Dennis,
EZNEC modelling certainly doesn't confirm what you are saying.
I just modelled a 40m horizontal half-wave 33ft above average ground -
the optimum take-off angle was 66 degrees. Then I modelled a
quarter-wave vertical over 16 quarter-wave ground mounted radials - the
optimum take-off angle was 26 degrees. But, plot these on a common scale
and you'll see there's hardly any difference at low take-off angles:
http://www.karinya.net/g3txq/vert_vs_dipole.png
From 20 degrees upwards the dipole beats the vertical, which would
confirm your "short skip" comment; but what in these figures suggests
the vertical will be so much superior for DX ?
Steve G3TXQ
Dennis OConnor wrote:
> 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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