Construction  12-Ele.-28-Ohm 13-Ele.-28-Ohm 14-Ele-28-Ohm 16-Ele.-28-Ohm
17-Ele.-28-Ohm 19-Ele.-28-Ohm 21-Ele.-28-Ohm 23-Ele.-28-Ohm 27-Ele.-28-Ohm

70cm-Longyagis in 28Ohm-DK7ZB-Design

Short Datas of the Yagis at 432MHz

Type

12-El.

13-El.

14-El.

16-El.

17-El.

19-El.

21-El.

23-El. 27-El.

Boom

2,50m

3,00m

3,10m

3,88m

4,05m

4,65m

5,25m

5,70m 7,05m

Gain

13,8dBd

14,5dBd

14,6dBd

15,5dBd

15,65dBd

16,2dBd

16,6dBd

17,0dBd 17,7dBd

All Yagis in 28-Ohm-Technology, elements mounted with polyamid-clamps (Konni) or similar and 10, 8  or  6mm Diameter. Electrical details on the pages you see above, plots with "YO" from K6STI and "EZNEC +4"  from W7EL

The elements have 10mm, 8mm or 6mm diameter, because this is very uncritical and you get  the expected datas! For the tuning let the radiator 2mm longer and cut for best SWR at 432MHz. If the minimum is worse than 1.3 you should try to change the place of D1 +/-5mm. If you have a spectrum analyzer you can follow that rule: Making D1 shorter raises the resistance of the radiator, making it longer the resistance will drop down. Greater changes in the length of D1 as +/- 1mm will cause another radiator length!

I have redesigned some Yagis (12/2003) with "EZNEC4+", because the "cut-off"-frequency was very close to 433MHz, now the antennas have 0,05-0,1dB less gain, but the design is not so critical and the bandwidth is greater.

The picture of DK1IP shows the 19-El.-Yagi reflection coefficient at 432,2MHz (marker) and the design principles mentioned above.

Very important: Matching cables should be exact symmetrically between the two radiator parts!

Radiator with the 2x75-Ohm-coax-cable (PTFE)) in the box with the N-socket for the DK7ZB-match.

Here with the 12mm-Radiator built by Wolf, DK1IP

Mounting of elements

With these clamps the 8mm-elements are mounted isolated 2-3mm above the boom. The screw has 3mm and is stainless steel. The screw and the electrical contact to the boom has no influence to the length of the element.

The parallel 75-Ohm-Cables for the DK7ZB-Match (see other Webpage!)

Length lambda/4*V

V=Velocity of propagation

e.g. for Full-PE (RG-59) V= 0,667

Foam-PE V=0,81-0,85,   PTFE V= 0,71

 

Use a good cable with a good braid for high screening effectiveness!

The Reflector, Radiator and Director 1 with the mounting box. The cable must be mounted symmetrically!

Assembling of the elements for a 4x23-Element-Group at OL6R

The Radiator-Box for a 23-Ele. at OL6R