Systematic Investigation of a large fixed 145 MHz Yagi Group
The following investigations have been performed to lay the base for a larger group of yagis for the 145 MHz band to be used for contest operation at mount Schneeberg, JO50WB. It has been inspired by the antenna group used by the DR9A contest group at their portable contest QTH. Mount Schneeberg is the highest peak of the Fichtelgebirge located in the northern part of Bavaria close to the Czech border. It is very demanding with respect to weather condition and high-frequency environment. Antennas will have to be setup in spring and removed in autumn since they won’t survive the winter storms.
Acknowledgements
I would like to thank the following persons for their extensive and unconditional support:
- Martin, DK7ZB: for developing the single antennas and adapting them to our needs
- Henning, DF9IC: for sharing its enormous technical expertise with an advanced beginner
In addition there has been support by solving smaller problems with the simulation environment or understanding the results obtained by
- Peter, DL2NBU
- Sigi, DL8NAS
- Hubert, DK3RU
Introduction
The Goal
Antenna group to be used during contest operation with the following characteristics:
- omni-directional radiation pattern
- reasonable gain
- to be mounted on a portable surplus mast (lowered to ground during non-contest periods)
Technical Solution
- several individual groups of four 5 or 6-element antennas vertically stacked
- individual groups distributed horizontally
- mast side mounting of the individual antennas
Simulation Environment
All simulations have been performed with the following simulation environment:
- HP Workstation W3520 @2.67GHz
- 16GB RAM
- Windows 7
- 4Nec2 Version 5.9.3
- maximum number of ‘EX cards’ increased to 36
- maximum number of ‘LD cards’ increased to more than 192
Single Yagi Survey
Antennas under Survey
Antennas with a maximum of about 2.5 m overall boom length and reasonable gain to horizontal beam width value have been considered for the project. Thus, the following 5- and 6-element DK7ZB antennas have been investigated:
Description | Ref | DE | Dir #1 | Dir #2 | Dir #3 | Dir #4 | |
---|---|---|---|---|---|---|---|
5-el 28Ohm OWM Yagi | Position [mm] | 0 | 315 | 545 | 1025 | 1480 | -- |
Length [mm] | 1024 | 983 | 939 | 927 | 896 | -- | |
6-el 28Ohm OWM Yagi | Position [mm] | 0 | 275 | 420 | 840 | 1495 | 2065 |
Length [mm] | 1020 | 1000 | 959 | 917 | 911 | 871 | |
5-el 28Ohm Yagi | Position [mm] | 0 | 350 | 710 | 1295 | 1780 | -- |
Length [mm] | 1022 | 962 | 919 | 914 | 885 | -- | |
6-el 28Ohm Yagi | Position [mm] | 0 | 390 | 640 | 1150 | 1785 | 2380 |
Length [mm] | 1017 | 971 | 935 | 907 | 905 | 876 |
The geometrical data of all antennas has been taken from the web page of DK7ZB (https://dk7zb.darc.de/) or obtained by private communication.
Results
DK7ZB 5-Element Antenna (l = 1.78 m)
4NEC2 Input: | Geometry File | |
Frequency: | 144.3 MHz | |
Impedance: | (27.7 - j 0.6) Ω | |
Gain: | 11.1 dBi | |
F/B: | 20 db | |
Radiation Pattern: | horizontal: Invalid shortcode 3dB-Angle: 48° | vertical: Invalid shortcode 3dB-Angle: 60° |
DK7ZB 5-Element OWM Antenna (l = 1.48 m)
4NEC2 Input: | Geometry File | |
Frequency: | 144.3 MHz | |
Impedance: | (27.3 - j 1.0) Ω | |
Gain: | 10.5 dBi | |
F/B: | 30 db | |
Radiation Pattern: | horizontal: Invalid shortcode 3dB-Angle: 50° | vertical: Invalid shortcode 3dB-Angle: 64° |
DK7ZB 6-Element Antenna (l = 2.40 m)
4NEC2 Input: | Geometry File | |
Frequency: | 145.0 MHz | |
Impedance: | (32.5 + j 0.7) Ω | |
Gain: | 12.1 dBi | |
F/B: | 23 db | |
Radiation Pattern: | horizontal: Invalid shortcode 3dB-Angle: 44° | vertical: Invalid shortcode 3dB-Angle: 52° |
DK7ZB 6-Element OWM Antenna (l = 2.07 m)
4NEC2 Input: | Geometry File | |
Frequency: | 144.3 MHz | |
Impedance: | (27.8 + j 0.7) Ω | |
Gain: | 11.5 dBi | |
F/B: | 38 db | |
Radiation Pattern: | horizontal: Invalid shortcode 3dB-Angle: 48° | vertical: Invalid shortcode 3dB-Angle: 58° |
Note: This antenna has been advertised as a 28Ω-Yagi. However simulations show a radiation resistance of about 33 Ω in resonance. However, this won’t be further investigated since this antenna won’t be of interest in this project. See further down for details.
