144 MHz Omnidirectional Horizontal Antennas - Part
5
NEC Model Comparisons of Single Turnstile and Cebik
Triangle and Wheel Omnidirectional Horizontally
Polarized Antennas at 1.0λ for 144 MHz
by Dr. Carol F. Milazzo, KP4MD (posted 05 January 2013)
E-mail: [email protected]
INTRODUCTION
Among horizontally polarized antennas used for weak
signal VHF terrestrial communications, Cebik4
analyzed the Big Wheel, an omnidirectional array of
three full wave loops, as a 1.5λ circular radiator fed
at high impedance points through three radial spoke
parallel transmission lines. He proposed as an
alternative design an array of three discrete dipoles
fed at their low impedance points, either in an
equilateral triangle or curved into a circle.
This study uses NEC modeling to compare the expected
performance of each of these antenna designs against a
turnstile antenna. All antennas were modeled with 4nec2
at 1.0λ above a simulated ground.
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- Single
Halo,
Turnstile and Eggbeater at 0.5λ NEC Models
- Single
Halo,
Turnstile and Eggbeater at 1.0λ NEC Models
- Stacked
Halo,
Turnstile and Eggbeater Antenna NEC Models
- Single
Turnstile,
Triangle and Wheel at 0.5λ NEC Models
- Single
Turnstile,
Triangle and Wheel at 1.0λ NEC Models
- Stacked
Turnstile,
Triangle and Wheel Antenna NEC Models
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1. 144 MHz single Turnstile Antenna at 1λ horizontal
polarization radiation pattern calculated by NEC Model.
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2. 144 MHz single Cebik Triangle Antenna at 1.0λ
horizontal polarization radiation pattern calculated by
NEC Model.
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3. 144 MHz single Cebik Wheel Antenna at 1.0λ
horizontal polarization radiation pattern calculated by
NEC Model.
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4. 144 MHz single Turnstile Antenna at 1λ vertical
polarization radiation pattern calculated by NEC Model.
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5. 144 MHz single Cebik Triangle Antenna at 1.0λ
vertical polarization radiation pattern calculated by
NEC Model.
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6. 144 MHz single Cebik Wheel Antenna at 1.0λ vertical
polarization radiation pattern calculated by NEC Model.
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7. 144 MHz single Turnstile Antenna at 1λ azimuth
pattern calculated by NEC Model.
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8. 144 MHz single Cebik Triangle Antenna at 1.0λ
azimuth pattern calculated by NEC Model.
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9. 144 MHz single Cebik Wheel Antenna at 1.0λ azimuth
pattern calculated by NEC Model.
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10. 144 MHz single Turnstile Antenna at 1λ elevation
pattern calculated by NEC Model.
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11. 144 MHz single Cebik Triangle Antenna at 1.0λ
elevation pattern calculated by NEC Model.
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12. 144 MHz single Cebik Wheel Antenna at 1.0λ
elevation pattern calculated by NEC Model.
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13. 144 MHz single Turnstile Antenna at 1λ 4nec2
Calculations.
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14. 144 MHz single Cebik Triangle Antenna at 1.0λ 4nec2
Calculations.
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15. 144 MHz single Cebik Wheel Antenna at 1.0λ 4nec2
Calculations.
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CM 144 MHz Single Turnstile Antenna at 1.0
lambda NEC model by Carol F. Milazzo, KP4MD
CM Horizontal orientation
CM Frequency = 145.000 MHz
CM 21 segments per dipole
CM Simulated good ground
CM http://www.qsl.net/kp4md/omnihoriz.htm
CE
SY frq=145 'Input frequency MHz
SY len=39.815 'Input dipole length
inches
SY dia=0.25 'Input dipole dia.
inches
SY rad=0.5*dia 'Calculate dipole
radius
SY n=21 'Input segments per dipole
(must be odd)
SY nc=0.5*(n+1) 'Calculate feed
point segment
SY h=40.87 'Input height inches to
0.5 lambda
SY s=0.25 'Input separation
between each dipole in pair inches
GW 1
n 0
-len/2 h*2
0 len/2
h*2 rad
'First dipole at 1.0 lambda
GM 1
1 0
0 90
0 0
s 1
'Rotate to form second dipole at right angle
GS 0
0 0.0254
GE 1
LD 5
0 0
0 58000000
'0.25 inch copper tubing
GN 2
0 0
0 4 0.01
EK
EX 0
1 nc
0 0
1 0 'Feed
point
EX 0
2 nc
0 -1
0 0 'Feed
point
FR 0
0 0
0 frq 0
RP 0
1 361
1000 76.
0. 0.
1. 0.
EN
16. 144 MHz single Turnstile Antenna at 1.0λ NEC
model.
