The UK 405-Line Television Network

n the United Kingdom there was never the proliferation of broadcasters that appeared in many other countries. The first was an organisation of radio receiver manufacturers who in 1922 persuaded the British government to award them a licence to broadcast material of an informative and entertaining nature rather than merely engineering tests, which was all they were allowed to transmit previously. They grandly called themselves The British Broadcasting Company (BBC) and five years later in 1927 they were incorporated by royal charter as the British Broadcasting Corporation, financed by receiver licence fees and, for a while, a tax on valves.

The first time this monopoly was broken was in 1955 when the Independent Television Authority (ITA) was formed to transmit commercial television programmes (the so-called Independent Television - ITV) in competition with the BBC. On 12 July 1972 its remit was expanded to encompass local radio stations and it became the Independent Broadcasting Authority (IBA). Since then, other authorities have come and gone, and broadcasters operate in the UK in a less regulated and more fluid environment, but the BBC remains as the only non-commercial public service broadcaster.

The BBC was distinctly cold about television at first. A lot of the development was done by companies such as EMI and Marconi, and of course the enterprising John Logie Baird who promoted his mechanical system at every opportunity and even managed to persuade a BBC engineer to transmit his signals after closedown on medium wave. In 1932 the BBC was persuaded to take over test transmissions on Baird's crude system, but it soon became apparent that the time had come for a proper high-definition public television service and in 1936 the government empowered the BBC to start tests using Baird's improved 240-line mechanical system alongside a new all-electronic system.

So the 405-line monochrome television began service on 2 November 1936 from a BBC transmitter at Alexandra Palace on channel B1 in vhf Band I (vision 45.00MHz, sound 41.50MHz). The system had been devised in 1934 by three members of the EMI research team meeting one Sunday morning at the home of Alan Dower Blumlein. Their intention had been to design a pulse divider to drive an all-electronic version of the Baird 240-line standard, but they realised it would be a simple matter to jump from 243-lines (3x3x3x3) to 405-lines (3x3x3x5) , and so the new system was born.

The transmissions were originally double sideband, and even when vestigial sideband transmissions were introduced, there was always a gap in the Band I plan where Ally Pally's upper sideband used to be. The service was shut down on 2 September 1939 for the duration of the war, and when transmissions recommenced in 1946 they were still on the old 405-line standard, rather than the 625-line one that was being proposed elsewhere in Europe. In 1955 the ITA opened the first commercial television station broadcasting to London. It used the same transmission standard, System A, as classified by the CCIR (Comité Consultatif International des Radio Communications - the International Radio Consultative Committee) around 1950, but a higher frequency band - Band III.

In the late 1950s and early after-closedown experimental colour transmissions were made from the BBC's London transmitter using a variant of the American NTSC (National Television Systems Committee) colour system adapted for 405-line/50 fields per second operation. The tests became quite comprehensive, featuring slides, films, live studio camerawork and even outside broadcasts. Receivers were installed in people's homes to assess the problems involved with reception, but of course demonstrations were also given at the studio to visiting parties. At first both the studio and transmitter were housed at Alexandra Palace, but in 1957 the Crystal Palace site was brought into use and from there uhf and 625-line NTSC colour test transmissions were eventially made. The ITA favoured the French SECAM (Système en Couleur à Mémoire) and made some test transmissions in the autumn of 1962 to assess monochrome recediver compatibility.

The ITV colour tests are less-well documented than the BBC ones, but Michael Cox, then working for ABC Television at Teddington, Middlesex, remembers that in 1963 attention switched to 625-line SECAM, PAL and NIR tests in anticipation of the opening of a second 625-line service along the lines of BBC2, the 625-line uhf sister service to BBC1. However, when no announcement was forthcoming from the new Labour government by 1965, ABC began demonstrating 405-line colour using the PAL system, in the hope of starting a colour service sooner rather than later. It was eventually announced that the only colour standard would be System I 625-lines PAL, to be introduced firstly on BBC2 from mid 1967, and that BBC1 and ITV would continue on 405-lines vhf in monochrome only until 1970 when they would be duplicated in 625-line PAL colour on uhf. (The duplicated services actually started in November 1969, making 405-line receivers redundant in some areas for the first time.)

However, the first departure from 405-lines had been made in April 1964 with the introduction of BBC2 in London on channel E33 in Band IV on 625-lines. It was proposed that four networks nationwide should be available on the uhf bands IV and V, and that as well as the existing BBC1 and ITV services being duplicated there in 625-line PAL colour, a new, fourth, channel would be added at a later date. Following the addition of colour to BBC2 in 1967 and to BBC1 and ITV in 1969, the uhf network expanded rapidly in the 1970s. Channel Four, a public service network financed originally by advertising revenue from the ITV companies, began in November 1982, on uhf 625-lines only.

