30 June 2023 tbs.pm/78958

Special pull-out supplement to the Radio Times, published 24 January 1958

Interference on the medium waves fills the air with strange noises; on VHF reception is clear and true

WHAT IS VHF? It is a new and better way of broadcasting sound programmes – that is, of sending them out over the air so that listeners can receive them in their homes. What is new about it? It uses different – very much shorter – wavelengths from those that have been used in broadcasting for so many years.

On most receivers there is a long-wave band, with the wavelengths marked on the dial in metres from about 1,000 to 2,000 metres. The BBC’s main Light Programme transmission is found on 1,500 metres. Then there is a medium-wave band, with dial markings from about 185 to 570 metres. This band is used by the stations transmitting the various Home Services, the Third Programme, and Network Three, as well as the auxiliary transmission of the Light Programme on 247 metres.

VHF receivers usually have a dial marked with numbers from about 87.5 to 100. These numbers are, in fact, frequencies – in megacycles-per-second, or Mc/s – but we can think of them simply as numbers on a dial.

The list of VHF stations in this supplement and the headings of the programme pages in Radio Times show at which number you can find the programme you want.

The new VHF service, apart from using a different waveband, also uses a new transmission technique known as frequency modulation, or FM. On some receivers the VHF band is indicated by the letters FM. It can be said that FM plays a most important part in providing VHF listeners with better reception.

The advantages

WHAT ARE THE ADVANTAGES OF VHF? There are three main ones, and they are important: (1) almost complete freedom from interference from foreign stations; (2) the reduction and in most cases complete elimination of interference from electrical appliances; and (3) greatly improved quality of reception which adds realism to all programmes and is a real boon when listening to music.

This new system involves the use of many new transmitting stations as well as a new kind of receiver. Why is all this complication necessary? Simply because the long-wave and medium-wave bands already mentioned are full up-over-full, in fact-with British and foreign stations crowded together and interfering with each other. Listeners in coastal and other outlying districts will know only too well how serious this interference is, and it is liable to grow worse. Many types of electrical appliance can also interfere with long-wave and medium-wave reception.

The only solution was to branch out into a completely new waveband – the VHF Band. The old system of broadcasting using the long-wave and medium-wave bands will continue so that listeners who bought their receivers before the introduction of VHF can continue to use them. But the new service provides the answers to most reception problems for those who use it.

BBC transmitters

THE BBC has so far built and brought into operation thirteen VHF transmitting stations (as well as two temporary ones) which has made the VHF service available to some 95 per cent. of the population of the United Kingdom. With the few exceptions, all these stations broadcast the Home Service appropriate to the Region in which they are situated as well as the Light Programme, the Third Programme, and Network Three. The VHF service also provides the opportunity for the transmission of items of local interest.

Completing the Coverage

AS well as the four stations being brought into operation this year, further stations are planned to increase the coverage of the VHF service to over 98 per cent. of the population. Two of these, in the Orkneys and in the Peterborough area, have already been authorised.

How to make the most of VHF

THE RECEIVER

BUY the best you can afford. The more expensive sets really do give something extra. There are receivers for VHF only, combined long-wave, medium-wave and VHF receivers, and television sets which include provision for listening to the VHF sound programmes.

THE AERIAL

THE full benefits of the VHF service cannot be obtained unless a suitable aerial is used. Many VHF receivers have an aerial fitted inside the cabinet, and this may be all that is needed in favourable reception conditions, particularly in areas fairly close to one of the new VHF transmitting stations. Further away, a simple indoor aerial either in the room or in the roof-space may be suitable, while towards the limit of the station’s coverage you will need an outdoor aerial above the roof.

Sometimes reception conditions are favourable even fairly close to the transmitting station, particularly in hilly districts. Hills or tall buildings between the listener’s home and the transmitting station can seriously weaken the signal, and if you live close to a main road you may get ignition interference from passing motor-vehicles (this usually sounds like a ticking noise from the loudspeaker, varying with the speed of the engine).

Other symptoms which can occur in difficult reception conditions and where an unsuitable aerial is used are that one or more of the programmes may sound distorted and that they may be received at widely different strengths, although the transmitting arrangements at each station are the same for all the programmes.

The VHF aerial is smaller than that used for television, and is fixed horizontally although the transmitting arrangements at each station are the same for all the programmes.

A VHF AERIAL is generally similar to a television aerial, but physically smaller and fixed horizontally. Such aerials have directional properties and should normally be turned so that the horizontal arms are at right-angles to the direction of the transmitting station. If the aerial is inside the receiver you may need to turn the whole, cabinet round to get the best results.

Where local reception conditions are poor, aerials with two or more arms are often used. The direction in which the aerial is turned
and its precise position may call for some experiment to arrive at the best result. Sometimes moving the aerial a few feet one way or the other can make all the difference.

A local radio dealer who has made a careful survey of reception in his district will know what problems are likely to be encountered and how to solve them.

TUNING THE RECEIVER

THE map and list of stations in this supplement, as well as the tuning-dial numbers in the programme-page headings of Radio Times, show which station covers your particular area. In many parts of the country it is possible with a sensitive receiver to tune in several of the VHF stations. But only the local one meant to serve your area is likely to give you first-class reception. When you have found the best tuning point for each programme note the dial reading for future reference.

Be sure to tune-in the programme exactly. Inaccurate tuning causes noisy reception and can ruin the programme quality. Use the dial number and the tuning indicator – if there is one – as a guide, but make a final slight tuning adjustment to get the best result. The dial should be set between the two points where the signal becomes noisy. This is not necessarily the point where reception is loudest.

The BBC is anxious that every listener should enjoy the VHF service at its best. In case of difficulty see your radio dealer, or write to the Engineering Information Department, BBC, London, W.1.