Discussion
The slightly higher gain of the standard yagis results in a radiation pattern with increased side lobes and larger mechanical dimensions. So, it seems that the OWM-yagis will be more promising with respect to the goal of the project.
The 6-element standard yagi will be excluded completely from further investigations since the mechanical length of almost 2.5 m poses a great challenge in pre-mast mounting.
Vertical Stacking
The mechanical length of the antennas of interest are all about in the range of about an wave length. Thus, the standard DL6WU formula would fail for the determination of an optimal vertical stacking distance. So, simulations have been carried to characterize the resulting antenna stacks as function of the stacking distance.
DK7ZB 5-Element Antenna (l = 1.78 m)
4NEC2 Input: | Geometry File | |
Frequency: | 144.3 MHz | |
Stacking Distance | Horizontal Pattern | Vertical Pattern |
h = 1.80 m Impedance: (25.2+ j 3.7) Ω Gain: 15.8 dBi F/B: 16 dB | Invalid shortcode 3dB-Angle: 46° | Invalid shortcode 3dB-Angle: 14° |
h = 1.90 m Impedance: (28.7 + j 3.3) Ω Gain: 16.3 dBi F/B: 28 dB | Invalid shortcode 3dB-Angle: 48° | Invalid shortcode 3dB-Angle: 14° |
h = 2.00 m Impedance: (30.1 + j 1.4) Ω Gain: 16.7 dBi F/B: 27 dB | Invalid shortcode 3dB-Angle: 50° | Invalid shortcode 3dB-Angle: 14° |
h = 2.10 m Impedance: (30.1 + j 0.2) Ω Gain: 17.0 dBi F/B: 24 dB | Invalid shortcode 3dB-Angle: 50° | Invalid shortcode 3dB-Angle: 12° |
h = 2.20 m Impedance: (29.9 - j 0.7) Ω Gain: 17.2 dBi F/B: 22 dB | Invalid shortcode 3dB-Angle: 50° | Invalid shortcode 3dB-Angle: 12° |
h = 2.30 m Impedance: (29.5 - j 1.4) Ω Gain: 17.3 dBi F/B: 21 dB | Invalid shortcode 3dB-Angle: 50° | Invalid shortcode 3dB-Angle: 12° |
h = 2.40 m Impedance: (29.0 - j 1.9) Ω Gain: 17.3 dBi F/B: 20 dB | Invalid shortcode 3dB-Angle: 50° | Invalid shortcode 3dB-Angle: 12° |
DK7ZB 5-Element OWM Antenna (l = 1.48 m)
4NEC2 Input: | Geometry File | |
Frequency: | 144.3 MHz | |
Stacking Distance | Horizontal Pattern | Vertical Pattern |
