I have built a multi-band DIY fan-dipole antenna for 40-meter, 20-meter, and 15-meter HF bands. A fan dipole consists of several dipoles fed at a common feed point, through an optional 1:1 balun. I have tested this antenna and I have confirmed QSOs from Philippines to Brazil (other side of the world from the Philippines, via FT8 on 15 meters) and Philippines to Sydney, Australia (SSB voice on 15 meters).
A fan dipole may be designed to operate on a number of bands simply by adding new elements to an already existing dipole, but adding new elements may change the tuning of the already tuned dipoles, making it difficult to build one that is designed to operate on too many bands. In this particular antenna build, I combined three dipoles—for 40 meters, 20 meters, and 15 meters—to form a multi-band fan dipole on a single feedline.
The driven elements are 12-gauge insulated wires, center-fed (split in the middle). I used a 7 meter RG8 coaxial cable feedline with 1:1 BU-50 balun. The feed point is housed in a weatherproof metal enclosure that has been placed on an elevated concrete ledge. I used non-metallic material to raise and anchor the ends of the wires, such as nylon rope.
The 40 meter band has 10 meters of wire on each sides (total of 20 meters both sides), the 20 meter band has 5 meters of wire on each side (total of 10 meters), while the 15 meter band has 3.38 meters of wire on each side (total of 6.77 meters). Adjust the lengths of the elements for lowest SWR on the desired operating frequency. Since there is likely interaction between the elements, always check the tuning of all the other bands when tuning the antenna for a specific band.
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Night Sky in Focus | Astronomy and Amateur Radio © Anthony Urbano | Manila, Philippines