Details 2-El.-2m 3-El.-2m 4-El.-2m 5-El.-2m 6-El.-2m
7-El.-2m 7-El.-70cm 9-El.-70cm 10-El.-70cm 12-El.-70cm 14-El.-70cm
Stacked 5-El-2m 25-Ohm new 7-El.-2m  25+28-Ohm  new 8-El.-2m  28-Ohm   10-El.-70cm  28-Ohm

Two Versions of stacked 25-Ohm-Yagis (1,80 m and 2,00 m Boom)

 

The picture left shows shows the 4x5-Element-25-Ohm-Yagis with 2-m-boom and a stacking distance of 2,30 m. Two Yagis are connected together with Aircell-5 transformations lines, the two groups are coupled with a power-splitter as described on the "stacking page".

The Yagi-array handles 1 KW HF without any problems and was used for a test in the Alpe-Adria-Contest 2010. The array works excellent with a very good antenna pattern. The measured SWR of the complete group in the common feeding point is <=1,1 beween 144,0 and 144,8 MHz.

At not very good band conditions QSOs from central Germany (450 m ASL) to middle Italy were possible, distance 800- 1000 km.

The Yagis on the picture are built with 8-mm-elements.

The lowest antenna is 6 m above ground, with groundgain you can get 20 dBd gain! The Elevation angle is only 3, the 3-dB-angle vertical is also only 2,8. Plots below!

 

Version 1:

The stacked

 5-Element- 25-Ohm-

2-m-Yagi, Boom 180 cm

Gain of each Yagi is 8,8 dBd, F/B  23 dB

3-dB-angles hor = 49,6, ver = 61,6

Gain of the stacked array 11,5 dBd

3-dB-angles hor = 50,0, ver = 25,4

Stacking distance is 2,20 m

 

With two Yagis of 25-Ohm-impedance an easy stacking is possible. We need two pieces of 5/4-λ-coax-cable with 50 Ω. The 25 Ω at XX are transformed to 100 Ω at XX.

With both cables L1 and L2 parallel we get the 50 Ω for the cable to the TRX. The first 45 cm of the 175,5 cm long pieces are wound to a coax-choke for surpressing common mode currents. The two chokes are in the radiator-box, we do not need coax sockets and connectors.

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The left picture shows the choke,here are 45 cm of the coax wound on a 25-mm-PVC-tube. The right picture shows the 2x50-Ohm resistors (1/2%) parallel. With both chokes and two resistors of 25 Ohm, length of 2x2,04 m Aircell-5 the SWR is 1,0. Between 144,0 and 144,5 MHz the impedance is 50 +/- j 0 Ohm. 

First I started with a length of 213 cm (5/4-lambda * V = 0,82). But this was to long (frequency to deep below 144 MHz). Then I cut the ends in the connection box until the resonance is exactly as you see in the picture of the analyzer. It may be that the individual coax cables differ from the calculated length, therefore a preliminary measurement is very important!

On 143 MHz R= 49 - j 5 Ohm, on 146 MHz R= 51 + j 5 Ohm, the impedance with an analyzer is shown down:

The two connected radiators with 2x 2,04 m Aircell stacked

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Lengths and positions of the elements, radiator always 4mm (exceptional case 6 mm!)

Element

Position

6 mm

4 mm

3,2 mm

2,4 mm

Reflector

0 mm

1032 mm

1034 mm

1037 mm

1040 mm

Radiator

355 mm

993 mm (6 mm)

998 mm

998 mm

998 mm

Director 1

640 mm

950 mm

959 mm

963 mm

968 mm

Director 2

1240 mm

929 mm

939 mm

944 mm

949 mm

Director 3

1780mm

896 mm

907 mm

912 mm

919 mm

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Version 2:

The stacked 5-Element- 25-Ohm-2-m-Yagi, Boom 200 cm

Gain of each Yagi is 9,1 dBd, F/B  27 dB

3-dB-angles hor = 47,2, ver = 56,8

Gain of the stacked array 12,1 dBd

3-dB-angles hor = 47,8, ver = 24,2

Stacking distance is 2,30 m

 

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The construction of DK5EW  and DF8GH 

for the Contest-Station DA0Y in JN48MB

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Lengths and positions of the elements

Element

Position

8 mm 6 mm

4 mm

3,2 mm

2,4 mm

Reflektor

0 mm

1036 mm 1040 mm

1040 mm

1042 mm

1044 mm

Radiator

345 mm

978 mm 982 mm

989 mm

988 mm (4mm)

988 mm (4 mm)

Direktor 1

735 mm

926 mm 934 mm

945 mm

948 mm

953 mm

Direktor 2

1410 mm

922 mm 930 mm

942 mm

944 mm

950 mm

Direktor 3

1970mm

891 mm 898 mm

908 mm

914 mm

920 mm

With the lowest antenna 6 m above ground with medium conductivity and stacking distance of 2,30 m the gain of the array is 20 dBd!

The pattern shows an elevation angle of 3 and a 3-dB-angle of 2,8!