RadioBanter - View Single Post

Cecil Moore · July 11th 06, 04:04 PM posted to rec.radio.amateur.antenna

wrote:
Cecil Moore wrote:
A free space vertical with horizontal radials in EZNEC
has horizontal radiation more than 40 dB down from the
vertical radiation. That's a high degree of cancellation.

The issue is the horizontal opposing radials only have that degree of
cancellation for perfectly horizontal directions.

That's the issue? Something that no one has ever asserted
otherwise?

You will be able to see your statement isn't true if you place the
antenna in freespace and look at pattern distortion at various
elevation angles. For example, the 2-d plot is skewed 2.11 dB from
being circular at - 45 and +45 degrees elevation. The skewing gets
worse at larger angles from the plane of the radials.

Just ran that test. There was 0.02 dB difference at +45 and -45.

If the radials were REALLY radiating -40dB in all directions as you
wrongly assume, there would NOT be significant FS change in the azimuth
pattern at various elevations.

There is no significant FS change according to EZNEC.

You looked at horizontal radiation, but the horizontal radials peak
radiation is vertically polarized and nearly off the radial's ends.
(Just like in a dipole pattern.)

Unfortunately for that argument, the radiating currents in
a dipole are in phase, i.e. designed for maximum radiation. The
radiating currents in symmetrical radials are 180 degrees
out of phase, i.e. designed for minimum radiation.
--
73, Cecil http://www.qsl.net/w5dxp