As the 625-line uhf service progressed, it was decided to close down the 405-line service in a piecemeal manner between 1982 and 1986, starting with the smaller transmitters and ending with the main ones. However, by 1984 it was clear that not many viewers still watched 405-line sets and the close-down was accelerated. The last main transmitters were ceremonially shut down on 1 and 2 January 1985 in England and Scotland respectively. At the same time it was decided that Bands I and III should no longer be used for broadcasting in the UK, and so the spectrum was sold off to other services. Fifteen of the BBC sites and four of the ITA/IBA sites only ever radiated 405-line television transmissions and have not been re-used for broadcasting services since.

405-line television had also been used in the Irish Republic, bringing its 625-line-originated service to owners of 405-line-only receivers who had bought them to pick up the BBC and ITV signals from the UK, and an excellent account can be found on Richard Logue's irishtv webpages.

An alphabetical list of BBC and ITA/IBA 405-line transmitters including National Grid References is also available as a web page.

he characteristics of the 405-line transmission system are as follows: Field frequency: 50Hz; Line Frequency: 10 125Hz; Interlace: 2:1; Aspect ratio: 4:3 (5:4 until 3 April 1950); Channel width: 5MHz; Vision Bandwidth: 3MHz; Sound/Vision spacing: -3.5MHz; Width of Vestigial Sideband: 0.75MHz; Vision Modulation: Positive (Sync Pulse Tips = 0%, Black Level = 30%, Peak White = 100%, no Pedestal); Sound Modulation: AM; Field repetition period: 20ms; Active field period: 188.5 lines; Field blanking period: 14 lines (the original 1935 spec required 'at least ten lines'); Field sync/blanking format: Four lines each containing two 40µs pulses separated by 10µs followed by ten lines of blanking; Line period: 100µs; Active line period: 80µs; Line blanking period: 20µs, of which line sync pulse is 10µs.

Experimental colour transmissions were carried out by the BBC in the 1950s. Colour coding system: NTSC; Subcarrier Frequency: 2.6578125MHz. In the autumn of 1962 the ITA conducted transmission tests in 405-line colour in SECAM, and in 1965 ABC Television demonstrated 405-lines PAL. The SECAM fm subcarrier frequency was nominally 2.66MHz with a deviation of ±250kHz and the PAL subcarrier was 2.66034375MHz.

There are complete specifications of the System A 405-line standard along with pulse waveform diagrams in World TV Standards and Waveforms.

he following contour maps are taken from the ITA yearbook "ITV 1967" and represent the state of the ITV network at the end of the first phase of development, when the original companies were all on the air. New franchises were about to be awarded, and new companies would start in 1968.

The ITV 405-lines vhf network began with the Croydon transmitter at Beulah Hill in London, opened on 22 September 1955. The last transmitter to be opened was Newhaven, a dependant of Chillerton Down in the South of England, on 3 August 1970. They were closed down in reverse order, starting with Newhaven amongst others in 1982 and finishing with Croydon and the main regional transmitters on 1 and 2 January 1985.

Only three vhf transmitters (Newhaven, Ballycastle and Aviemore) were opened by the ITA after the official start of the uhf service in November 1969.

North-East Scotland A flurry of activity on 30 September 1961 brought the twelfth ITV service to life from the Durris and Mounteagle transmitters. Whilst Mounteagle was conventionally sited near to the existing BBC station at Rosemarkie, Durris was a departure from this and attempted to cover the 100 miles of coastline from Arbroath to Peterhead. It did so from a 1 000ft mast beaming power in two 400kW erp lobes to the north and to the south-west. Rumster Forest, opened on 25 June 1965, brought coverage to Orkney and Caithness by rebroadcasting the Mounteagle signal. On 15 October that year reception in Dundee was improved when Angus came on air, rebroadcasting programmes from Durris. Each was unmanned and remotely controlled from its parent station. Grampian Television seven days a week Grampian has survived all three contract renewals.

Central Scotland The first region outside England to get ITV, Central Scotland's service began on 31 August 1957 from Black Hill. The original 750ft mast at Black Hill incorporated a novel 16-stack directional aerial system that was mounted inside the lattice structure of the mast rather than outside or on top, as was the usual practice. The intention was to reduce wind loading and icing-up. Unfortunately, the anticipated polar response pattern and polarisation were not obtained, but it wasn't until 10 July 1961 that a 1 000ft mast with a more conventional array was brought into service. Scottish Television seven days a week Scottish continues to serve Central Scotland

A highly-trained ITA technician dons his standard-issue white lab coat in order to track down the radiated signal from the original Black Hill mast.

