Topband: 5/8 wavelength vertical is mo betta than shorter versions??
Charlie Cunningham
charlie-cunningham at nc.rr.com
Sat Sep 7 20:21:38 EDT 2013
BTW, Jim
Nothing wrong with a 1/4 wave ground-plane! I've done really well on 40, 80 and 160 with quarter-wave verticals ( if you're willing to accept the 160 inverted L as a "quarter wave vertical".) I am - the models say it has comparable gain and radiation patterns. ( also ran elevated resonant radials under the 160 inv L.
Also, for a while I had both a vertical dipole and a 1/4 wave GP here for 40m. The GP was very competitive with the 1/2 wave 40m vertical diple on long-paths into Asia. ( I could switch back and forth between the two antennas. The GP wasn't very high - abt 12'.
My 80m GP with 3 elevated resonant radials is an excellent WW DX antenna, but it's also a really good DX antenna on 30m, where it's approaching 270 degrees in length, or 3/4 wavelength. The EZNEC model show that it has a fairly high angle radiation pattern - approaching 45 degrees elevation, but its gain is a little over 6dBi on 30m, so even at lower angles it's a pretty decent radiator. Hears pretty well too, on 30m, but not as good as te KAZ loop in directions away from the null in the KAZ loop's cardioid pattern.
73,
Charlie, K4OTV
-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of James Rodenkirch
Sent: Saturday, September 07, 2013 7:25 PM
To: topband at contesting.com
Subject: Topband: 5/8 wavelength vertical is mo betta than shorter versions??
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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