How to receive BBC-2 

22 May 2017 tbs.pm/12014

Originally published by the BBC Engineering Information Department in July 1965

FOREWORD

The BBC’s second television programme, BBC-2, is now in full swing and is being rapidly extended over the country. The purpose of this booklet is to tell you about plans for this expansion and to give some advice on how to receive it.

BBC-2 is transmitted on the 625-line standard. This has important advantages over the 405-line standard, which for the time being will continue to be used for BBC-1. The 625-line standard gives a picture of higher definition and has the added advantage that the line structure is less visible, which is particularly important with the larger screens now being widely used. The use of frequency modulation (FM) for the sound channel gives a sound signal less subject to interference. The 625-line standard is also used in most countries on the Continent of Europe, so that the international exchange of programmes becomes easier.

The BBC-2 transmissions are in the UHF (ultra high frequency) bands. These higher frequencies, as explained in this booklet, have characteristics which have a more marked effect on reception than have the lower frequencies of Bands I and III; the information about receiving aerials is particularly important in this respect. Where reception problems do arise viewers should consult their television supplier who will be able to give advice about receivers and aerials to suit local conditions. The BBC Engineering Information Department will also be pleased to help and advise on general matters concerning UHF television reception.

BBC-2 — Plans for the extension of the new service

The BBC-2 service began on 21 April 1964, using a single transmitting station at Crystal Palace, serving the Greater London area and part of south-east England. The network of transmitters radiating BBC-2 programmes will be extended to the rest of the country as quickly as possible by the opening of new stations, many of them on the same sites as existing BBC and ITA stations. About two-thirds of the population of the United Kingdom will be within range of the new service by the end of 1966 or soon afterwards when the first group of high-power stations are expected to be in operation (see list below). Some sixty high-power stations supplemented by a large number of medium- and low-power stations will be needed to serve the whole country.

Viewers in the Birmingham area were able to receive BBC-2 from 6 December 1964. Temporary equipment was installed by the BBC at its Sutton Coldfield station for this purpose and although the radiated power and range of the temporary installation was less than that of the permanent station, which is due to be completed in the autumn of 1965, a service was provided for some two million people in the City of Birmingham and its environs.

During the autumn of 1965 further high-power stations will be opened at Winter Hill, Lancashire, and Emley Moor, Yorkshire, at Wenvoe in South Wales, at Rowridge in the Isle of Wight, and at Black Hill in Central Scotland. The scheduled opening dates of these stations are shown in the list below.

UHF transmissions tend to behave rather like rays of light so that hills and other obstacles cast shadows in which the signal strength may be weak. The BBC proposes to build ‘fill-in’ stations to serve most of these areas.

A survey of the service area of the Crystal Palace station has shown that fairly extensive shadows of this kind exist in the Reigate, Tunbridge Wells, Guildford, and Hertford areas. Some viewers in these areas find it difficult to receive good pictures from the Crystal Palace station direct and the BBC is building the first four ‘fill-in’ stations in these areas. The Hertford, Tunbridge Wells, and Reigate stations will be completed and in operation by about the autumn of 1965; the Guildford station has been delayed by difficulties over its site but it will be brought into service as soon as possible. ‘Fill-in’ stations will be built as necessary to serve similar shadow areas around the main stations in other parts of the country.

The frequency channels to be used

The new BBC programme is transmitted on UHF (ultra high frequency), which had not been used for television in the United Kingdom, except for test transmissions, until the start of BBC-2. In the past, the television services in this country have used frequencies in the VHF (very high frequency) range, with BBC television in Band I (41 to 68 Mc/s), and both BBC and ITA in Band III (174 to 216 Mc/s).

The ultra high frequency range used for television extends from 470 to 854 Mc/s and is divided into two bands, Band IV (470 to 582 Mc/s) and Band V (614 to 854 Mc/s). Band IV contains 14 channels, numbered 21 to 34, and Band V contains 30 channels, numbered 39 to 68. (Channels 35 to 38 are being reserved for purposes other than television.) Each transmitting station can be assigned up to four channels. One of these will be used for the new programme BBC-2, while the other three will be reserved for any other new programmes to be introduced in the future, and possibly for the duplication of the existing BBC and ITA programmes on 625 lines (see table on page 11).

Receivers

Dual-standard television receivers designed to receive BBC-2 as well as the existing programmes have now been on sale for some years. It will in some cases be possible to convert older receivers to receive BBC-2, in particular those manufactured since about the end of 1961, but the older the receiver the less worth while the conversion becomes.

