Construction Details

2-El.-10m-50Ohm

2-El.-12m-12Ohm

2-El-12m-28Ohm

Dualband 12/17m

2-El.-15m-50Ohm

2-El.-17m-28Ohm

2-El.-20m-28Ohm

2-El.-30m-28Ohm

Dualband 10/15m

2-Element parasitic Yagis by DK7ZB for the Shortwave-Bands 10m-30m

Details of a dismantable Yagi built by DL2RMC for portable use see down

Details of a 20m-Yagi by F4EKQ:        http://enduro.civaux.free.fr/antenne.htm

No other antenna has a better relation between gain and expense than the 2-Element-Yagi. One element additional to the dipole will give you 4dB gain. Each further element will give much more mechanical problems and the increase in gain is only 1-2dB for the same bandwidth. What says the ARRL-Antenna-Book about this antenna? "The must bang for the buck". Right!

Because the 10m, 15m and 20m-Bands need a greater bandwidth, the radiation resistance must be higher than for the smaller WARC-Bands. Therefore we take the Yagis with radiator-reflector and 50Ohms for 10m (greatest bandwidth), 28Ohms for 15 and 20m and the Yagis with radiator-director and 28Ohms for the WARC-Bands.

If you have a height above ground of 10m or higher for a 12m-Yagi, you can try a 12,5Ohm-type for that band. The antenna needs a very clear surrounding! With a very short boom and small bandwidth you get very high F/B.

 Gain, F/B, Boomlength and Elements of the 50-Ohm-Yagi with Reflector

Band

Impedance

Gain

F/B

Boom

Radiator

Reflector

10m

50Ohm

4,0dBd

10,5dB

1,76m

4,93m

5,36m

 Gain, F/B, Boomlength and Elements of the 28-Ohm-Yagis with Reflector

Band

Impedance

Gain

F/B

Boom

Radiator

Reflector

15m

28Ohm

4,2dBd

10dB

1,61m

6,87m

7,22m

20m

28Ohm

4,0dBd

10dB

2,30m

10,26m

11,08m

Gain, F/B, Boomlength and Elements of the 28-Ohm-Yagis with Director

Band

Gain

F/B

Boom

Radiator

Director

12m

4,3dBd

14,5dB

1,18m

6,05m

5,60m

17m

4,5dBd

13,5dB

1,70m

8,32m

7,80m

30m

4,4dBd

14dB

3,00m

14,92m

14,04m

  Gain, F/B, Boomlength and Elements of the 12,5-Ohm-Yagi for 12m with Director

Band

Gain

F/B

Boom

Radiator

Director

12m

4,4dBd

>25dB

0,67m

6,09m

5,78m

The antennas are fed with the DK7ZB-match .

 A quarter-wave choke of coax is grounded at the socket.

50Ohm: Single Lambda/4*V-coax 50Ohm

28 Ohm: 2xLambda/4*V-coax 75Ohm parallel

12,5 Ohm: 2xLambda/4*V-coax 50Ohm parallel

 

Length of the cables see table below

Lengths of the Lambda/4-coax for the choke:

Band Lambda Full-PE  V=0,667 Foam-PE  V=0,82 (CATV)
10 m 10,60 m 1,77 m 2,17 m
12 m 12,03 m 2,00 m 2,47 m
15 m 14,18 m 2,36 m 2,90 m
17 m 17,53 m 2,76 m 3,60 m
20 m 21,18 m 3,53 m 4,34 m
30 m 29,62 m 4,94 m 6,07 m

The dismantable Yagi by DL2RMC for portable use 

The Yagi of Tom, DL2RMC during his expedition to Corsica island (TK/DL2RMC)

He has a cheap and simple construction similiar to my 3-Ele-portable Yagi with aluminium tubes as a leightweight antenna. Details see in the pictures below.

For each band he has an own 2x75-Ohm-quarterwave matching cable.

Insulated middle part of the radiator:

The middle part of the director:

All parts ready for assembling: