The art of building simple antennas.
Most of us HAM's don't have the possibility to erect the type of antenna we encounter in our nicest dreams. In daily life, there are restrictions in height and horizontal size. But with some inventiveness, it is possible to build decently performing antennas which will let you work the HF amateur bands with great pleasure. As a rule of thumb, try to install a dipole or inverted-V antenna with an open-line feeder which can cover a large number of bands. Install as much of wire length as possible, even if this means you will have to bend the ends in a funny way to keep them within your garden or roof area. In my case, I managed to hang out an inverted-V antenna with 2 x 18 meters of wire. As can be seen in the top view and side view drawing of the house and garden, the antenna is in fact an inverted-double-V type. there is a V in the horizontal plane and also one in the vertical plane. The central mast of the antenna is made of 6 ex-military stackable poles, each 1.20 m in length. Located on the balcony, the height of the antenna top is 10 m. Two sub masts of 4 poles are tied to the garden fence. The two dipole wires are running from the central mast to the two sub masts, are bending backwards from there and are terminated on an insulator from which a nylon rope supports the wire and keeps it in the air. Despite the funny shape of the antenna the performance is not bad at all. With 5 Watts of QRP power I worked all continents in digi mode. In the beginning I only used 2 x 10 m of wire. That gave good results on the bands from 40 m tot 10 m. But I loved to also work on 80m. And with the extra 2 x 8 m of wire, I can also work on 80 m and even 160 m can be used with reduced efficiency. The picture of the central mast shows the junction box in which the dipole halves are connected to de 450 Ohm ladder line. Through this feeder line, a nylon rope is woven to give extra support for the mast and to prevent it to bend forward due to the tension of the dipole halves running to the sub masts.
As can be seen in the close-up, the support of the center part of the antenna is made of Perspex. A little plastic box is used for the connections of the dipole halves to feeder. Perspex parts and the junction box are bolted to a short piece of aluminium tubing that fits into the top of the highest pole.
The photograph of the whole antenna gives an impression what the antenna looks like in real life. So the whole thing is a bit odd but the antenna has the required length to work properly on 80 m and upwards. Radiation efficiency will not be as good as a "straight" inverted-V antenna due to the backfolding but the results are quite encouraging, even with 5W of QRP power in digimode. The impedance seen at the feeder end will vary widely between different bands. But the symmetrical tuner will handle that smoothly. And high SWR ratios on the 450 Ohms ladder line will not give high losses as would be the case with coaxial cable. Mechanically, the antenna construction is a bit fragile. I don't keep it up on a permanent basis. When a severe storm is anticipated, I will dismantle it within 20 minutes. And building up it agian can be done in the same timespan. And if you think: I don't have the room for such an antenna, just look at the picture with the 2 x 4 m open dipole, also fed with the 450 Ohm feeder. With this antenna, the 20, 17, 15, 12 and 10 m bands can be covered. Even 30 m is possible with reduced efficiency. The antenna is made of aluminium tubing of 20, 15 and 12 mm thickness, the dipole halves supported by a piece of perspex material and bolted to the stackable ex-military masts. So the conclusion is: don't be afraid to experiment with antennas and dare to twist and bend them until they fit in the space available for them. Even if you can't use an outdoor antenna, just look what's possible under the roof top. Use the length of the house and let the ends bend downwards. In most cases, you can hang out 2 x 7 m at least that will let you work on all bands between 30 and 10 m. I hope I have given you some ideas and have encouraged you to make the most of it when budget and antenna space is limited.