ANOTHER HYBRID ANTENNA FOR 144 MHZ (DUBUS 3/2014)

Slobodan Bukvic, YU7XL

yu7xl@open.telekom.rs

http://www.qslnet.de/member/yu7xl/

Fig. 1: Jozef, YU7AA and his 16 x 8 Ele. Hybrid Antennas

 

In Dubus 1/2011 (1) I described some hybrid antennas. These antennas use a combination of yagi  and quad/oblong elements. Actually, not in the form of well known quagis, instead their reflectors, dipoles and first one or two (or more) directors are yagi elements and all other directors are quad/oblong elements.

As far as I know, no one has tried to present such an antenna type before.

This type of antenna outperforms all existing yagi/quad/oblong antennas and it is worthy of further investigation and construction.

Here I will describe an antenna system consisting of sixteen 8-element hybrid antennas, made of 5 or 6 mm Aluminium rod or tubing.

 

SIXTEEN ANTENNA SYSTEM BY YU7AA

 

In April – May, 2014, my local EME friend  Jozef Fitza, YU7AA, dismantled his 8 x 13 ele antenna system, because he was unsatisfied with its performance in his situation of high city noise, TVI and BCI. He built a new system consisting of sixteen 8-ele hybrids. The system is shown on the pictures 1 and 2.

Jozef is known for his PA and antenna buildings, partly because he spent his life in postal servise as an experienced technician, and partly because he is stubborn enough to complete every-home made job. You know such people: they are usually suspicious to every new idea, so naturally he wanted a classic yagi system. I spent much time persuading him and finally he accepted hybrids, but with one oblong element per antenna only.

The most persuasive thing was the possibility of finally having so-called adaptive polarization, i.e, both horizontal and vertical polarization.

Therefore I made the first 8  ele antenna, and Jozef spent ten days just testing it on EME and tropo. Finding it satisfactory, he immidiatelly started building other antennas, frames, cables…In less than one month, the system was up! You can imagine the work involved, 240 elements had to be cut and put on the booms with plastic holders. Approximately 200 meters of H1000 coaxial cable, plus 10 power dividers, etc, etc…

Now, YU7AA has about half dB less antenna gain than before, but his reception improves significantnly and, finally, he has both H and V polarisations. All antennas (their boomlength is 3.35 metres) are placed in front of the stacking frame and the cables are behind it, so that the supports and cables cannot affect antenna performance. In addition, the antennas are lightweight and there is no need for a counterweight.

 

 

ANTENNA QY20806XL10D3

The construction data data for two similar antennas are given. They are 0.5 meter shorter, so their booms are 2.895 meters long. Three last directors are made as quads and that is the reason why performance is the same (even a bit beter) than the ones used by YU7AA.

If vertical elements are omitted, the antenna can be used just for horizontal polarization, without changing its characteristics.

The antenna layout is shown in fig. 3.

Fig. 3: Layout for 8 Ele. Hybrid Yagis QY20806XL10D3 and QY20805XL10D3

 

As you can see, the driven elements are in the form of a LFA. This reduces possible problem with mutual interaction between horizontal and vertical elements, which occur if folded dipoles had been used. The sketch of the driven loop element is shown in fig. 4.

 

 

Fig. 4 – LFA radiator, dimensions are the same for both, the 5 and 6 mm version.

 

Both linear polarisations are achieved just by adding a set of vertical yagi elements. The vertical elements are placed 20 mm behind the corresponding horizontal elements. Then a small correction is made on the vertical elements to get the same impedance – 200 Ohms.

Important note: All elements are mounted 10 mm over the boom, using suitable plastic holders. Horizontal and vertical elements must cross the same centreline! In practice you should consider the impact of the boom. The impedance remains unchanged, but the rear side of the antenna patterns is altered slightly, which will make antenna temperature a bit higher (about 2 – 3 K).

The tables 1 shows the dimensions:

 

 

Horizontal antenna parts

Vertical antenna parts

 

Ref

DE1

DE2

D1

D2

D3

DQ1

DQ2

DQ3

Ref

DE1

DE2

D1

D2

D3

Position

0

215

345

436

697

1089

1621

2283

2895

0

215

345

436

690

1089

Length

1018

1022

850

940

936

916

527

515

500

1018

1022

850

938

936

916

All vertical parts should be positioned 20 mm behind the corresponding horizontal elements.

After that, director D2 should be moved towards the reflector by 7 mm.

