01

How an aerial works

Television signals are transmitted from a broadcast tower as radio waves at specific frequencies. An aerial is designed to resonate with these frequencies and convert the incoming radio waves into a small electrical signal. That signal travels down a coaxial cable to a tuner, which decodes it into the picture and sound you see on screen.

The strength and clarity of the signal an aerial receives depend on several factors: the distance from the broadcast tower, the terrain between the tower and the aerial, the height and orientation of the aerial, and any obstructions such as buildings, hills or trees. This is why two households in the same neighbourhood can sometimes experience very different reception quality.

02

Digital terrestrial television

Most countries, including South Africa, have moved or are moving from analogue to digital terrestrial television (DTT). Digital signals are more efficient than analogue ones: they allow more channels to be broadcast in the same amount of spectrum and generally produce a cleaner picture, free of the static and ghosting that affected older analogue broadcasts.

To receive digital terrestrial channels, a household typically needs a suitable aerial, a length of coaxial cable in good condition, and either a television with a built-in digital tuner or a separate set-top box that decodes the digital signal for an older television. The aerial itself does not need to be digital; what matters is whether it is suited to the frequency band used by local digital broadcasts.

03

Outdoor versus indoor aerials

Outdoor aerials are mounted on a roof, chimney or mast, well above obstructions, and generally provide the strongest and most reliable signal. They are more exposed to weather, so they need to be properly weatherproofed and securely fixed.

Indoor aerials are easier to install and move, making them a popular choice for renters or for secondary television sets. They work best in areas with a strong broadcast signal and few obstructions, such as flats on higher floors or homes located close to a transmission tower. In areas with weaker signal, an indoor aerial may struggle to deliver a stable picture, even with a built-in amplifier.

04

Choosing the right aerial

There is no single aerial that suits every location. The right choice depends on:

• Distance from the nearest broadcast tower
• Whether the signal path is direct or obstructed by hills, trees or buildings
• The number of television points in the home that need to be fed from one aerial
• Local weather conditions, which affect how robust the mounting and cabling need to be

Because reception can vary significantly even within a small area, it is often useful to consult official broadcast coverage maps, where available, before deciding on an aerial type and installation height.

05

Cabling and signal loss

Even the best aerial will underperform if the cabling between it and the television is damaged, too long, or of poor quality. Coaxial cable degrades signal strength over distance, and every connector, splitter or joint in the cable run introduces additional loss. For installations where the aerial feeds multiple television points, a signal amplifier (sometimes called a booster) can help compensate for this loss, but amplifying an already weak or noisy signal will not improve picture quality and can sometimes make interference worse.

06

Why reception problems happen

Picture breakup, pixelation, or a complete loss of channels are usually caused by a change in the signal path or in the equipment itself. Common causes include aerial movement after storms or strong wind, corrosion in outdoor connectors, cable damage from rodents or weathering, and interference from other electronic equipment. Because digital signals either work cleanly or not at all, a weakening digital signal tends to show up as blocky pixelation and dropouts rather than the gradual fuzziness associated with analogue reception.

This site is intended as an independent, general reference for anyone trying to understand how television aerials work, what types exist and how to approach common reception issues. The following sections look in more detail at the different types of aerials available and at practical troubleshooting steps for common reception problems.