Receivers made before 1961, many of which were still being sold in 1962, cannot usually be converted and viewers with such receivers will need new ones to receive BBC-2. Such viewers can, of course, continue to use their old receivers for BBC-1, if they wish, because the proposed change in the line standard of BBC-1 will not take place for some years.

A UHF receiving aerial will be needed in all cases for receiving BBC-2 (see below).

Colour television

Colour television will later be introduced as a part of the BBC-2 programme, possibly in 1967. It will then be available in all areas where BBC-2 stations are in operation.

The colour television system to be used has yet to be decided but it will in any case be ‘compatible’. This means that black-and-white receivers will be able to receive the colour programmes as black-and-white pictures. Viewers can, therefore, equip themselves now with UHF 625-line black-and-white receivers and aerials with the knowledge that they will be able to receive all the programmes transmitted in this band. Colour receivers are likely to be expensive; you can expect to pay about three times as much as you would for a black-and-white receiver.

Television reception on UHF

A television receiver has to depend upon its aerial to pick up the programme which it is required to receive, and an efficient aerial is indispensable for good reception. This is particularly the case for reception in the UHF bands, and viewers are unlikely to obtain the full benefit from the 625-line transmissions in these bands unless a suitable and properly designed receiving aerial is used. In the majority of cases the aerial will need to be of the multi-element type, and only in a few exceptionally favourable locations is it likely that a very simple outdoor or indoor aerial will be found to be fully satisfactory.

A UHF aerial rod (i.e. a half-wave dipole) is only about one-tenth of the length required for Band I reception. For this reason, it ‘picks up’ less of the signal and delivers a much smaller voltage to the receiver. However, the smaller size makes it possible to construct compact and robust aerials with many more rods than are used in Band I. The greater number of rods results in a higher gain which compensates partly for the low ‘pick-up’ of the individual rods. In addition, the directivity (i.e. the ability to reject signals outside a narrow range of angles) is improved and this enables distortion, or ghost images, caused by reflections to be suppressed to a large extent.

On UHF, signals may be reflected by hills and tall buildings and their screening effect may cause sharp variations in signal strength; these effects are much more noticeable than they are in Bands I and III.

Because of this the proper installation of the UHF receiving aerial is of great importance and requires considerable care, particularly in difficult locations, in order to reduce multiple images (ghosting) caused by reflections, while still maintaining adequate signal strength.

UHF receiving aerials

The following notes give some guidance on the type of aerial required and on its mounting and adjustment.

  1. In unobstructed positions near to the transmitter simple aerials with 4 or 5 elements may be satisfactory. Most viewers in reasonably favourable locations within 20 or 30 miles of a high-power station will find an aerial of 8 to 10 elements suitable. A highly directional aerial, possibly in the form of a double or multiple unit, with 20 or more elements altogether, may be necessary in order to obtain satisfactory reception in an area where the direct transmission path is obstructed by a hill or tall building, and considerable care may be needed to find the best position.
  2. Indoor aerials and set-top aerials are likely to give poor and variable results, and are not in general suitable for UHF reception. Results with this type of aerial may be satisfactory in very favourable locations near to a transmitting station, such as in a flat or room on the side of a tall building nearest to the transmitter and with an unobstructed line-of-sight to it; but even in such locations the quality of the picture, although perhaps satisfactory, may be still further improved by the use of a relatively simple outside aerial fixed to a window-frame. When a set-top aerial is used, reception is liable to vary as people walk across the room.
  3. In locations directly in the shadow area of a large steel-framed building or immediately screened by a steep hill, really good reception may be impossible. Many such areas of poor reception will eventually be served by low-power local relay stations.
  4. If possible, mount the receiving aerial in a position from which there is an unobstructed line-of-sight to the transmitting aerial. If this is not practicable, place it in a high, open position with as few obstructions as possible in the direction of the transmitter, particularly avoiding obstructions close to the receiving point.
  5. All UHF receiving aerials are directional, the degree being dependent upon the number of elements used. For maximum signal level they must, therefore, be pointed accurately at the transmitting aerial, although it may be better at times to orientate the aerial slightly off the theoretically correct direction in order to reject or reduce undesired reflected signals. When installing the aerial, point it in the direction of the transmitting station and adjust the direction to give the maximum signal strength. Then move it over a distance of two or three feet, upwards and downwards and also sideways, on its mount before clamping it, so as to find the position that gives the best reception. Finally check the direction again. This operation requires two people, one to move the aerial, the other to watch the television screen and indicate when the best reception is obtained, i.e. the clearest picture, free from multiple images (ghosts) and ‘grain’. If the picture is faint and covered with ‘grain’ or ‘snow’ but is satisfactory in other respects, a marked improvement can usually be made by using an aerial amplifier. These are designed either to be fitted to the aerial itself or to plug in at the back of the television receiver. It is a simple matter for your television supplier to try an amplifier so that you can observe its effect.
  6. It may be possible to receive a satisfactory picture in a shadow area by pointing the aerial at a large building outside the shadow area which acts as a reflecting surface. Pictures received in this way do, however, tend to be less sharp than signals received direct, and to vary according to weather conditions.

