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[email protected] · April 3rd 14, 05:29 PM posted to rec.radio.amateur.antenna

Wimpie wrote:
El 03-04-14 1:04, escribió:
Ian wrote:
In ,
writes

The theoretical gain of a GP with horizontal radials, radials drooping
45 degrees and and drooping 85 degrees is 1.42, 2.22, and 3.67 dbi.

I would have thought that the 'ultimate' would be when the droop IS 90
degrees (ie essentially a sleeve dipole).

With a droop of 90 degrees, is the gain slightly more than 3.67?

You can't physically have a 90 degree droop. The radials would have to
extend horizontally for some distance, then drop to 90 degrees.

This is the same as saying, you can't have a 90 degree radiator, as
due to wind it will bend. You know that going horizontally a few inch
and then 90 degrees down doesn't make big difference compared to 85
degrees sloping. You only may experience some length difference to get
lowest common mode current in the mast or feeder. Both option will not
give you more gain compared to a half wave dipole (free space).

If you do this you do not have a ground plane antenna; you have an asymmetric
dipole with one skinny element and one fat element.

That is a different antenna.

How come that you can have a 1/4 wave radiator groundplane type of
antenna with a gain that is more than a halfwave dipole (2.15 dBi) -even
if it is more-or-less a sleeve dipole?

When the radial droop approaches 90 degrees it really isn't a GP antenna
anymore, it is something else.

Is this because of electrical operation (I doubt), or naming convention?

Actually both.

BTW, in retrospect I don't think that 3.67 dbi number for 85 degrees is
correct.

The limiting gain should be that of a vertical dipole as you pointed out.

I think the problem is that most analysis programs have issues with very
close wires and very small angles.

This can be seen by analyzing a fan dipole and decreasing the angle between
the elements. Eventually the results stop making any sense.

--
Jim Pennino