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 new 10-El.-70cm  28-Ohm new

Version 1: The 7-Element-28Ohm-Leightweight-Yagi for 2m

Gain 11,0 dBd, F/B 25 dBd

Boom 3,30 m

Stacking distance 2,80 m

3dB-angles: 39,4 hor, 44,4 ver

It is possible to build the well known 7-El.-28-Ohm-Yagi with an aluminium-boom 20x1,5mm. The coax socket ist grounded to the boom with a screw and an aluminium angle.

Elements

Ref

Rad (8mm)

Dir 1

Dir 2

Dir 3

Dir 4

Dir 5

Position

0mm

320mm

595mm

1145mm

1825mm

2615mm

3260mm

L (3,2mm)

1016mm

976mm

964mm

943mm

925mm

928mm

913mm

L (4mm)

1014mm

976mm

961mm

938mm

920mm

923mm

908mm

Version 2: The 7-Element-25-Ohm-Leightweight-Yagi for stacking

Boom 3,40 m   Broadband

Gain 11,05 dBd, F/B 26 dB

3-dB-Angles:  hor 39,6   ver 44,6

Stacking distance 2,80 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. I use Aircell-5 with 2x2,04 m.

With both cables L1 and L2 parallel we get the 50 Ω for the cable to the TRX. The first 45 cm of the 204 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 picture on the right side down shows the measuring of the stacking cable with 2x 50-Ω- resistors (0,5%) parallel for 25 Ω impedance.

 

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:

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

Lengths and positions of the elements, radiator always 4mm

Element

Position

8 mm

6 mm

4 mm

3,2 mm

Reflector

0 mm

1020 mm

1022 mm

1024 mm

1027 mm

Radiator

300 mm

974 mm (8 mm)

982 mm (6 mm)

984 mm

986 mm (4 mm)

Director 1

645 mm

937 mm

946 mm

953 mm

954 mm

Director 2

1245 mm

914 mm

924 mm

930 mm

937 mm

Director 3

1945 mm

896 mm

908 mm

918 mm

922 mm

Director 4

2750 mm

894 mm

904 mm

916 mm

920 mm

Director 5

3380 mm

892 mm

903 mm

913 mm

917 mm