h = 1.80 m Impedance: (25.8 + j 0.37) Ω Gain: 15.9 dBi F/B: 15 dB | Invalid shortcode 3dB-Angle: 50° | Invalid shortcode 3dB-Angle: 15° |
h = 1.90 m Impedance: (28.2 - j 0.25) Ω Gain: 16.2 dBi F/B: 17 dB | Invalid shortcode 3dB-Angle: 52° | Invalid shortcode 3dB-Angle: 14° |
h = 2.00 m Impedance: (28.1 - j 0.8) Ω Gain: 16.5 dBi F/B: 18 dB | Invalid shortcode 3dB-Angle: 52° | Invalid shortcode 3dB-Angle: 14° |
h = 2.10 m Impedance: (27.9 - j 1.0) Ω Gain: 16.6 dBi F/B: 19 dB | Invalid shortcode 3dB-Angle: 52° | Invalid shortcode 3dB-Angle: 12° |
h = 2.20 m Impedance: (27.8 - j 1.0) Ω Gain: 16.7 dBi F/B: 20 dB | Invalid shortcode 3dB-Angle: 52° | Invalid shortcode 3dB-Angle: 12° |
h = 2.30 m Impedance: (27.9 - j 1.1) Ω Gain: 16.7 dBi F/B: 20 dB | Invalid shortcode 3dB-Angle: 52° | Invalid shortcode 3dB-Angle: 12° |
DK7ZB 6-Element OWM Antenna (l = 2.07 m)
4NEC2 Input: | Geometry File | |
Frequency: | 144.3 MHz | |
Stacking Distance | Horizontal Pattern | Vertical Pattern |
h = 1.80 m Impedance: (27.5 - j 3.8) Ω Gain: 16.5 dBi F/B: 22 dB | Invalid shortcode 3dB-Angle: 46° | Invalid shortcode 3dB-Angle: 14° |
h = 1.90 m Impedance: (25.7 - j 1.7) Ω Gain: 16.8 dBi F/B: 28 dB | Invalid shortcode 3dB-Angle: 46° | Invalid shortcode 3dB-Angle: 14° |
h = 2.00 m Impedance: (25.9 - j 0.2) Ω Gain: 17.1 dBi F/B: 33 dB | Invalid shortcode 3dB-Angle: 46° | Invalid shortcode 3dB-Angle: 14° |
h = 2.10 m Impedance: (26.3 + j 0.6) Ω Gain: 17.3 dBi F/B: 34 dB | Invalid shortcode 3dB-Angle: 48° | Invalid shortcode 3dB-Angle: 12° |
h = 2.20 m Impedance: (26.7 + j 1.0) Ω Gain: 17.5 dBi F/B: 33 dB | Invalid shortcode 3dB-Angle: 48° | Invalid shortcode 3dB-Angle: 12° |
h = 2.30 m Impedance: (27.1 + j 1.3) Ω Gain: 17.6 dBi F/B: 33 dB | Invalid shortcode 3dB-Angle: 48° | Invalid shortcode 3dB-Angle: 12° |
h = 2.40 m Impedance: (27.6 + j 1.3) Ω Gain: 17.7 dBi F/B: 33 dB | Invalid shortcode 3dB-Angle: 48° | Invalid shortcode 3dB-Angle: 12° |
Discussion
Horizontal Distribution
Full Group Survey
Conclusion
Antenna used has been developed by Martin, DK7ZB. Construction data received by private communication.