Length of vertical director D1 should be shorter for 2 mm.

All dimensions in mm.

Table 1 – Dimensions for 6 mm version QY20806XL10D3

 

Diagrams for the horizontal part of the antenna QY20806XL10D3:

Fig. 5 a, b, c, d: QY20806XL10D3 Az and El plots, wide and narrow SWR plots (horizontal)

 

Vertical part of the antenna:

 

Fig. 6 a, b, c, d: QY20806XL10D3 Az and El plots, wide and narrow SWR plots (vertical)

 

G

(dBi)

F/B

(dB)

F/Sh

(dBi)

F/Sv (dBi)

Hor

(◦)

Ver

(◦)

Temp

(K)

G/T

(dB)

Tlos

(K)

Bandwidth

for SWR 1.5 (MHz)

Horizontal

12.80

21.68

20.83

17.72

43.2

48.2

256.9

-11.30

3.7

140.000 - 146.300

Vertical

12.82

21.35

17.50

20.67

48.2

43.2

250.4

-11.16

3.7

140.200 – 146.400

Table 3 – Performance data for 6 mm version QY20806XL10D3

Comparison:
This is a modified copy of the VE7BQH Table with antennas of similar boomlength. My antenna is inserted in a proper place in the table, so its characteristics can be compared against other antennas.

TYPE OF

ANTENNA

SINGLE ANTENA

FOUR ANTENNAS IN H-STACK

Boomlength

GAIN

(dBd)

Z

(ohms)

VSWR

Bandwidth

E

(m)

H

(m)

Ga

(dBd)

Tlos

(K)

Ta

(K)

G/T

(dB)

mm

(λ)

QY20806XL10D3/Hor.

2895

1.39

10.65

199.1

1.10:1

3.17

2.38

16.53

3.7

239.5

-5.11

QY20806XL10D3/Vert.

2915

1.40

10.67

200.1

1.10:1

3.06

2.42

16.52

3.7

232.9

-5.00

G0KSC 7LFA

 

1.39

10.62

48.0

1.19:1

2.84

2.49

16.53

1.8

248.9

-5.28

DG7YBN 7

 

1.44

10.59

47.2

1.70:1

2.88

2.47

16.55

4.5

242.7

-5.15

Vine 7 FD

 

1.45

10.56

47.9

1.14:1

2.83

2.46

16.47

8.2

238.6

-5.16

G4CQM 7

 

1.50

10.76

50.7

2.31:1

2.89

2.53

16.69

7.9

239.9

-4.96

CT1FFU 7

 

1.54

10.82

28.0

1.02:1

2.87

2.50

16.70

2.8

237.7

-4.96

DK7ZB 7

 

1.57

11.11

28.4

1.64:1

3.16

2.84

17.13

5.8

272.6

-5.07

IK0BZY 6

 

1.63

11.11

19.5

2.27:1

3.10

2.77

17.04

4.8

266.5

-5.07

Z(ohms) - measured at 144.100 MHz

Bandwidth – VSWR measured at 145.000 MHz

Table 4: Comparison of the QY20806XL10D3 in the VE7BQH G/T table

 

ANTENNA QY20805XL10D3

 

            The layout of this antenna is the same as shown in Fig. 3, and the radiator is the same as shown in fig. 4, even the same material is used – 6 mm diameter Al tubing. All the quad elements are also of 6 mm diameter Al tubing, just the yagi elements are 5 mm diameter Al rods. Everything else is the same as the previous antenna.

Dimensiones are given Table 5:

 

Table 2 – Dimensions for 5 mm version QY20805XL9D3

 

Horizontal antenna parts

Vertical antenna parts

 

Ref

DE1

DE2

D1

D2

D3

DQ1

DQ2

DQ3

Ref

DE1

DE2

D1

D2

D3

Position

0

215

345

436

700

1091

1621

2278

2895

0

215

345

436

693

1091

Length

1020

1022

850

941

935

917

525

512

500

1018

1022

850

940

935

917

All vertical parts should be positioned 20 mm behind the corresponding horizontal elements.

After that, director D2 should be moved closer to reflector by 7 mm.

Length of vertical director D1 should be shorter by 1 mm.