Aerial (a) is installed in an average signal area and would be suitable in the great majority of cases.

Aerial (b) is in an area where the signal is weaker. Two aerials are therefore mounted side by side to ‘pick-up’ more signal; this arrangement also makes the aerial more directional and helps to get rid of ‘ghosting’ or distortion of the picture.

Aerial (c) is obviously in an area where the UHF signal is weak. Two aerials are mounted one above the other and an aerial amplifier is also used.

UHF aerials are smaller and lighter than those used for reception in Bands I and III and the wind resistance is very much less, so that a UHF aerial puts little strain on a chimney or other support.

N.B. Make sure that your aerial (and amplifier, if used) is designed to receive all the four channels shown in the table on page 11 for any one site.

  1. When a new aerial system is being installed which includes aerials for Bands I and III as well as for UHF, it is usually best to put the UHF aerial at the top of the mounting and spaced from the other aerials beneath it. If the UHF aerial is on a separate mounting, it should be well clear—at least two feet and preferably not less than about four feet—from other aerials, gutters, and roof surfaces.
  2. The aerial should be connected to the television receiver by low-loss coaxial cable. Flat ribbon feeder is quite unsuitable for UHF. It will sometimes be possible to use the same coaxial down-lead for Band I, Band III, and UHF aerials, in which case a special junction unit (diplexer) should be used at each end of the cable, at the top end to accept the feeders from Bands I and III and UHF aerials, and at the bottom end to provide two leads for the two input sockets to the receiver.
  3. Manufacturers have designed UHF aerials to work satisfactorily over a considerable band of frequencies. An aerial installed now for BBC-2 will therefore be suitable for receiving other programmes transmitted in the future on UHF from the same site. Provision has been made in future planning for up to four programmes to be transmitted from each site. A list of the first group of UHF stations and the probable channels to be used for them is given on page 11. Typical UHF receiving aerials are shown on pages 6 and 7.
  4. The use of a good UHF receiving aerial will become still more important as the network of UHF stations spreads throughout the country with some necessarily sharing the same channel. Such stations will be widely separated geographically but there will be the possibility at times, particularly in the outer parts of their service areas, of two or more stations being received simultaneously, thus causing interference and picture degradation. The use of vertical aerials at some stations and horizontal aerials at others will help to overcome this trouble; viewers can achieve considerable protection against interference from distant stations sharing the same channel by using a receiving aerial appropriate to the station serving their area, vertical or horizontal as the case may be, and having good directivity. It should be noted that the first group of main stations shown on page 11 will use horizontal aerials while the ‘fill-in’ stations will have vertical aerials. Note also that a relay station will use a group of channels different from the one used by its parent station and that the same aerial will not do.

Tuning a UHF television receiver

When a dual-standard or converted receiver is installed by a television dealer he ought to have left the various basic controls correctly adjusted and to have explained how to change from one programme to another. He will also have provided a copy of the manufacturer’s instruction booklet for the particular model of receiver and you are urged to study this carefully.

It is only necessary therefore here to give some very general guidance on tuning, indeed this is all that can be done because the arrangement and operation of the various control knobs vary considerably from one make of receiver to another.

On most receivers, it is necessary in order to receive BBC-2 to set a control knob marked ‘UHF’ or perhaps ‘625’. Where push-button tuning is provided, the tuning should have been correctly pre-set and the following remarks therefore apply only to receivers which have manual tuning. In this type of receiver, a horizontal or vertical scale is usually provided and marked with Channel numbers. You should tune to the channel for your area as shown on below.

The markings on the tuning scale must be regarded as approximate only and subsequent fine tuning will almost certainly be necessary.

