MY TWEEN BOOM YAGI ANTENNAS FOR 144 MHZ

         

         

You have a small house yard and there is no room for a bigger antenna? Probably, the tween boom antenna is the answer. The characteristics of a 10 metres long yagi antenna can be achieved with a 6.5 to 7 metres long tween boom antenna   .

This is a little bit unusual approach to making high gain antennas. The point is to build two vertically stacked yagi antennas, which stacking distance is small.. The reflector, the radiator (and sometimes the first director) are common for both yagis.

The small distance stacking gives not so great gain increase. It is usually around 1 dB over a single yagi (maximum 1.5 dB), but there are other benefits of such configuration.

As seen, the booms should be slightly bent toward each other for best performance. The vertical distance after bending is not critical, so a little error in bending is negligible. However, the horizontal distance between elements should be kept very precise, as given in the tables for every particular antenna. This means, the element distance/position is given on the centerline between the booms and should be converted onto vertical projections on both booms precisely.

Every antenna model has double quad radiator. I have designed many tweenboom antennas with open, folded or LFA radiator, but found the double quad the best shape of radiator. The antenna with such a radiator gives up to 0.5 dB additional gain in comparison to other radiator forms.

One can say this configuration is hard for building. No, it is not! Both booms strengthen each other, and both booms are additionally reinforced by mounting on a vertical frame holder. At the ends, both booms are finally squeezed to maintain the necessary boom bending, which gives some more strength. You can, even, use a very small diameter boom.

I built a 8 meter long double boom yagi for 50 MHz using 25 mm Aluminum tubes, 1 mm thick. This antenna was standing on the tower for three years with no problems with strongest winds at all. Note, the 25 mm tube, 1 mm thick, 6 meter long, is just 1 kilo of Aluminum. This antenna gain was nearly 14 dBi. For such gain level, a classic style yagi should be 11 to 12 meters long - which means much thicker boom tube, plus boom reinforcements.

Here you can see the photos which speaks more than words. I built them with LFA radiators. Later on I got awared that double quad performs better. so now I am preparing to replace LFA radiators with double quad ones. This antenna is for 144 MHz, 5.625 meters long. Booms are 25/1 mm diameter, soft Aluminum!

If you want the same performance with classic style yagis, you have to choose a yagi 8 to 9 meters long. Imagine how strong its boom should be.

Further bellow you can see my EME system consisted of four such antennas. I started working with them in October 2016 and it is too early to speak about experiences in mechanical behaviour. Although, I can compare them to my previous antennas 16 x 9 ele hybrids, which were blown in June 2016 by a tornado (who sais there have never been tornados in my area???).

For me they are performing very satisfying. The only lack is XPOL is not possible with this antenna type.

Down in the Table you can find the list of my best tweenboom antennas. You can compare them to YU7EF antennas and see all benefits they offer. For example, 6 elements YU7EF yagi gives the G/T worse for 2.4 dB! than X21205XL4QQ. With longer booms, the difference becomes lower. In my opinion, tweenboom antennas extremely pay off within 3 WL of boom length, though one can estimate reasonable to build even longer tweens. Look at the Table and think.

Have a nice time building and DXing.

 

Note: KF2YN correction is applied on all models. The formula should be applied because the antenna modelling software (NEC/EZNEC) does not contain the KF2YN formula and cannot fight off the convergence error caused by tappered or sharply bent elements. After applying, antenna data are standardized and can be put into VE7BQH table alongside with other competing antennas. Therefore, do not be confused with different results of gain in tables and in diagrams! This correction gives the real gain for ALUMINUM. Except for gain, the differences in other parameters (F/B, F/S etc) are minor and can be neglected.

 

 

Antenna X21705XL1 under the test

 

 

The same antennas stacked vertically at 5.00 meters and horizontally at 4.40 meters

 

 

 

DOUBLE BOOM ANTENNAS FOR 144 MHz YU7XL

(INSERTED DATA FOR YU7EF ANTENNAS FOR COMPARISON)

 

ANTENNA

TYPE

No of ele

Ǿ

(mm)

Length

(mm)

Type

Gain

(dB)

F/B

(dB)

F/Sh

(dB)

F/Sv

(dB)

H lobe

(◦)

V lobe

(◦)

TA

(◦K)*

G/T

(dB)*

Tloss

(dB)

Δf (SWR=1.5)

Lower

Upper

X21005XL8Q 10 5 1645 Q 12.37 26.84 - 17.33 48.8 44.6 254.0 -11.68 4.2 140.700 146.400
X21006XL3Q 10 6 1645 Q 12.42 24.80 - 17.38 48.6 44.6 252.8 -11.60 3.6 141.400 146.700
X21008XL3Q 10 8 1645 Q 12.57 23.17 - 15.82 48.2 42.5 250.6 -11.42 3.0 141.300 146.300
X21010XL6Q 10 10 1645 Q 12.66 23.18 - 15.51 48.2 41.4 249.8 -11.32 2.7 141.600 146.500

