[TowerTalk] Inverted Vees

[jimlux]

On 6/15/20 11:53 PM, Jim Thomson wrote:
> Date: Mon, 15 Jun 2020 14:35:40 -0700
> From: jimlux <jimlux at earthlink.net>
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Inverted Vees
> 
> <for an idealized half wave dipole, the 10dB down point is at about 67
> <degrees off broadside.
> <For a 1/4 wavelength (half length) dipole, it's at about 70.5 degrees,
> <and for an infinitesimal dipole it's at 71.5 degrees
> 
> <For 20 dB it's 82.7, 84, and 84.3.
> 
> 
> <That is, if you are 23 degrees off the end, your "depth of null" is
> <10dB. To be 20 dB down, you've got to be about +/- 7 degrees.
> 
> <The null is sharper for the smaller antenna, which seems somewhat
> <counter intuitive.
> 
> ##  What is the null depth  when its  exactly at  90 degs ??  IE:  directly off the ends of the  dipole.
> 
>

These are theoretical dipoles, so infinite null.


for those interested, here's the equation

"""
returns power gain (linear, not dB)
theta is angle from broadside
kL is length of dipole - default (pi) is half wavelength

Hertzian dipole (kL=0) handled as special case to avoid divide by zero 
in general formula
"""

def dipolegain(theta,kL=np.pi):
     tt = np.pi/2.0 - theta
     if kL==0:
         return(np.sin(tt)**2)
     if tt == 0:
         return(0)
     else:
         return ((np.cos(kL/2.*np.cos(tt))-np.cos(kL/2.))/np.sin(tt))**2