Antennas come in a bunch of different shapes and sizes, but they’re all designed for the same purpose – to pick up a very specific radio wave frequency. You’ll find antennas ranging from the long metal wires sticking out from an FM radio to something rounder like a satellite dish, or even a tightly tune piece of copper on a PCB. In a transmitter, antennas are used to send radio waves, and in receivers, they’ll be used to pick up on a radio frequency. Antennas all have three distinct features that they’re measured by, including:

* Direction. For some antenna types, such as a dipole, the antenna has to be mounted in the proper direction, facing the direction of the radio wave transmission. Some antenna types, like those found in an FM radio, don’t need to be oriented in a specific direction and can capture radio wave signals from any angle.

* Gain. The gain of an antenna describes how much it is going to boost a signal. For example, if you turn on an old analog TV, then you’ll still likely get a picture, just a fuzzy one. This is because of the metal case and components in the TV act as an antenna. But plug an actual directional antenna in, and you’ll be able to boost the signal, and gain a better picture. The bigger the gain, measured in decibels (dB), the better the reception you’ll get.

* Bandwidth. Last, an antenna’s bandwidth is its particular range of useful frequencies. The higher the bandwidth, the more radio waves that it can pick up. This is ideal for televisions as it allows them to get more channels. But for things like your smartphone which only need a specific radio wave, a full bandwidth isn’t as necessary.