X21205XL4Q

12

5

2305

Q

13.44

34.34

-

16.14

44.5

38.1

235.8

-10.29

4.5

141.800

146.800

X21206XL2Q

12

6

2305

Q

13.46

32.68

-

16.82

44.5

37.9

233.8

-10.22

3.9

142.200

146.400

X21208XL5Q

12

8

2305

Q

13.50

40.36

-

16.96

44.5

37.7

233.1

-10.18

3.3

141.200

146.400

X21210XL4Q

12

10

2305

Q

13.54

26.94

-

17.33

44.6

37.0

230.8

-10.09

2.7

141.400

146.600

EF0206-5

6

5

2377

Classic

50Ώ

11,82

26.99

25.06

14,50

46,2

55,4

282.6

-12,69

5.2

140,200

145,300

X21405XL5Q 14 5 2945 Q 14.16 34.87 - 16.16 41.8 34.4 225.8 9.38 5.1 140.000 146.700
X21406XL4Q 14 6 2945 Q 14.16 38.35 - 16.30 41.8 34.4 225.1 9.36 4.8 140.000 146.600
X21408XL4Q 14 8 2945 Q 14.20 34.09 - 16.59 41.8 34.2 224.5 9.32 3.6 139.400 147.100
X21410XL9Q 14 10 2945 Q 14.23 32.27 - 16.87 41.8 33.8 224.4 9.28 3.0 139.200 147.300

X21605XL2Q

16

5

3605

Q

14.88

26.76

-

16.86

38.2

30.8

228.9

-8.71

6.0

141.600

147.200

X21606XL2Q

16

6

3605

Q

14.90

26.96

-

17.20

38.4

30.3

227.5

-8.67

5.4

141.200

146.800

X21608XL2Q

16

8

3605

Q

14.94

28.67

25.37

16.48

38.7

29.8

225.6

-8.60

4.5

141.000

146.600

X21610XL2Q

16

10

3605

Q

14.96

26.85

26.45

15.95

38.6

30.6

225.3

-8.57

3.3

141.000

146.700

EF0207-5

7

5

3274

Classic

50Ώ

12,83

26.54

25.33

17,35

42,6

49.0

255,6

-11,25

6.1

140,400

145,100

EF0208-5

8

5

3900

Classic

50Ώ

13,42

22,43

22,12

15,37

40,2

45,2

248,9

-10,54

5.2

141,220

145,490

X21805XL2Q

18

5

4365

Q

15.48

27.69

24.23

16.69

36.2

28.7

224.4

-8.03

6.0

141.800

147.600

X21806XL3Q

18

6

4365

Q

15.44

29.42

25.36

16.37

36.6

29.6

222.6

-8.04

4.5

142.100

148.400

X21808XL3Q

18

8

4365

Q

15.51

29.31

24.60

16.40

36.4

29.2

222.9

-7.97

3.9

141.500

147.700

X21810XL4Q

18

10

4365

Q

15.54

25.94

22.78

17.32

36.2

28.2

223.3

-7.95

3.6

141.000

146.300

EF0209-5

9

5

4490

Classic

50Ώ

13.97

22.69

22,63

16,67

38.0

42,4

240.3

-9.84

4.9

140,100

145,480

X22005XL5Q

20

5

5165

Q

15.85

33.94

23.14

19.14

34.0

28.8

217.7

-7.53

5.4

141.400

146.300

X22006XL3Q

20

6

5165

Q

15.90

27.11

21.83

19.76

33.6

28.0

219.2

-7.51

5.1

142.000

146.200

X22008XL4Q

20

8

5205

Q

15.92

34.43

23.86

18.27

33.8

28.8

218.6

-7.48

3.0

140.600

146.900

X22010XL6Q

20

10

5205

Q

15.97

32.96

22.79

19.06

33.4

28.2

218.4

-7.42

2.7

140.300

146.500

EF0210-5

10

5

5290

Classic

50Ώ

14,64

21.81

21.98

17,33

35.0

38,4

234.4

-9.05

7.0

143.000

144.900

EF0211B-5

11

5

5980

Classic

50Ώ

15,01

29,44

21,13

17,11

33,8

36,8

230.1

-8,61

6.7

140,600

145,210

X22205XL3Q

22

5

5985

Q

16.38

38.61

23.00

18.02

31.8

26.4

219.9

-7.04

6.3

141.800

146.600

X22206XL2Q

22

6

5985

Q

16.39

30.83

20.96

18.80

31.5

26.0

219.6

-7.03

5.7

142.200

146.400

X22208XL3Q

22

8

5985

Q

16.44

31.24

17.25

18.98

31.8

26.6

217.9

-6.94

3.9

141.600

147.600

X22210XL3Q

22

10

5985

Q

16.44

30.36

-

18.89

31.6

26.2

218.1

-6.95

3.3

142.200

146.800

                               