Description
- 28-Ohm-OWM-Yagi
- 6 elements
- 10 mm element diameter
- Geometry File used: DK7ZB-6el-OWM_single_elements_10mm.nec
Results
- clean horizontal radiation pattern, good side lobe suppression
- excellent F/B value
Total Gain | Horizontal | Vertical |
---|---|---|
Invalid shortcode | Invalid shortcode | |
Gain [dBi] | 11.5 | |
F/B [dB] | 37.7 | |
3dB Angle [°] | 48 | 38 |
2x Vertically Stacked
Description
- 2 antennas vertically stacked w/ variable stacking distance
- Geometry File used: DK7ZB-6el-OWM_ele10mm_4-fold-vertical.nec
Results
- horizontal radiation pattern un-affected
- gain increases by about 3 dB as theoretically predicted
- F/B value decreases slightly
- proposed stacking distance: 2.20 … 2.30 m
Horizontal | Vertical | |
---|---|---|
h = 1.9 m | Invalid shortcode | Invalid shortcode |
Gain: 14.1 dBi | F/B: 46 dB | |
h = 2.0 m | Invalid shortcode | Invalid shortcode |
Gain: 14.3 dBi | F/B: 40 dB | |
h = 2.1 m | Invalid shortcode | Invalid shortcode |
Gain: 14.4 dBi | F/B: 38 dB | |
h = 2.2 m | Invalid shortcode | Invalid shortcode |
Gain: 14.5 dBi | F/B: 36 dB | |
h = 2.3 m | Invalid shortcode | Invalid shortcode |
Gain: 14.5 dBi | F/B: 35 dB |
4x Vertically Stacked
Description
- 4 antennas vertically stacked w/ variable stacking distance
- Geometry File used: DK7ZB-6el-OWM_ele10mm_4-fold-vertical.nec
Results
- horizontal radiation pattern un-affected
- gain increases by about 6 dB as theoretically predicted
- F/B value decreases slightly
- proposed stacking distance: 2.10 … 2.20 m
Horizontal | Vertical | |
---|---|---|
h = 1.9 m | Invalid shortcode | Invalid shortcode |
Gain: 16.8 dBi | F/B: 28 dB | |
h = 2.0 m | Invalid shortcode | Invalid shortcode |
Gain: 17.1 dBi | F/B: 3 dB | |
h = 2.1 m | Invalid shortcode | Invalid shortcode |
Gain: 17.3 dBi | F/B: 34 dB | |
h = 2.2 m | Invalid shortcode | Invalid shortcode |
Gain: 17.5 dBi | F/B: 33 dB | |
h = 2.3 m | Invalid shortcode | Invalid shortcode |
Gain: 17.6 dBi | F/B: 33 dB |
6x Vertically Stacked
Description
- 6 antennas vertically stacked w/ variable stacking distance
- Geometry File used: DK7ZB-6el-OWM_ele10mm_6-fold-vertical.nec
Results
- horizontal radiation pattern un-affected
- gain increases by about 8 dB as theoretically predicted
- F/B value decreases slightly
- proposed stacking distance: 2.20 … 2.30 m
Horizontal | Vertical | |
---|---|---|
h = 1.9 m | Invalid shortcode | Invalid shortcode |
Gain: 18.3 dBi | F/B: 20 dB | |
h = 2.0 m | Invalid shortcode | Invalid shortcode |
Gain: 18.8 dBi | F/B: 26 dB | |
h = 2.1 m | Invalid shortcode | Invalid shortcode |
Gain: 19.1 dBi | F/B: 30 dB | |
h = 2.2 m | Invalid shortcode | Invalid shortcode |
Gain: 19.3 dBi | F/B: 32 dB | |
h = 2.3 m | Invalid shortcode | Invalid shortcode |
Gain: 19.4 dBi | F/B: 32 dB | |
h = 2.4 m | Invalid shortcode | Invalid shortcode |
Gain: 19.4 dBi | F/B: 32 dB |
2x Horizontally Distributed
Description
- 2 antennas horizontally distributed w/ variable angle on a circle with radius r
- Geometry File used: DK7ZB-6el-OWM_ele10mm_2-fold-horizontal.nec
Results
- antennas act – almost – independently, checked also by several radii
- gain drops by roughly 3 dB for 2 antennas as theoretically predicted
Horizontal | Vertical | |
---|---|---|
r = 1.0 m, φ = 90° | Invalid shortcode | Invalid shortcode |
Gain: 8.5 dBi | ||
r = 1.0 m, φ = 180° | Invalid shortcode | Invalid shortcode |
Gain: 8.6 dBi |
4x Horizontally Distributed
Description
- 4 antennas horizontally equally distributed
- Geometry File used: DK7ZB-6el-OWM_ele10mm_4-fold-horizontal.nec
Results
- antennas act – almost – independently, checked also by several radii
- gain drops by roughly 6 dB for 4 antennas as theoretically predicted
Horizontal | Vertical | |
---|---|---|
r = 1.0 m, φ = 90° | Invalid shortcode | Invalid shortcode |
Gain: 5.5 dBi |