Blue Flower

40m + 80m Vertical Antenna

 

 

This is a easy to build Lowband Vertical Antenna. For the design and further info's watch DG9MDM's homepage. I got the info's from there.

At first i built a 1:1 Balun for the feedpoint (H2007 Cable and a Amidon FT240-43 Core in a weatherproof box)

Then i made a 40m Trap out of coax cable (instructions how to do it could be find easily in the internet). I used H2007 for the trap, it worked fine and i took 750 Watts on it, no problem with heating or SWR.

Then i used a 15m GFK Mast (from dx wire) to mount the wire (F-Litze, also from dx wire) on it. At first 10m, then the trap, and then 5-6m (you could cut a little bit to change the 80m resonance point) wire going to the top of the mast.

At the ground i put the feeding box (1:1 balun) on a wooden pole and mounted the Radials on it. I used 7x 10m cooper wire. I also tested adding 3x 20m additionally, but made no effect on 40 and 80m. I grounded the feedpoint with another 1m 16mm cooper wire split up and thrown under the gras. It made the SWR 0.2 parts better.

It's not easy to put a 15m Mast in the air. So you need a second helper (or do it alone like me, but i don't recommend that but it's possible). You also need to put a mounting point for guy wires in ca. 8-10m height. Without guying the antenna on 1 or 2 points with 4 wires in different directions, your antenna will fall down in the first light wind. My antenna survived 90 km/h without any problem during the CQWW weekend in October 2013.

The SWR on 40m was fine, it covered the whole ssb part with over 150 khz and above 7.2MHz. On 80m you could get ca. 120 khz bandwith. So choose ssb or cw. Or use a good tuner and don't cut wires :-). I used the antenna without any tuner (only below 3.650 MHz with the build-in tuner, or matched with the PA).

It is not a perfect antenna - a good radial network would bring another few DX contacts. I made my first 40m contacts to VK and ZL with 5/9 and 5/9+10 and my first JA contacts on 80m (don't ask for the signal, but i got 4 JAs in the log in 3minutes).

When i compare my Vertical to the 40m Rotary Dipole, the Vertical clearly looses. When comparing to the 80m Inverted V Dipole, the Dipole win's in all EU contacts. But when trying to get DX, you could get 6-9 dB, sometimes a bit more, on the vertical on 80m. So i got some contacts i couldn't read on the dipole.

Lowband DXing is not my speciality, but this lightweight and cheap antenna (costs you only ca. 150€) is a very fine one. I had a HF2V and a Gap Voyager in my garden - both are nice antennas, but the performance is not better than this antenna. So safe the money and build your own antenna :-)