Table 5: Dimensions for the 5 mm version QY 20805XL10D3

 

Horizontal part of the antenna:

Fig. 7 a, b, c, d: QY20805XL10D3 Az and El plots, wide and narrow SWR plots

Vertical part of the antenna:

Fig. 8 a, b, c, d:: QY20805XL10D3 Az and El plots, wide and narrow SWR plots

 

 

 

G

(dBi)

F/B

(dB)

F/Sh

(dBi)

F/Sv (dBi)

Hor

(◦)

Ver

(◦)

Temp

(K)

G/T

(dB)

Tlos

(K)

Bandwidth

for SWR 1.5 (MHz)

Horizontal

12.77

21.00

21.63

17.15

43.6

48.6

258.1

-11.35

3.7

140.000 - 146.700

Vertical

12.79

20.96

16.84

21.55

48.6

43.4

249.7

-11.19

3.7

140.100 – 146.700

Table 6: Performance data for 5 mm version QY20805XL10D3

Comparisons:

This is a modified copy of the VE7BQH Table with antennas of similar boom length. The antenna is inserted in its proper place in the table, so its characteristics can be compared against other antennas.

TYPE OF

ANTENNA

SINGLE ANTENA

FOUR ANTENNAS IN H-STACK

Boomlength

GAIN

(dBd)

Z

(ohms)

VSWR

Bandwidth

E

(m)

H

(m)

Ga

(dBd)

Tlos

(K)

Ta

(K)

G/T

(dB)

mm

(λ)

QY20805XL9D3/Hor

2895

1.39

10.62

198.4

1.07:1

3.32

2.35

16.50

3.7

239.2

-5.14

QY20805XL9D3/Vert.

2915

1.40

10.64

198.1

1.06:1

3.06

2.42

16.52

3.7

232.9

-5.00

G0KSC 7LFA

 

1.39

10.62

48.0

1.19:1

2.84

2.49

16.53

1.8

248.9

-5.28

DG7YBN 7

 

1.44

10.59

47.2

1.70:1

2.88

2.47

16.55

4.5

242.7

-5.15

Vine 7 FD

 

1.45

10.56

47.9

1.14:1

2.83

2.46

16.47

8.2

238.6

-5.16

G4CQM 7

 

1.50

10.76

50.7

2.31:1

2.89

2.53

16.69

7.9

239.9

-4.96

CT1FFU 7

 

1.54

10.82

28.0

1.02:1

2.87

2.50

16.70

2.8

237.7

-4.96

DK7ZB 7

 

1.57

11.11

28.4

1.64:1

3.16

2.84

17.13

5.8

272.6

-5.07

IK0BZY 6

 

1.63

11.11

19.5

2.27:1

3.10

2.77

17.04

4.8

266.5

-5.07

Z(ohms) - measured on 144.100 MHz

Bandwidth – VSWR measured on 145.000 MHz

Table 7: Comparison of the QY20805XL10D3 in the VE7BQH G/T table

 

16 ANTENNA SYSTEM:

 

I suggest stacking distances  of 2.6 metres between antennas in both horizontal and vertical planes. If so, you can expect the following performance (this is calculated for the 5 mm  antenna version, but valid for 6 mm version, too):

 

G

(dBi)

F/B

(dB)

F/Sh

(dBi)

F/Sv (dBi)

Hor

(◦)

Ver

(◦)

Temp

(K)

G/T

(dB)

Tlos

(K)

Bandwidth

for SWR 1.5 (MHz)

Horizontal

24.65

21.90

13.34

9.6

13.06

9.8

232.8

+0.98

3.7

140.000 - 146.300

Vertical

24.66

21.58

13.05

13.34

9.8

9.6

225.8

+1.12

3.7

140.200 – 146.400

Table 8: Performance data of the 16 x QY20805XL10D3 stack

 

HORIZONTAL PATTERNS

Fig 9a and 9b: Diagrams of the horizontal part of the 16 x QY20805XL10D3 stack

 

VERTICAL PATTERNS

Fig 10a and 10b: Diagrams of the vertical part of the 16 x QY20805XL10D3 stack

 

 

 

Conclusion:

This is an easy and lightweight compact antenna system for EME and tropo DX on 144 MHz. Though 5 power dividers are necessary, and phasing harness is rather complex,  it should be easier for building than, for example, a corresponding 4-antenna system which includes 5 to 6 WL antennas at least. Also, in my experience, such an antenna system is more stable and balanced in windy condition.

 

Boban, YU7XL

http://www.qslnet.de/member/yu7xl/

yu7xl@open.telekom.rs

 

Reference

(1) Slobodan Bukvic, YU7XI, Hybrid LFA Yagi Oblong Antennas, DUBUS 1/2011, pp.16

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