144 MHz Omnidirectional Horizontal Antennas - Part
6
NEC Model Comparisons of Stacked Turnstile and
Cebik Triangle and Wheel Omnidirectional Horizontally
Polarized Antennas 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. The antennas were modeled with
4nec2 at 0.5λ and 1λ 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 stacked Turnstile Antenna horizontal
polarization radiation pattern calculated by NEC Model.
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2. 144 MHz stacked Cebik Triangle Antenna horizontal
polarization radiation pattern calculated by NEC Model.
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3. 144 MHz stacked Cebik Wheel Antenna horizontal
polarization radiation pattern calculated by NEC Model.
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4. 144 MHz stacked Turnstile Antenna vertical
polarization radiation pattern calculated by NEC Model.
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5. 144 MHz stacked Cebik Triangle Antenna vertical
polarization radiation pattern calculated by NEC Model.
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6. 144 MHz stacked Cebik Wheel Antenna vertical
polarization radiation pattern calculated by NEC Model.
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7. 144 MHz stacked Turnstile Antenna azimuth pattern
calculated by NEC Model.
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8. 144 MHz stacked Cebik Triangle Antenna azimuth
pattern calculated by NEC Model.
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9. 144 MHz stacked Cebik Wheel Antenna azimuth pattern
calculated by NEC Model.
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10. 144 MHz stacked Turnstile Antenna elevation pattern
calculated by NEC Model.
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11. 144 MHz stacked Cebik Triangle Antenna elevation
pattern calculated by NEC Model.
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12. 144 MHz stacked Cebik Wheel Antenna elevation
pattern calculated by NEC Model.
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14. 144 MHz stacked Turnstile Antenna 4nec2
Calculations.
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14. 144 MHz stacked Cebik Triangle Antenna 4nec2
Calculations.
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15. 144 MHz stacked Cebik Wheel Antenna 4nec2
Calculations.
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CM 144 MHz Stacked Turnstile Antenna 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
0 len/2
h rad 'First
dipole at 0.5 lambda
GM 1
1 0
0 90
0 0
s 1 'Rotate to
form second dipole at right angle
GM 2
1 0
0 0
0 0
h 1 'Copy dipole
pair to 1.0 lambda
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
EX 0
3 nc
0 0
1 0 'Feed point
EX 0
4 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 stacked Turnstile Antenna NEC model.
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CM 144 MHz Stacked Cebik Triangle Dipole
Antenna 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
r len/2
h rad 'First
dipole at 0.5 lambda
GM 1
2 0
0 120
0 0
0 1 'Complete
the triangle
GM 3
1 0
0 0
0 0
h 1 'Copy
triangle to 1 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
EX 0
4 nc
0 1
0 0 'Feed point
EX 0
5 nc
0 1
0 0 'Feed point
EX 0
6 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 stacked Cebik Triangle Antenna NEC model.
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CM 144 MHz Stacked Cebik Wheel Antenna 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 1 'Raise
antenna to 0.5 lambda
GM 3
1 0
0 0
0 0
h 1 'Copy wheel
to 1 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
EX 0
4 nc
0 1
0 0 'Feed point
EX 0
5 nc
0 1
0 0 'Feed point
EX 0
6 nc
0 1
0 0 'Feed point
FR 0
0 0
0 frq 0
EN
18. 144 MHz stacked Cebik Wheel Antenna NEC model.
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RESULTS
- All antennas had maximum lobe gains between 6.8 and
7.1 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 dB differential in gain.
- All antennas had nulls exceeding -30 dBi toward the
zenith, most pronounced in the Cebik Triangle and
Wheel antennas.
- 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 azimuth patterns
- horizontal polarization component only.
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20. Composite of all 144 MHz Antennas 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
Stacked Turnstile Antenna NEC Model
- 144 MHz Stacked
Triangle Antenna NEC Model
- 144
MHz Stacked Wheel Antenna 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 elevation
patterns - horizontal polarization component only.
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22. Composite of all 144 MHz Antennas elevation
patterns - vertical polarization component only.
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