130 feet down into
the dirt and rocks,...
An elevated ground plane antenna also has radials just like a ground mounted
vertical yet we do not see authors repeatedly claiming that there is an
image of half a dipole forming below the radials - though some do, must be
what they are smoking...
Next, the 'poor performance' of vertical antennas is grounded in the lack of
knowledge of those making such claims...
Lets us discuss two antennas for 40 meters... A half wave DIPOLE hung
horizontally a quarter wave above ground - and a quarter wave MONOPOLE
(vertical), ground mounted...
Now, the dipole has that wonderful 4dB of reflection gain (or whatever your
favorite fantasy dB number is) giving is something in the 6dBi range......
And the poor, tired vertical has a ground loss of xxx dB (pick your favorite
fantasy dB number) and no reflection gain so it is struggling along at 1.25
dBi (or some such - you pick it)...
So now, Joe Ham wants to talk to his friend Bob, 175 miles away.... On the
dipole Joe is booming in at Bob's qth, and on the vertical Bob can
barely hear him... Yup, it just proves that verticals radiate equally poorly
on all directions...
Later that day Joe hears a DX station on a tiny rock in the middle of that
antarctic ocean exactly half way around the world from his shack (the
antipode)...
He calls on the dipole... The DX goes CQ back in his face... He calls and
calls and calls... No joy... Finally, in frustration and about to give up he
switches to the inferior, radiates equally poorly in all
directions, vertical - and gets an answer on his first call...
So, which antenna is inferior?
denny / k8do
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