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CM 144 MHz Single Cebik Triangle Dipole
Antenna at 1.0 lambda NEC model by Carol F. Milazzo,
KP4MD
CM Horizontal orientation
CM Frequency = 145.000 MHz
CM 21 segments per dipole
CM Simulated good ground
CM http://www.qsl.net/kp4md/omnihoriz.htm
CE
SY frq=145 'Input frequency MHz
SY len=34.54444 'Input dipole
length inches
SY dia=0.5 'Input dipole wire dia.
inches
SY rad=0.5*dia 'Calculate dipole
wire radius
SY n=21 'Input segments per dipole
(must be odd)
SY nc=0.5*(n+1) 'Calculate feed
point segment
SY r=15.09081 'Input feedpoint to
hub distance inches
SY h=40.87 'Input height inches to
0.5 lambda
GW 1
n r
-len/2 h*2
r len/2
h*2 rad 'First
dipole at 1.0 lambda
GM 1
2 0
0 120
0 0
0 1 'Complete
the triangle
GS 0
0 0.0254
GE 1
LD 5
0 0
0 58000000 '0.5
inch copper tubing
GN 2
0 0
0 4 0.01
EK
EX 0
1 nc
0 1
0 0 'Feed point
EX 0
2 nc
0 1
0 0 'Feed point
EX 0
3 nc
0 1
0 0 'Feed point
FR 0
0 0
0 frq 0
RP 0
1 361
1000 76.
0. 0.
1. 0.
EN
17. 144 MHz single Cebik Triangle Antenna at 1.0λ NEC
model.
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CM 144 MHz Single Cebik Wheel Antenna at
1.0 lambda NEC model by Carol F. Milazzo, KP4MD
CM Horizontal orientation (using GH command)
CM Frequency = 145.000 MHz
CM 29 segments per element
CM Simulated good ground
CM http://www.qsl.net/kp4md/omnihoriz.htm
CE
SY frq=145 'Input frequency MHz
SY len=31.55469 'Input element
length inches
SY dia=0.5 'Input element wire
dia. inches
SY rad=0.5*dia 'Calculate element
wire radius
SY n=29 'Input segments per
element (must be odd)
SY nc=0.5*(n+1) 'Calculate feed
point segment
SY cir=97.34283 'Input wheel
circumference inches
SY r=0.5*cir/3.1415926 'Calculate
wheel radius
SY h=40.87 'Input height inches to
0.5 lambda
GH 1
n 1e-300
1e-300*(len/cir)
r r
r r
rad 'First element
GM 1
2 0
0 120
0 0
0 0 'Complete
the wheel
GM 0
0 0
0 0
0 0
h*2 1 'Raise
antenna to 1.0 lambda
GS 0
0 0.0254
GE 1
LD 5
0 0
0 58000000 '0.5
inch copper tubing
GN 2
0 0
0 4 0.01
EK
EX 0
1 nc
0 1
0 0 'Feed point
EX 0
2 nc
0 1
0 0 'Feed point
EX 0
3 nc
0 1
0 0 'Feed point
FR 0
0 0
0 frq 0
EN
18. 144 MHz single Cebik Wheel Antenna at 1.0λ NEC
model.
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RESULTS
- All antennas had maximum lobe gains between 4.1 and
6.1 dBi at 15º elevation.
- The Cebik Triangle and Wheel antennas more closely
approximated an omnidirectional pattern with 0.1-0.2
dB variation in azimuth radiation while the turnstile
antenna exhibited a 1.0 dB differential in gain.
- The Cebik Triangle and Wheel antennas showed deep
nulls in their radiation patterns toward the zenith
while the turnstile antenna had a -1 dBi minor lobe in
that direction.
- The turnstile antenna exhibited the
least suppression of vertically polarized noise.
CONCLUSION
Although the overall expected performance of each of
the models is similar, the following factors should be
considered:
- The difference in performance may not warrant
incurring the greater construction complexity of any
particular antenna design.
- The losses incurred in the additional stacking and
phasing harnesses may diminish or negate the expected
gain in any particular antenna design.
- Deviations in the antenna and phasing harness
dimensions can significantly skew the radiation
patterns.3
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19. Composite of all 144 MHz Antennas at 1.0λ azimuth
patterns - horizontal polarization component only.
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20. Composite of all 144 MHz Antennas at 1.0λ azimuth
patterns - vertical polarization component only.
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REFERENCES
- The
HO Collinear, A Horizontal Omni, Anderson R,
W1HBQ
- The
Double Turnstile Antenna, Beech J, G8SEQ
- Horizontally
Polarized Omni-Directional Antennas: Some Compact
Choices, Part 1, Cebik, LB, W4RNL
- Horizontally
Polarized Omni-Directional Antennas: Some Compact
Choices, Part 2, Cebik, LB, W4RNL
- Experimental
Omnidirectional Antennas for 6-Meters, Cebik,
LB, W4RNL
- 144 MHz Halo Antenna,
Milazzo C, KP4MD
APPENDIX: NEC MODEL FILES
- 144 MHz Single
Turnstile Antenna at 1.0λ NEC Model
- 144 MHz Single
Triangle Antenna at 1.0λ NEC Model
- 144
MHz Single Wheel Antenna at 1.0λ NEC Model
LINKS
- Single Halo,
Turnstile and Eggbeater at 0.5λ NEC Models
- Single
Halo, Turnstile and Eggbeater at 1.0λ NEC Models
- Stacked
Halo, Turnstile and Eggbeater Antenna NEC Models
- Single
Turnstile, Triangle and Wheel at 0.5λ NEC Models
- Single
Turnstile, Triangle and Wheel at 1.0λ NEC Models
- Stacked
Turnstile, Triangle and Wheel Antenna NEC Models
- Omnidirectional
Horizontal
Antenna Photo Album
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21. Composite of all 144 MHz Antennas at 1.0λ elevation
patterns - horizontal polarization component only.
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22. Composite of all 144 MHz Antennas at 1.0λ elevation
patterns - vertical polarization component only.
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