Freeview reception - all about aerials

Your ability to receive all the Freeview transmissions depends on the suitability of aerial: the design style, "group" and its physical location.

^{Published on 19th December 2005 at 18:47 by Brian Butterworth on UK Free TV}

Your ability of receive all the Freeview transmissions depends on the suitability of aerial

• the design style,
• the "group", and
• its physical location.

Standard type - Yagi aerial

The standard type of TV aerial is known as the Yagi aerial. It is mounted on a pole, and consists of a rod with a reflector (shown green) at the back and many spiky elements (in grey) at the front. The connecting cable connects to the element nearest the reflector, known as the driver (shown in blue).

These Yagi aerials are directional and so pick up signals best from a transmitter that the rod points towards. The more elements the aerial has, the better it picks up a signal and becomes more directional.

A standard-type aerial is all that is required for analogue TV reception in most places. These antennae have between 10 and 18 elements and a single reflector. These are not recommended for new installations for good digital television reception, but will more often than not function perfectly in good reception areas.

Typically these aerials are designed to receive only some transmission frequencies - see "groups" below.

Digital High Gain

These aerials are designed for poor digital reception areas, and have two reflectors. For maximum signal strength, some digital high gain aerials have up to 100 elements. A more expensive aerial is only required where the signal strength is low, but can often provide Freeview reception where it might otherwise be impossible.

The CAI (that represents aerial installers) has four standards for digital TV aerials. The highest standard "1" is for homes on the fringes of coverage areas, intermediate standard "2" is suitable for use within the coverage area; minimum standard "3" is for good coverage conditions. These aerials can be either wideband, or receive only selected frequencies - see "groups" below.

Grid

Grid aerials have been used to improve analogue reception in poor reception areas. They are generally unsuitable for Freeview reception, however some installations may work. Otherwise replace with a digital high gain Yagi aerial.

Indoor

Indoor aerials are generally not suitable for Freeview reception. In areas of good signal strength it is often possible to receive some transmissions.

Loft mounted

Loft mounted arrivals are not generally recommended for Freeview reception, as the roof tiles and plumbing will degrade the signal. Some compensation for this loss of signal can be made by using satellite-grade cable to connect the set top box to the aerial.

Positioning

The best position for a TV aerial is mounted outdoors, as high from the ground as possible, pointing directly at the transmitter. The signal can be blocked by hills and tall buildings. It should be positioned away from any other aerials.

Horizontal or vertical?

The transmitter will either use vertical mode which requires the elements of your aerial to be up-down, or horizontal mode which requires them to be level with the ground.

Groups

Both analogue and digital television is transmitted the same group of transmission frequencies (known as channel 21 through to 68). A coloured marking on the aerial shows the group.



To create the best possible analogue picture, TV transmissions from adjacent transmitters have been designated to several different groups of frequencies. By using an aerial that receives only the channels in the correct group, the analogue picture can be kept free from interference.

To receive Freeview transmissions from the same transmitter it has been sometimes necessary to use frequencies that are not part of the transmitter's normal group. When this has occurred, the aerial will need to be replaced with a "wideband" aerial (also known as group W) - one that covers every group.