Guide to Antennas

Antennas are probably the simplest part of any form of radio reception or transmission device and yet are also its most vital – without them, there’s no way of intercepting or sending radio signals. Modern antennas crop up in all sorts of applications, and they are all optimised for specific frequency ranges, but the basic technology dates to the late nineteenth century.

Back in the pioneering days, antennas were used to prove that electromagnetic waves existed, by one Heinrich Hertz, the German scientist whose name is now used as the unit of frequency in waves (1000 Hz is 1000 cycles per second). The generation of radio waves for practical use came in the late 1800s and early 1900s, thanks to Guglielmo Marconi. He experimented with different shapes and sizes of antennae and gradually moved them further from the transmitter, until in 1902 he managed to send a signal across the Atlantic from Cornwall to an antenna in Newfoundland, Canada.

Antennas are essentially just electrical conductors that are connected to a transmitter or a receiver. By conductor, that just means a piece of metal, often copper or aluminium. In use, they can look like quite chunky pieces of plastic, but the plastic is there for three reasons: to support potentially very thin wire and keep it straight; to protect the wire from physical damage (bending and snapping) and to stop corrosion. Many antennas have no such coverage, such as telescopic radio aerials or TV aerials.

Radio waves occupy the space in the electromagnetic spectrum with frequencies roughly between 10 kHz (10,000 Hz) and 100 GHz (100,000,000 Hz). For example, FM radio has a frequency range of 87.5 MHz to 108.0 MHz, while Wi-Fi is transmitted and received at 900 MHz, 2.4 GHz and 3.65 GHz.

The job of the receiving antenna is to “listen” to the radio wave frequency that it has been calibrated to by the tuner, and the transmitting antenna sends out signals at the frequency it determines. That’s how there can be thousands of different radio, TV, Wi-Fi, Bluetooth, 4G and other radio signals flying through the air at any given time, but the radio only picks up one signal.

Different antennas are designed for a host of purposes. In general (but not necessarily), the closer an antenna must be to the source of the electromagnetic waves, the smaller it can be. It’s why a traditional TV aerial is more than a metre in length and sits on the top of a building where it can “see” the transmitter on a faraway hilltop, but an RFID antenna is tiny but can communicate with another device as long as they are almost touching. Let’s look at some of the various types.

As you can see, antennas are much more than a little stick that pokes out of a radio. They’re precision manufactured to achieve optimum performance over specific (or multiple) bands, and although the technology is old, it is forever improving. If you know what kind of antenna you’re looking for, find the right radio antenna here.