The digital television set is now a standard fixture in many homes. Most areas are able to receive dozens of free channels through Free View. However, it is often necessary to fit a special arial on the roof to get the new digital services. Depending on the area in which you live, there is a range of aerials to cope with the quality of reception — and various devices that enable you to enjoy your favourite programmes anywhere in the home.
There are three normal positions for a television aerial: on the roof, in the loft or placed on top of the set or elsewhere in the room. A roof fitting, sited as high as possible, is the most satisfactory method, although this job is probably best left to a professional. You can keep down the bill by laying the special coaxial cable yourself and getting the rigger to connect up after he has completed the installation on the roof.
An aerial on top of the set is only really satisfactory where there is outstanding reception, whereas an aerial in the loft can provide excellent viewing, if you are not too far away from one of the broadcasting authorities’ transmitters.
If you move into a new area and notice few rooftop installations, you can usually assume the area has good reception. It may mean there is no reception, so check with the BBC and IBA engineering information services and see a local dealer. He usually will not mind you doing the job yourself because, like some television rental companies, he probably contracts his aerial work out to someone else anyway.
Television aerial installations are becoming more sophisticated and, by using a combination of the most sensitive roof aerial and masthead amplifiers, you can pick up distant TV stations.
Use low-loss coaxial cable to connect the aerial t’o the set. This is expensive to buy and you should take the shortest possible route when you lay it, not only for economy’s sake but because a short run helps to maintain the signal’s strength. The cable consists of an outer insulating sheath, a metal screening braid (which stops unwanted signals being picked up), an inner insulating sleeve and a final inner wire which actually carries the signal. Avoid bending , it sharply as this can seriously affect reception.
You can run the cable in plastic conduit, bury it in plaster or fix it to your walls with cable clips. In some modern homes you may be able to run it from the roof or loft, through the roof space and down the cavity in your walls to an aerial socket outlet (which can be either flush or surface-mounted) or direct to the plug which connects at the back of the television set.
If you run the cable externally, either from a roof aerial or through the eaves in the case of a loft aerial, you must check it periodically to see whether it is being chafed by the wind rubbing it against roof tiles or brickwork. If you bury it, you cannot take the aerial with you when you move; this need not be particularly inconvenient, since when moving from one area of the country to another, you may well need a different aerial because different channels are used in different areas and signal strengths vary considerably. So it is as well to include the aerial in the fixtures and fittings when you sell.
When wiring the cable either to the plug or in the weatherproof junction box on the aerial, remove 38mm (1 fin) of outer insulation and loosen and fold back the braid to leave about 20mm (tin) of inner insulation clear; then remove 6-13mm (*-fin) of the inner insulation from the braid.
The cable is fed through an access hole (and protected by a grommet) at the junction box, the inner wire connected to the terminal and the braid clamped down with a metal clamp. The junction box is generally covered with a clip-on PVC cover,
When wiring up the ‘plug, slip on the plug collar and the braid clamp, tighten the screw on the clamp, thread the inner wire into the pin unit and screw the collar onto the plug body. Unless the screening braid is properly clamped it will not do its job effectively.
Fixing the aerial
The aerial should now be screwed into the highest possible point in your loft and as far away from galvanized steel water tanks as possible, since the metal may deflect the signal. When you have done this, point the aerial so the shortest element or cross piece is nearest to the transmitter and, by trial and error, establish the best position (by going down to the set to check the pictures on the different channels or getting someone else to look for you) before bolting the aerial into its optimum position. Your dealer should have sold you the appropriate UHF aerial for your district and this may have from five to up to 21 elements (or cross pieces).
If your signal is particularly weak and needs boosting, you will have to install an amplifier close to the aerial. A number of manufacturers produce these and in the case of a roof aerial the fitting should be left to the rigger. If you are fitting one to your loft aerial, you will need an amplifier and accompanying power unit. The amplifier is bolted to the aerial masthead and the coaxial cable enters and leaves this (the method of connection depending on the type of amplifier), runs into and out of the power unit and then into the set in the normal way. The power unit, which should be connected to a fused connection unit with 2.5sq mm twin core and earth cable, contains a transformer which sends 18 or 24 volts output into the amplifier along the coaxial down cable. — –
An amplifier will not alter the quality of the signal, only its strength, and may exaggerate any faults caused by an inadequate aerial.
Aerial sockets The neatest way of connecting your aerial to the set is via a specially designed aerial socket, which eliminates trailing cable across the floor. These are connected in the way described for the aerial junction box. You will. Of course, need another length of cable and two plugs to connect from the socket to the set. Sockets are available which also provide a connection for your FM radio (from a separate VHF aerial).
Fitting an extra outlet
If you wish to run a second set off the same aerial but in another room, you will need a splitter unit; this can be fixed to a skirting board with countersunk screws. Generally this has a socket outlet for the set in the same room and the usual terminal and braid clamp for the cable from the aerial and for the cable that carries the signal to a second set elsewhere in the house. Adding an extra socket may reduce picture quality in areas where the reception is already below par.
Another method is to use a combined splitter-amplifier which contains its own power unit and is connected to the mains, via a fused connection unit, using 2,5sq mm twin core and earth cable. This has an input coaxial socket to take the cable from the aerial and up to four output sockets for sets in different parts of the house.
The cable connector is a simple device that enables you to extend existing cable. It has female sockets at both ends and these take the standard coaxial plug. Again it will further diminish the quality of the picture if you are already suffering from a poor signal.