144 MHz Omnidirectional Horizontal Antennas - Part 1

NEC Model Comparisons of Single Halo, Turnstile and Eggbeater Omnidirectional Horizontally Polarized Antennas at 0.5λ for 144 MHz

by Dr. Carol F. Milazzo, KP4MD (posted 05 January 2013)
E-mail: kp4md@arrl.net

INTRODUCTION

The halo (HO Loop), turnstile, eggbeater and Big Wheel are omnidirectional horizontally polarized antennas used for weak signal VHF terrestrial communications.  Cebik3 duly described the benefits and problems of each of these antenna designs.  These antennas can be stacked to increase gain at low elevation angles and to decrease sensitivity to noise from high elevation angles.

This study in six parts presents NEC models that compare the expected performance of these antennas.  Each antenna was modeled with 4nec2 singly at 0.5λ and at 1λ height and as a stacked pair at 0.5λ and 1λ above a simulated ground.  We used variables and the GH (helix) and GM (move) NEC commands to facilitate customization and the use of the optimizer function.

  1. Single Halo, Turnstile and Eggbeater at 0.5λ NEC Models
  2. Single Halo, Turnstile and Eggbeater at 1.0λ NEC Models
  3. Stacked Halo, Turnstile and Eggbeater Antenna NEC Models
  4. Single Turnstile, Triangle and Wheel at 0.5λ NEC Models
  5. Single Turnstile, Triangle and Wheel at 1.0λ NEC Models
  6. Stacked Turnstile, Triangle and Wheel Antenna NEC Models

144 MHz single Halo Antenna horizontal
                      polarization radiation pattern calculated by NEC
                      Model.

1. 144 MHz single Halo Antenna at 0.5λ horizontal polarization radiation pattern calculated by NEC Model.

144 MHz single Turnstile Antenna horizontal
                      polarization radiation pattern calculated by NEC
                      Model.

2. 144 MHz single Turnstile Antenna at 0.5λ horizontal polarization radiation pattern calculated by NEC Model.

144 MHz single Eggbeater Antenna horizontal
                      polarization radiation pattern calculated by NEC
                      Model.

3. 144 MHz single Eggbeater Antenna at 0.5λ horizontal polarization radiation pattern calculated by NEC Model.

144 MHz single Halo Antenna vertical
                      polarization radiation pattern calculated by NEC
                      Model.

4. 144 MHz single Halo Antenna at 0.5λ vertical polarization radiation pattern calculated by NEC Model.

144 MHz single Turnstile Antenna vertical
                      polarization radiation pattern calculated by NEC
                      Model.

5. 144 MHz single Turnstile Antenna at 0.5λ vertical polarization radiation pattern calculated by NEC Model.

144 MHz single Eggbeater Antenna vertical
                      polarization radiation pattern calculated by NEC
                      Model.

6. 144 MHz single Eggbeater Antenna at 0.5λ vertical polarization radiation pattern calculated by NEC Model.

144 MHz single Halo Antenna azimuth pattern
                      calculated by NEC Model.

7. 144 MHz single Halo Antenna at 0.5λ azimuth pattern calculated by NEC Model.

144 MHz single Turnstile Antenna azimuth
                      pattern calculatedby NEC Model.

8. 144 MHz single Turnstile Antenna at 0.5λ azimuth pattern calculated by NEC Model.

144 MHz single Eggbeater Antenna azimuth
                      pattern calculatedby NEC Model.

9. 144 MHz single Eggbeater Antenna at 0.5λ azimuth pattern calculated by NEC Model.

144 MHz single Halo Antenna elevation pattern
                      calculated by NEC Model.

10. 144 MHz single Halo Antenna at 0.5λ elevation pattern calculated by NEC Model.

144 MHz single Turnstile Antenna elevation
                      pattern calculatedby NEC Model.

11. 144 MHz single Turnstile Antenna at 0.5λ elevation pattern calculated by NEC Model.

144 MHz single Eggbeater Antenna elevation
                      pattern calculated by NEC Model.

12. 144 MHz single Eggbeater Antenna at 0.5λ elevation pattern calculated by NEC Model.

144MHz single Halo Antenna 4nec2Calculations.

13. 144 MHz single Halo Antenna at 0.5λ 4nec2 Calculations.

144MHz single Turnstile Antenna 4nec2
                    Calculations.

14. 144 MHz single Turnstile Antenna at 0.5λ 4nec2 Calculations.

144MHz single Eggbeater Antenna 4nec2
                    Calculations.

15. 144 MHz single Eggbeater Antenna at 0.5λ 4nec2 Calculations.

CM 144 MHz Single Halo Antenna at 0.5 lambda NEC model by Carol F. Milazzo, KP4MD
CM Horizontal orientation (using GH command)
CM Frequency = 145.000 MHz
CM 26-side polygon (40 inch loop with 1.5 inch gap)
CM Simulated good ground
CM http://www.qsl.net/kp4md/omnihoriz.htm
CE
SY frq=145    'Input frequency MHz
SY cir=40.21493    'Input loop circumference inches (loop + gap)
SY r=0.5*cir/3.1415926    'Calculate loop radius
SY dia=0.25    'Input loop wire dia. inches
SY rad=0.5*dia    'Calculate loop wire radius
SY n=26    'Input n-side polygon of loop + gap
SY h=40.87    'Input height inches to 0.5 lambda
SY g=1.5    'Input gap size in inches
SY gseg=int(n*g/cir+0.5)    'Calculate gap length in segments
GH    1    n-gseg    1e-300    1e-300*(n-gseg)/n    r    r    r    r    rad    'First loop
GM    0    0    0    0    gseg*180/n    0    0    h    1    'Raise loop to 0.5 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    (n-gseg)/2    0    0.5    0    0    'Feed point
FR    0    0    0    0    frq    0
EN

16. 144 MHz single Halo Antenna at 0.5λ NEC model.

