[TowerTalk] modeling a v shaped dipole

[Gary Slagel]

I didn't do a very good job of describing the antenna.  I'm not really folding the ends back into a C.   I'm making a flat V.... like an inverted Vee but with the ends horizontal rather then drooping to the ground.  
 
I didn't expect much effect as I brought them back to enclose a 135 degree Vee but I was surprised that when the Vee was enclosing only a 45 degree angle, EZNEC still showed it with an identical pattern to a broadside dipole.   So... if the pictures I drew below are understandable, I wouldn't have thought these two dipoles would have an identical azimuthal pattern!
 
----------------o o---------------- broadside dipole viewed from above
 
                o o               45 degree vee dipole viewed from above
              /      \
            /          \
          /              \


From: jimlux <jimlux at earthlink.net>
Subject: Re: [TowerTalk] modeling a v shaped dipole
To: "Gary Slagel" <gdslagel at yahoo.com>
Cc: "TowerTalk" <towertalk at contesting.com>
Date: Friday, September 25, 2009, 7:27 AM


Gary Slagel wrote:
> Hi guys,
> 
> I tried to model a v shaped dipole yesterday and was surprised by the
> results.  I'm looking at a dipole with the ends bent back toward each
> other rather then an inverted vee.  I started with a straight dipole,
> then bent the ends toward each other so they enclosed a 135 degree
> angle, then bent them to enclose a 90 degree angle, and last a 45
> degree angle.
> 
> The azimuth pattern I got was identical for each configuration.  The
> direction was different depending on how I rotated the wire to change
> the angle, but the pattern was identical.
> 
> Does this seem reasonable or was I making an error or does eznec have
> a problem modeling this?  I was using the free eznec provided with
> the arrl antenna book.
> 
> 

the entire antenna is all in a flat plane? so it's looking sort of like a big "C"

Most of the pattern is determined by the middle of the dipole, so bending the ends doesn't do much other than change the feedpoint impedance. a half length (1/4 wavelength long overall) dipole with capacity hats to make it resonant has almost exactly the same pattern as a full sized dipole.

In fact, an idealized dipole has about 2.2 dBi gain, while an infintesimally small dipole (called a Hertzian dipole) has a gain of about 1.7 dBi.. unless you plot the two patterns on top of each other, you wouldn't notice the difference.