Borders The ITV service for the Borders, the eleventh region so start, began on 1 September 1961 from Caldbeck, closely followed by Selkirk on 1 December. Here, two principal transmitters were used to serve two separate populated areas, divided by the Cheviots. A radiation pattern of 70kW to the north-west, across the Solway Firth, and 100kW erp to the north-east and south-west from the 1 000ft mast at Caldbeck penetrated far enough to feed both Selkirk and Richmond Hill, which each rebroadcast the signal. Power was restricted to 20kW to the south-east in order to avoid interference to other services. Selkirk, serving Berwick-upon-Tweed with an erp of 25kW from its 750ft mast, was the first unmanned remotely-controlled station to be set up by the Authority. Richmond Hill on the Isle of Man used the original 200ft mast from Croydon, suitably strengthened in anticipation of its carrying uhf aerials in the future, and began transmitting on channel 8 on 26 March 1965. Border Television seven days a week Border Television is still with us, though thankfully it has ceased production of "Mr and Mrs" with Derek Batey.

Northern Ireland The eighth region was Northern Ireland, served by Black Mountain from 13 October 1959. 750ft was the highest mast that could be used at Black Mountain because of the nearby airport. 100kW was radiated to the north- and south-west, but only 20kW to the east in order to reduce interference in the Winter Hill service area. The Strabane station, opened on 18 February 1963 was similarly constrained with an erp of 90kW from its 1 000ft mast to the north and south and 10kW to the east and west to prevent signals straying into the Republic of Ireland. Ulster Television seven days a week Ulster is still going. Does no one else want these far-flung outposts?

North-East England Seventh in line, the North-East service opened on 15 January 1959 from the Burnhope transmitter. Situated a few miles away from the BBC's Pontop Pike station the directional aerial beamed 100kW erp to the north and south along extremely hilly terrain which required a 750ft mast to avoid 'shadowing'. It clearly managed this quite successfully, as it was still the sole 405-line transmitter in the region when the network was completed. The only other single-transmitter regions were Channel (Fremont Point), London (Croydon) and Lancashire (Winter Hill). Tyne Tees Television seven days a week Tyne-Tees has kept going, though in the seventies it combined with YTV in Trident Television, which was later split up. Now it has combined with Yorkshire again, and also Granada, and they're all in bed with Carlton.

	North of England The third region to have ITV, the North required two Band III transmitters to cover the same area as the BBC's Holme Moss. Winter Hill to the west of the Pennines started on 3 May 1956 and Emley Moor in Yorkshire followed six months later on 13 November. Sixteen possible locations for the Yorkshire station were studied theoretically, and balloon transmitter tests were made at a shortlist of four before Emley Moor was finally chosen and a 450ft tower built to launch the service. The contour maps shown are for the tubular steel construction masts brought into service in 1966, replacing the smaller lattice towers at both stations. The 1 265ft mast at Emley Moor iced up and collapsed in March 1969, six months before the start of the three-channel uhf colour service. A temporary mast was erected, followed by the present concrete structure, at the time the highest of its kind in Europe, as was the tubular mast before it along with its twin at Belmont. The tubular steel mast built at Winter Hill is 1 015ft high. When the ITV franchise was split in 1968 the BBC added a Band III transmitter to Winter HIll in order to transmit the Manchester version of Look North. A new version produced in Leeds was transmitted from the existing Holme Moss Band I transmitter. There were several BBC Band III filler stations around the country, including one at Belmont which carried the BBC1 Leeds service (whereas the ITV service was from Anglia TV in Norwich). Granada Television Monday to Friday Granada is still going strong, of course. In 1968 it won the seven-day franchise for the North West, when the Yorkshire region was advertised separately. ABC Television Saturday and Sunday ABC held the weekend contract in the North and Midlands regions, with studios in converted ABC cinemas in both Birmingham (which it shared with ATV) and Manchester. It lost its contract in 1968, when Granada, Yorkshire and ATV took over the North and Midlands seven days a week.	The present self-supporting concrete tower at Emley Moor completed in 1972. The height is 900ft with a base diameter of 80ft tapering to 20ft at the top. The 1 265ft tubular steel mast under construction at Emley. The 450ft lattice tower which it was to replace can be seen to the left.
From an ITA press release of 1965: I.T.A.-B.B.C. Aerial Masts.- The final stages in the contruction of a 1,265 ft cylindrical television mast at Emley Moor, near Huddersfield, Yorks has now been reached. This mast, which is the tallest structure in Europe, is one of three being built by B.I.C.C. and E.M.I. to a new design for the I.T.A. and will be shared with the B.B.C. The other masts are located at Winter Hill, Lancs. (1,015 ft) and Belmont, Lincs. (1,265 ft). The mast consists of a 9 ft diameter steel tube (with a lift inside to give access to the aerials) for the first 900 ft. At the top of this is a 365 ft lattice structure to carry the television aerials, which will be enshrouded by a fibreglass tube. Starting from the top, the aerial sighting is: 1 and 2. Two u.h.f. aerials each capable of carrying two services; 3. Band III aerial for the I.T.A. (to replace the aerial on the existing tower); 4. Band III aerial for future development; 5. Band II aerial capable of carrying three f.m. sound services; 6. Outside broadcast dishes for the B.B.C.; 7. Dishes for the G.P.O.; and 8. Outside broadcast dishes for the I.T.A. The present mast is in the background.