CM 144 MHz Single Turnstile Antenna at 0.5 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    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
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

17. 144 MHz single Turnstile Antenna at 0.5λ NEC model.

CM 144 MHz Single Eggbeater Antenna at 0.5 lambda NEC model by Carol F. Milazzo, KP4MD
CM Vertical orientation (using GH command)
CM Frequency = 145.000 MHz
CM 42-side polygon loops
CM Simulated good ground
CM http://www.qsl.net/kp4md/omnihoriz.htm
CE
SY frq=145    'Input frequency MHz
SY d=29.01591    'Input loop diameter inches
SY r=0.5*d    'Calculate loop radius
SY dia=0.5    'Input loop wire dia. inches
SY rad=0.5*dia    'Calculate loop wire radius
SY n=42    'Input n-polygon loop
SY h=40.66136    'Input height inches to 0.5 lambda
GH    1    n    1e-300    1e-300    r    r    r    r    rad    'Form first loop in ground
GM    0    0    90    90-180/n    0    0    0    h    0    'Raise loop center to 0.5 lambda and rotate to orient vertically
GM    1    1    0    0    90    0    0    .25    1    'Rotate loop 90 degrees to form second loop
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    n    0    0    1    0    'Feed point
EX    0    2    n    0    -1    0    0    'Feed point
FR    0    0    0    0    frq    0
EN

18. 144 MHz single Eggbeater Antenna at 0.5λ NEC model.

RESULTS

  1. All antennas had maximum lobe gains between 3.7 and 5.2 dBi of each other at 25º elevation.
  2. The turnstile and Eggbeater Antenna more closely approximated an omnidirectional pattern with 0.6-0.8 dB variation in azimuth radiation while the halo antenna exhibited a 3.2 dB differential in gain between its major and minor axes.
  3. All antenna types showed similar elevation radiation patterns with gains of -1 to -6 dBi toward the zenith.
  4. 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 differences should be considered: 

  1. The minor difference in performance may not warrant incurring the greater construction complexity of the turnstile and eggbeater antenna designs. 
  2. The dimensions of the turnstile and eggbeater antennas need be precise because deviations in the antenna dimensions can significantly skew the radiation patterns.2

Composite of all 144 MHz single Antennas
                      azimuth patterns - horizontal polarization
                      component only.

19. Composite of all 144 MHz single Antennas at 0.5λ azimuth patterns - horizontal polarization component only.

Composite of all 144 MHz single Antennas
                      azimuth patterns - vertical polarization component
                      only.

20. Composite of all 144 MHz single Antennas at 0.5λ azimuth patterns - vertical polarization component only.

REFERENCES

  1. The HO Collinear, A Horizontal Omni, Anderson R, W1HBQ
  2. The Double Turnstile Antenna, Beech J, G8SEQ
  3. Horizontally Polarized Omni-Directional Antennas: Some Compact Choices, Part 1, Cebik, LB, W4RNL
  4. Horizontally Polarized Omni-Directional Antennas: Some Compact Choices, Part 2, Cebik, LB, W4RNL
  5. Experimental Omnidirectional Antennas for 6-Meters, Cebik, LB, W4RNL
  6. 144 MHz Halo Antenna, Milazzo C, KP4MD

APPENDIX: NEC MODEL FILES

  1. 144 MHz single Halo at 0.5λ NEC Model
  2. 144 MHz single Turnstile at 0.5λ NEC Model
  3. 144 MHz single Eggbeater at 0.5λ NEC Model

LINKS

  1. Single Halo, Turnstile and Eggbeater at 0.5λ NEC Models
  2. Single Halo, Turnstile and Eggbeater at 1.0λ NEC Models
  3. Stacked Halo, Turnstile and Eggbeater Antenna NEC Models
  4. Single Turnstile, Triangle and Wheel at 0.5λ NEC Models
  5. Single Turnstile, Triangle and Wheel at 1.0λ NEC Models
  6. Stacked Turnstile, Triangle and Wheel Antenna NEC Models
  7. Omnidirectional Horizontal Antenna Photo Album

Composite of all 144 MHz single Antennas
                      elevation patterns - horizontal polarization
                      component only.

21. Composite of all 144 MHz single Antennas at 0.5λ elevation patterns - horizontal polarization component only.

Composite of all 144 MHz single Antennas
                      elevation patterns - vertical polarization
                      component only.

22. Composite of all 144 MHz single Antennas at 0.5λ elevation patterns - vertical polarization component only.

Summary of Results


Halo
Turnstile
Eggbeater
Cebik Triangle
Cebik Wheel
Single 0.5λ Single 1.0λ
Stacked
Single 0.5λ Single 1.0λ Stacked
Single 0.5λ Single 1.0λ Stacked
Single 0.5λ Single 1.0λ Stacked
Single 0.5λ Single 1.0λ Stacked
Major lobe elevation (degrees)
25
15
15
25
15
15
25
15
15
25
15
15
25
15
15
Major lobe gain (dBi)
2.0-5.2
2.8-6.0
4.8-7.9
2.9-3.7
3.1-4.1
5.8-6.8
3.7-4.3
4.8-5.4
6.3-7.0
4.7-4.9
5.9-6.1
6.8-7.1
4.8-4.9
6.0-6.1
6.9-7.0
Gain at 90º elevation (dBi)
-3.5
-3.5
-40
-1.2
-1.3
-33
-5.4
-5.6
-21
-1000
-1000
-1000
-1000
-1000
-1000
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