One antenna that many amateurs are having success with is the off-center-fed (OCF) dipole. The length of the OCF dipole is approximately the same as the standard dipole, as shown in Figure 1 below. Unlike the standard dipole, however, the OCF dipole has its feedpoint approximately 1/3 of the way from one of the ends. Unlike the standard dipole, its elements are not equal in length. One is approximately 1/6 of a wavelength, while the other is approximately 1/3 wavelength.
At the feedpoint, the impedance of an OCF dipole is approximately 200 ohms. So, in order to use 50-ohm coax to connect the antenna to our radio, we use a 4:1 balun, instead of a simple insulator, at the feed point. This balun transforms the 200-ohm feedpoint impedance of the antenna to 50 ohms.
The magic of the OCF dipole is that the feedpoint impedance is about 200 ohms, not only for its primary band, but also on all harmonic frequencies. This means that an OCF dipole cut for 80m, will also be a good match on 40m, 20m, and 10m. The internal tuner in most radios should easily tune this antenna on those bands, and it is useable on the other HF bands with an external tuner.
While it’s relatively simple to build one of these antennas yourself, there are antenna kits on the market that simplify the task of gathering up all of the parts you’ll need. AmateurRadioSupplies.Com sells the W8AMZ OCF Dipole Kits. The kit includes a 4:1 balun, end insulators and the wire you need to build the antenna. The wire is a high-quality, black-jacketed #14 gauge stranded copper wire. The center insulator and end insulators are high quality PVC and are UV stable. The antenna is rated at 2 kW.
As with all multi-band antennas, there are some compromises, but for many amateurs the benefits outweigh the disadvantages. If you like experimenting with antennas, I encourage you to give it a try.