The vertical is a popular antenna among hams who lack the space for a beam or long wire antennas. In an electrical sense, a vertical is a dipole with half of its length buried in the ground or “mirrored” in its counterpoise system. Verticals are commonly installed at ground level, although you can also place a vertical on the roof of a building.
At first glance, a vertical looks like little more than a metal pole jutting skyward. A single-band vertical may be exactly that! However, if you look closer you’ll find a network of wires snaking away in all directions from the base of the antenna. In many instances, the wires are buried a few inches beneath the soil. These are the vertical’s radials. They provide the essential ground connection that creates the “other half” of the antenna. Multiband verticals use several traps or similar circuits to electrically change the length of the antenna according to the frequency of the transmitted signal. (The traps are in the vertical elements, not the radials.)
Vertical antennas take little horizontal space, but they can be quite tall. Most are at least 1/4-wavelength long at the lowest frequency. To put this in perspective, an 80-meter full-sized vertical can be over 60 feet tall! Then there is the space required by all those radial wires. You don’t have to run the radials in straight lines. In fact, you don’t even have to run them underground. But you do need to install as many radials as possible for each band on which the antenna operates. Depending on the type of soil in your area, you may get away with a dozen radials, or you may have to install as many as 100.
Contemplate spending several days on your hands and knees pushing radial wires beneath the sod. It isn’t a pretty picture, is it? That’s why several antenna manufacturers developed verticals that do not use radials at all. The most efficient of these verticals are actually vertical dipoles. Yes, they are dipole antennas stood on end! There is no reason why this cannot be done. In fact, a vertical dipole can work quite well.
So how does a traditional vertical antenna stack up against a traditional horizontal dipole when it comes to performance? If you have a generous radial system, the vertical can do at least as well as a dipole in many circumstances. Some claim that the vertical has a special advantage for DXing because it sends the RF away at a low angle to the horizon. Low radiation angles often mean longer paths as the signal bends through the ionosphere.
Without a decent radial system, however, the vertical is a poor cousin to the dipole. The old joke, “A vertical radiates equally poorly in all directions,” often applies when the ground connection is lacking, such as when the soil conductivity is poor. If you can’t lay down a spider web of radials, dipoles are often better choices.