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John S · October 12th 14, 04:20 PM posted to rec.radio.amateur.antenna

On 10/12/2014 12:41 AM, wrote:
Jeff Liebermann wrote:
On Sat, 11 Oct 2014 18:04:07 -0000, wrote:

Jeff Liebermann wrote:

snip

Speaking of dipole antennas, I did this study a while back:
http://802.11junk.com/jeffl/antennas/vertical-dipole/index.html
Animated version:
http://802.11junk.com/jeffl/antennas/vertical-dipole/slides/animated-v-dipole.html
It's a 1/2 wave dipole at various heights above a real ground. Any
semblance to textbook dipole pattern is long gone.

Yep, ground has a huge effect on some types of antennas.

An instructive slide show would be the vertical pattern of a horizontal
1/2 dipole at .1, .2, ... .5 wavelengths over ground.

Another one would be a 3 element beam at those heights.

I can do both of these, but I'm busy/lazy this weekend. I also can't
find the program I used to create the annimated GIF file. Argh. It
would also be helpful if someone would specify the frequency range of
interest.

It doesn't matter if everything is done in wavelengths.

I guess there are some who would want to see that a 160 meter dipole
at say .2 wavelengths high has the same pattern as a 2 meter dipole
at .2 wavelengths if for no other reason than to be assured the effects
are frequency independant.

Something else might be interesting; include the effects of sag
(centenary) in a wire antenna. Has anyone done that? I mean, using EZNEC
or NEC modeling.

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