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Topband: 5/8 wavelength vertical is mo betta than shorter versions??

To: "topband@contesting.com" <topband@contesting.com>
Subject: Topband: 5/8 wavelength vertical is mo betta than shorter versions??
From: James Rodenkirch <rodenkirch_llc@msn.com>
Date: Sat, 7 Sep 2013 17:24:45 -0600
List-post: <topband@contesting.com">mailto:topband@contesting.com>


I saw someone post a "my 5/8 wavelength vertical really outperformed my 1/4 
wavelength vertical" a day or two ago.
I kinda wondered about that (I've "heard" a 5/8 wavelength is mo betta) so I 
did a little digging around.
From a K3LC paper on tall verticals - 
http://www.arrl.org/files/file/QEX_Next_Issue/May-Jun_2011/QEX_5_11_Christman.pdf
 - I found the below:

Performance comparison between vertical antenna systems of varying height, when 
operating on 80 meters at a frequency of 3650 kHz. The monopoles are made from 
no. 10 AWG wire, with a ground screen composed of 60 buried no. 14 AWG radials 
(radial length = monopole height). All conductors are aluminum, and the soil is 
“average” (conductivity = 0.005 siemens/meter and dielectric constant = 13).
¼ λ System                               3⁄8 λ System                  ½ λ 
System                   5⁄8 λ SystemMonopole Height and Radial Length (ft) 
67.368                                      101.05                            
134.74                            168.42Input Impedance (Ω) 41.4 + j 24.4       
                       229 + j 605                     2324 – j 1425            
       86.1 – j 479SWR (50 Ω ref.) 1.75                                         
 36.8                               64.0                                 
55.5Peak Gain (dBi) and Take-off Angle (°)0.39 at 24.7                          
     0.79 at 21.7                    0.96 at 17.6                      0.42 at 
13.3Gain (dBi) at 5° Take-off Angle–5.21                                       
–4.34                              –3.42                                
–2.81Gain (dBi) at 10° Take-off Angle –1.70                                     
  –0.91                              –0.14                                
0.06Gain (dBi) at 15° Take-off Angle –0.32                                      
 0.35                                0.85                                 
0.34Gain (dBi) at 20o Take-off Angle 0.25                                       
 0.76                                 0.89                                
–0.63Half Power Beamwidth (°) 43.7                                        38.0  
                               29.0                                 
20.3Efficiency (%) 33.8                                        34.3             
                    29.6                                 29.8

Performance comparison between vertical antenna systems of varying height, when 
operating on 40 meters at a frequency of 7150 kHz.
The monopoles are made from no. 10 AWG wire, with a ground screen composed of 
60 buried no. 14 AWG radials (radial length =monopole height). All conductors 
are aluminum, and the soil is “average” (conductivity = 0.005 siemens/meter and 
dielectric constant = 13).
¼ λ System                   3⁄8 λ System                                       
½ λ System                                    5⁄8 λ SystemMonopole Height and 
Radial Length (ft) 34.391                           51.586                      
                           68.781                                               
 85.976Input Impedance (Ω) 39.9 + j 25.0                   235 + j 570          
                              1937 – j 1247                                     
  81.9 – j 436SWR (50 Ω ref.) 1.81                                32.5          
                                          54.8                                  
                 48.7Peak Gain (dBi) and Take-off Angle (°) 0.15 at 26.2        
             0.68 at 23.3                                        0.89 at 19.1   
                                      0.68 at 14.5Gain (dBi) at 5° Take-off 
Angle–6.15                              –5.15                                   
               –4.13                                                  –3.12Gain 
(dBi) at 10° Take-off Angle –2.38                              –1.44            
                                      –0.56                                     
             0.08Gain (dBi) at 15° Take-off Angle –0.82                         
      0.02                                                     0.66             
                                     0.67Gain (dBi) at 20° Take-off Angle –0.11 
                              0.59                                              
       0.88                                                  0.04Half Power 
Beamwidth (°) 44.1                                 39.3                         
                            30.7                                                
  22.3Efficiency (%) 31.9                                 34.0                  
                                   30.4                                         
         31.7
Performance comparison between vertical antenna systems of varying height, when 
operating on 20 meters at a frequency of14.175 MHz. The monopoles are made from 
no. 10 AWG wire, with a ground screen composed of 60 buried no. 14 AWG radials 
(radial length = monopole height). All conductors are aluminum, and the soil is 
“average” (conductivity = 0.005 siemens/meter and dielectric constant = 13).
¼ λ System                       3⁄8 λ System                            ½ λ 
System                      5⁄8 λ SystemMonopole Height and Radial Length (ft) 
17.347                               26.020                                     
 34.694                              43.367Input Impedance (Ω) 39.0 + j28.4     
                  247 + j536                                 1595 – j1070       
               77.4 – j392SWR (50 Ω ref.) 1.97                                  
28.3                                           46.3                             
    41.8Peak Gain (dBi) and Take-off Angle (°) 0.29 at 27.1                     
  0.91 at 24.3                                1.16 at 19.9                      
1.21 at 15.0Gain (dBi) at 5° Take-off Angle –6.35                               
 –5.28                                          –4.18                           
     –2.86Gain (dBi) at 10° Take-off Angle –2.46                                
–1.45                                          –0.49                            
    0.48Gain (dBi) at 15° Take-off Angle –0.8                                 1 
0.1                                           1 0.84                            
   1.21Gain (dBi) at 20° Take-off Angle –0.04                               
0.76                                             1.16                           
       0.70Half Power Beamwidth (°) 44.4                                 40.4   
                                          31.5                                  
22.8Efficiency (%) 32.9                                 36.3                    
                          32.9                                 34.7
The above modeling results just don't support that contention/posit so I'm 
wondering what else comes in to play that could lead folks to love the 5/8 
wavelength vertical over a shorter version, regardless of frequency?  I don't 
see one performance comparison that supports that claim.  I'm not saying the 
"claiming person" isn't correct but....I don't see how!
Help - what am I missing here?
72, Jim Rodenkirch K9JWV
                                          
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