Monopole, dipole, or bowtie?

If you’re thinking about an antenna, there really are only a few different kinds. Do you know what they are?

The antenna above is a monopole. In essence, it’s one big piece of metal. It’s the simplest form of antenna, which is why it’s used on small radios and televisions. It’s also used on cell phones and satellite receivers as well. The monopole is all around us… in the form of radio and television towers.

The basic principle of a monopole is simple. It captures radio waves and relies on basic physics to do its job. It’s omnidirectional, meaning that it picks up in all directions. It either uses the actual ground (you know, dirt) to ground itself or relies on some simple grounding within the device. It is compact and can be made flexible or can collapse in on itself in the case of the picture above.

A dipole is a little more complicated. The most common dipole is the “rabbit ears” antenna, although the common Yagi antenna is actually nothing more than a series of dipoles. The dipole antenna uses two conductors and is a little more specialized. The length of the dipole determines the frequency that it picks up best. All dipoles work best when they’re perpendicular, like the image shown above. When you use rabbit ears, adjusting the tilt of the elements is actually adjusting the wavelength you receive best by changing the horizontal size of the antenna.

In the case of outdoor antennas, several dipoles of different sizes are used, along with reflectors to make sure they don’t interfere with each other. In this way, your outdoor antenna can receive all the frequencies it needs.

The bowtie antenna is a specialized form of dipole antenna that is used for picking up UHF signals. While VHF signals respond better to the traditional dipole shape, UHF antennas respond better to large elements that take up both horizontal and vertical shapes. That is why UHF antennas will sometimes be round, as in the case of the Antennas Direct Clearstream series, and are very often “bowties” or “cat’s whiskers”. This shape does a better job of picking up the very different size waves used for UHF broadcasting.