Receivers vary somewhat in their behaviour when mis-tuned, but typical symptoms of mis-tuning are these:

  • Loss of sharpness. Fine details become blurred.
  • Sometimes ‘streaks’ appear to the right-hand side of light areas on a dark background or dark areas on a light background.
  • Buzz. The sound becomes confused by the addition of a buzzing noise.
  • Picture break-up. The picture wavers or wriggles from side to side in sympathy with the loudness of the sound.

Severe mis-tuning can result in complete break-up of the picture, picture roll (movement of the whole picture up or down the screen), or a loud buzzing noise in the loudspeaker.

As a general guide, the tuning should be carefully adjusted until the sound just causes the picture to break up. The tuning knob should then be turned in the opposite direction until this interference just ceases. The definition of the picture should then be at its best and the sound clear and free from any buzz.

The same procedure should be adopted if the pre-set tuning of receivers fitted with push-buttons needs adjusting. Reference should be made to the manufacturer’s instruction booklet for the method of adjustment, which may vary with different models.

BBC-2. First group of high-power stations planned.

High-power UHF 625-line Television Stations So Far Planned

 

Station      Channels      Expected Service Date
Crystal Palace, London 23, 26, 30, 33 In service
Sutton Coldfield, Warwickshire 40, 43, 46, 50 4 October 1965
(temporary station) In service
Wenvoe, South Wales 41, 44, 47, 51 12 September 1965
Winter Hill, Lancashire 55, 59, 62, 65 17 October 1965
Rowridge, Isle of Wight 21, 24, 27, 31 Before the end of 1965
Emley Moor, Yorkshire 41, 44, 47, 51 Before the end of 1965
Black Hill, Lanarkshire 40, 43, 46, 50 Before the end of 1965
Divis, Northern Ireland 21, 24, 27, 31 Summer 1966
Pontop Pike, Durham 54, 58, 61, 64 Spring 1966
Tacolneston, Norfolk 55, 59, 62, 65 Autumn 1966
Llanddona, Anglesey 53, 57, 60, 63 Autumn 1966
Belmont (E. Lincolnshire) 22, 25, 28, 32 Autumn 1966
Waltham-on-the-Wolds (Notts.) 54, 58, 61, 64 Winter 1966/1967
Mendip Forest 54, 58, 61, 64
Dover 50, 53, 56, 66 Late 1966
Durris, Kincardineshire 22, 25, 28, 32 Late 1966
Oxford 53, 57, 60, 63 Autumn 1967
North Yorkshire 23, 26, 29, 33 Autumn 1967
Sudbury (Suffolk) 41, 44, 47, 51 Summer 1967
Huntingdonshire 21, 24, 27, 31 Autumn 1967
Fill-in Stations—London Area
Reigate 53, 57, 60, 63 Autumn 1965
Tunbridge Wells 41, 44, 47, 51 Autumn 1965
Guildford 40, 43, 46, 50
Hertford 54, 58, 61, 64 Autumn 1965

 

Only one channel in each group will be used initially; this will be for BBC-2 and is shown in bold type, where known. The other three channels are for possible future services. Except for the stations due to be completed in 1965, the channel assignments are provisional and will be confirmed later.

The above dates must be regarded as target dates only. There may be delays due to difficulties in obtaining sites and to bad weather during mast erection and aerial installation periods.

 

 

BBC-2. Approximate service area of the UHF station at Winter Hill (above) and at Emley Moor (below). Reception will be easiest where the dots are most dense, but it must be realized that in hilly districts there will be pockets of poor reception which cannot be shown on this map. A number of low-power relay stations will be built to ‘fill in’ the main shadow areas.

 

 

A Transdiffusion Presentation

Report an error

Author

BBC Engineering Information Department Contact More by me

Tags

# # # # # #

You Say

2 responses to this article

Mike 23 May 2017 at 10:19 am

Interesting that what was eventually Sandy Heath is “Huntingdonshire” and Bilsdale is “North Yorkshire”. I guess that at press time the final sites hadn’t been selected, although the channel allocations were in place.

Paul Mason 27 May 2017 at 5:35 pm

In an age of multi channel TV those of us around in the late 1960,s forget the ,”snob value” of being able to receive BBC2, and later colour TV.
We were deprived of the experience for the first seven years after the channel came north but as you see above there was a lot of palaver involved in its reception. Those who read my posts know the story by now!

Your comment

Enter it below