Stacked 5-El.-2-m-Yagi, 25 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.

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.

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

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

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

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

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