The 2 element (28 Ohm) DK7ZB antenna (0,60m boom) 50 MHz band

 

Fig.1 - The antenna at midnight beaming east (UT, YO)

This is my 50MHz antenna. The project and the calculations have been done by Martin DK7ZB (www.qsl.net/dk7zb).

This kind of antenna has a good gain: I have measured it by a comparison with a vertical GP. The result was 3dB better for the Yagi, but BE AWARE of this calculations!!!

For further informations about the calculations and the simulations, please refer to the original website.

In this webpage I will illustrate only what I have done. So you can take ideas, as I did from original website.

Following, I have chosen the most important photos for explaining my project.

THANK YOU VERY MUCH, MARTIN!

PS: sorry for my poor English.

Sorry, but I don't have photos of single pieces before building it.

1. Take a ABS (or plastics) box for home electrical circuits

2. Choose the right piece of Aluminium for the dipole (I have chosen 12mm)

3. Find a piece of plastics that is used for electrical insulations between the two parts of the dipole (as seen in the original website)

4. Do 4 holes into the box: one for PL connector (left-bottom of the photo), one for the balun (right.-up), two for the dipole pieces.

5. You can see that I have done some marks with a pen onto the insulation piece for the dipole. I needed this marks also for doing the right holes for a better soldering of the cable.

Fig.2 - A particular of the link between the dipole and the balun.

Fig.3 - The balun and the dipole box finished.

6. The box is finished. Every word is pointless.

7. For better stability I put two screws near the box holes (you can one of these on top of the photo).

8. The balun is built with a 75 Ohm TV cable, as seen on dk7zb's website.

9. You can choose to cut a longer piece of Alu 20x20 for better allocation of the balun.

I don't found any problem with it. This modify moves the center of mass near to dipole, so it was simple for me to put on the mast.

Fig.4 - The balun in the right position.

Fig.4

10. This is the junction between the boom and the mast.

11. I put the antenna on a mast of 3,5m starting about 1m from my terrace. So the antenna is high about 1,5m over the roof.

12. I'm turning manually the antenna, because it has a principal lobe very large. The simulator shows about 60 degrees of angle at -3dB. My test reflects this statement.

Last big test has done in the IARU Reg.1 50MHz contest: with a quite good tropo on the Saturday, I can do qsos up to 150Km very well (signals strong), up to 250Km (signals readable), maximum is 350Km with difficult. In the Sporadic-E opening on Sunday, I had a 3 hours pileup with all Europe in the same time (from UT to EA).

I recommend this antenna to all people that now use a dipole for the Magic band, because it has a little gain, good for: tropo, Sporadic-E, Meteor Scatter and F2 (wkd 3 USA stns last summer).

Fig.5 - The antenna finished that wait to be put on the mast.

 

I hope to be clear in explaining and I hope also to have been undestood, despite my poor English.

73 from Costy IC8TEM