EF0211-5

11

5

6325

Classic

50Ώ

15,12

22.29

22.38

18,30

33,8

36,8

225.5

-8,41

.7.0

142,500

144,750

X22405XL2Q 24 5 6725 Q 16.78 31.70 29.44 18.05 30.6 26.2 219.9 -6.64 6.3 140.400 146.500
X22406XL2Q 24 6 6725 Q 16.80 31.17 27.97 19.02 30.6 24.8 220.1 -6.63 6.0 141.000 146.300

X22408XL1Q

24

8

6725

Q

16.81

31.51

29.44

18.11

30.4

25.6

218.8

-6.59

3.9

140.600

147.700

X22410XL2Q

24

10

6725

Q

16.83

33.09

28.13

18.70

30.2

25.0

219.0

-6.57

3.6

140.200

147.200

EF0212-5

12

5

7260

Classic

50Ώ

15,78

22.38

20,22

16,79

31,4

33,6

224,4

-7.73

6.7

143,300

144,820

X22605XL1Q

26

5

7505

Q

17.10

29.08

15.98

16.59

29.4

25.0

221.1

-6.34

5.1

141.400

148.600

X22606XL1Q

26

6

7505

Q

17.17

27.23

15.08

17.21

29.0

24.4

220.5

-6.26

4.8

141.000

148.000

X22608XL1Q

26

8

7505

Q

17.15

28.26

15.39

18.18

28.8

24.0

218.8

-6.25

4.5

140.600

146.600

X22610XL1Q

26

10

7505

Q

17.20

28.92

14.95

18.00

28.8

24.2

219.1

-6.21

3.3

140.000

146.400

EF0213M-5

13

5

7940

Classic

50Ώ

15.98

26.51

22.08

19.08

30.8

32.8

225.3

-7.55

8.1

140.500

146.000

EF0213-5

13

5

8150

Classic

50Ώ

16,19

23.95

20.22

17.3

30.0

31,8

222.5

-7.28

8.1

143,660

144,620

X22805XL1Q

28

5

8285

Q

17.44

30.58

15.58

16.26

28.0

24.0

221.7

-6.01

5.1

141.600

148.300

X22806XL1Q

28

6

8285

Q

17.50

26.23

14.98

16.57

27.6

23.4

221.2

-5.95

5.1

142.000

147.700

X22808XL1Q

28

8

8285

Q

17.49

27.26

16.82

17.31

28.2

24.0

218.6

-5.91

3.9

142.000

147.000

X22810XL1Q

28

10

8285

Q

17.53

26.62

16.12

18.02

27.8

23.4

218.5

-5.86

3.6

142.000

146.200

X23005XL1Q

30

5

9065

Q

17.73

39.42

16.03

15.58

27.0

23.2

221.7

-5.73

5.1

140.800

148.000

X23006XL1Q

30

6

9065

Q

17.80

32.22

15.39

15.97

26.6

22.6

220.3

-5.62

5.1

141.600

147.400

X23008XL1Q

30

8

9065

Q

17.81

33.94

16.36

17.05

26.8

22.6

217.2

-5.56

4.2

141.800

146.500

X23010XL1Q

30

10

9065

Q

17.82

36.92

16.48

17.58

26.8

22.6

217.3

-5.55

3.6

141.200

146.300

EF0214-5

14

5

9100

Classic

50Ώ

16,64

22,72

20,34

17,69

28,4

30,2

222,7

-6.84

9.3

143,720

144,620

X23205XL1Q

30

5

9845

Q

18.03

42.07

15.56

15.51

26.0

22.2

221.3

-5.42

5.4

141.000

148.100

X23206XL1Q

30

6

9845

Q

18.08

35.81

14.93

15.58

25.6

21.6

219.8

-5.34

5.4

141.000

147.400

X23208XL1Q

30

8

9845

Q

18.09

34.88

15.10

16.12

25.6

21.5

217.9

-5.29

4.8

141.000

146.700

X23210XL1Q

30

10

9845

Q

18.10

41.67

16.39

17.00

25.8

21.7

216.5

-5.25

4.5

140.800

146.500

EF0215-5

15

5

10060

Classic

50Ώ

17,05

24.96

19.42

17.01

26,8

28.2

220.7

-6,39

10.2

143,750

144,460