July 9th 12, 02:38 AM
posted to rec.radio.amateur.antenna
|
|
external usenet poster
|
|
First recorded activity by RadioBanter: Jun 2006
Posts: 1,898
|
|
Dipole-2 different wire sizes?
John H. Guillory wrote:
On Sun, 8 Jul 2012 17:19:51 -0000, wrote:
[- You should know that the true dipole is directional.
[- Are your "dipoles" directional?
[-
[-Dipoles are not directional, they are bidirectional in the plane of
the
[-antenna and ALL dipoles are bidirectional in the plane of the
antenna.
Just a FYI to jump in over here.... According to the General
Class Amateur License Exam, a Dipole has figure 8 resonance off both
ends of the dipole at 90 degrees from the poles. If, however, the
dipole is lowered below 1/2 the wave length, the dipole becomes
omni-directional. Just thought I'd throw that in.... The exact
wording may be a little different, but.... Just wanted to toss that
into the flames and ignite it a little more...
KF5QEO
Well, the height over ground will effect the pattern, but it does not
become omnidirectional.
As you get lower in height, the null of a free space or high antenna
starts going away.
At wavelengths over ground:
2, ends are 30 db down from broadside
1, about 22 db down
..5, about 10 db down
..25, about 3 db down
So it approaches omnidirectonal as you get lower but is only omnidirectional
at zero height.
EZNEC is your friend.
|