On 6/15/20 11:53 PM, Jim Thomson wrote:
Date: Mon, 15 Jun 2020 14:35:40 -0700
From: jimlux <jimlux@earthlink.net>
To: towertalk@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
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