Dipole antennas are some of the simplest antennas to build in addition to being very efficient and solid performers. I wanted to make a simple dipole antenna for QRP portable operation that could be used on multiple bands. I also wanted it to be light enough to be supported by my light-duty 31 ft Jackite mast in an inverted V configuration.
Link dipoles are a great way to make a lightweight multi-band antenna because you only have one run of wire (vs a fan dipole), there are no traps or coils, and you don’t need a complicated and heavy balun (vs an off-center-fed dipole). Band selection is achieved by connecting or disconnecting the appropriate links to make the antenna as long or short as needed to work on the band you want. To keep the antenna as light as possible I used 26 AWG insulated stranded copper-weld wire from The Wireman (#534). This wire is small, but because it has a steel core it is stronger than pure copper wire would be. It also has very tough insulation that protects the wire very well and is exceedingly lightweight (1000 ft weighs under 1 lb, and I am only using about 66 ft).
For the physical links in the dipole I used Nite Ize MicroLock S-Biners. These are small polycarbonate double-carabiners that are more than strong enough and very light. I made a loop at each end of every antenna section and secured it using adhesive lined heatshrink tubing. While not the strongest connection this should be adequate for this application since the antenna is so light that there isn’t much strain on any one point. The electrical links in the dipole were made using Anderson Powerpoles. The antenna itself was cut for the 20, 30, and 40 meter bands. I am considering adding an 80 meter section in the future, but that may add too much weight.
The center feed-point was made using a small piece of 1/8″ acrylic. This was drilled for antenna wire strain relief as well as #8 bolts for the connection between the antenna and the coaxial feedline. I decided to forego using a 1:1 balun at the feed-point to save weight. The feed assembly is secured to the mast using wire ties. Since every mast section is tapered the assembly can only slide so far down from the top before it fits tightly to the mast. I adjusted the wire ties to place the peak a couple of feet down from the top where the mast is somewhat more substantial and can more easily support the weight of the antenna. For coax I have been using RG-58, again to keep the weight down. I may end up moving to RG-8X in the future if the mast can support it since it is much lower loss.
A handy feature of this antenna is how easy it is to put up. The mast is a good match for my car’s flag pole hitch mount (using a 2″ PVC spacer) and is strong enough to be freestanding. To erect the antenna I just have to secure the upper three sections of mast (the sections friction lock together), place the mast in the mount on my car, unroll the antenna, slide the feed-point onto the mast, connect the coax, push the rest of the mast up, and spread out & secure the antenna ends. I can be on the air in about 5 minutes.
All of my efforts to keep the antenna as light as possible definitely paid off. Together the antenna and winder weigh only 15 oz (not including feedline). This makes it a perfect match for the lightweight mast and a small QRP radio. I look forward to getting a lot of use out of this setup.