40m quarter wave vertical

Late in 2008 I decided to build a full sized quarter wave vertical aerial with the idea of testing its performance for working DX during the winter months. As always with my aerial projects, little attention was paid to making the construction of a permanent nature - I experiment with aerials all the time and nothing that I build is intended to stay up for more than a few months. If you want to try building this aerial and plan for it to be a permanent installation then you will need to re-engineer some of the constructional aspects to make them more robust. Here is how it was built:

Full view Top Base Feedpoint

The vertical radiator was made from single core electrical wire of the type used in house wiring. This wire was taped along the length of a 10m fishing pole that had been bought for 15 GB pounds at a radio rally. I fixed the vertical radiator wire to the pole at intervals of about 1m along the full 10m length of the pole. The pole is very light and easy to handle, so it's ideal for quick experimental construction. I'm not sure what material the pole is made from - but I have assumed that it is not conductive. The sections of the pole pull out from within each other to extend to the full 10m and at each joint the inner section becomes a friction fit against it's partner outer section. I though this was a bit too flimsy even for a short term installation so I wound a few turns of PVC insulation tape around each joint to make them slightly more secure. You can see the yellow coloured radiator wire in the photos.

If you look at the Full View and the Top you will see that I used 2 sets of 4 guy ropes. I prefer using 4 guy systems rather than 3 because it's normally not much more difficult to do and it makes the installation stronger and also much easier to raise and lower in a controlled fashion. The guy rope was just some lightweight general purpose stuff I had lying around. The 2 sets of guys were fixed to the pole at about 4m and 8m up. Four heavy duty tent pegs were used as the guy anchors and they were placed at about 3m out from the base of the pole.

Looking at the Base you will see that the pole sits on a wooden plate to prevent it from sinking into the ground. The upside-down blue pot is the improvised weatherproofing for the feedpoint and is just an old plant pot (NOT one with a drainage hole in the bottom!).

Lifting the pot lets us see the Feedpoint details. A piece of heavy duty electrical connector block was used as the main part of the feedpoint. The yellow radiator cable goes to the top connector terminal as does the centre core of the coaxial cable. The other 2 connector terminals are shorted together to form the ground connection where the 3 radials and the outer of the coaxial cable get connected. The 3 radials are about 10m long and were spread out as best I could in the space I have in my garden.

The aerial turned out to be resonant at just below 7.000 MHz and only one length reduction of about 20cm was required to bring it onto the lower part of 40m where I wanted it to be for CW DXing.

As far as performance is concerned, there is no doubt that this vertical performs better for working DX than the 40m dipole at 8m that I used as a comparitive reference. There are times when the RX noise level on the vertical is higher than on the dipole and then the dipole is then better on RX. During the testing period (winter 2008/9) there has only been relatively long skip propagation on 40m so no comments can be made about the preformance of the vertical for more local working (in my case that means within the UK).

During the 2008 CQWW CW contest I used the vertical for a 100W single-band 40m entry and managed to work 87 countries and 20 zones. That was enough to let me take the GM record score for this section of CQWW CW.

73 de Barry GM3YEH