East of England East Anglia, the ninth ITV region region to open, was served by Mendlesham from 27 October 1959. A transmission site to the south-east of the required service area was chosen in order to reduce interference in the Chillerton Down service area and in France. To compensate, the erp beamed towards the intended service area to the north and west was 200kW from a 1 000ft mast. Like many ITA masts, this was the tallest to have been built in Europe at the time, and was the first of six 1 000ft masts to be used around the country. Two further stations opened in 1965. Sandy Heath (13 July) rebroadcast signals received directly from Mendlesham at an erp of 30kW to the north towards Bedfordshire from a 750ft mast. Belmont (20 December), designated a main station because it was to be shared with the BBC, was furnished with the first of the ITA's 1 265ft 'tallest in Europe' tubular steel masts. Radiating its 20kW erp signals throughout Lincolnshire it rebroadcast Anglia programmes received from Mendlesham at Massingham in Norfolk that were then microwaved to Winceby in Lincolshire and thence to Belmont near Louth. Anglia Television seven days a week Another survivor of every franchise renewal, though the Belmont area was lost to Yorkshire in the seventies. The Anglia Knight information is taken from a postcard sold by Anglia Television in the sixties.

The ITA were nothing if not patriotic as they demonstrate here by flying the union flag at the Belmont station.

South Wales and the West of England The St Hilary transmitter brought programmes to South Wales and the West on 14 January 1958 making it the fifth ITV region to open. Serving the area around the Severn Estuary and Bristol Channel St Hilary radiated 200kW erp omnidirectionally from a 750ft mast. The ITA would have preferred a 1 000ft tower, but the proximity to Rhoose Airport precluded this. The shorter wavelength Band III signals provided much poorer coverage than that enjoyed by the BBC's Band I service, and disappointed viewers had to install hefty directional receiving aerials and fringe-area receivers. TWW seven days a week in the English language TWW stands for Television Wales and West.

The 500ft tower built on a former tennis court at Croydon in 1962 London London was naturally the first region to have an ITV service when the Croydon transmitter went on the air on 22 September 1955. The BBC had begun television transmissions in 1936 from Alexandra Palace in north west London, but had recently moved to Crystal Palace, so the ITA chose a nearby site, Beulah Hill in Croydon, for their first station. The mast they used was a 200ft standard design, but the 10kW sender was the first-ever Band III transmitter to be constructed in the UK and was in fact the laboratory prototype. After a few months a production-line version of the transmitter was installed as a stand-by unit and the output of this was later combined with the original to double the operating power. For the next few years the ITA concentrated on building stations up and down the country at the expense of improving the London coverage, but in 1962 Croydon sported a new slim 500ft tower and a maximum erp of 400kW. Rediffusion Television Monday to Friday Associated Rediffusion dropped the "Associated" part of its name after a franchise re-jig, though it seems to have reacquired it now (though not its franchise). Rediffusion had a pop show at 7pm on Fridays called "Ready, Steady, Go! The Weekend Starts Here". How prophetic they were, since when they lost the weekday contract to Thames in 1968 the changeover time was brought forward to 7pm on Fridays, when London Weekend Television took over until midnight on Sundays. Thames themselves lost the weekday contract to Carlton in 1993, but LWT continues at weekends. ATV Network Saturday and Sunday Associated Television comprised many important theatrical figures, and so many acts that had remained unavailable to BBC televison suddenly started appearing on the commercial channels. In the sixties ATV were in the forefront of selling to America, and had their own colour tv studio based on the US NTSC system.

South-West England The two transmitters at Stockland Hill and Caradon Hill brought the number of ITV regions into double figures on 29 April 1961. Two stations were required in order to provide similar coverage to that of the BBC's North Hessary Tor transmitter which was situated centrally within the region on Dartmoor, and 750ft masts were needed because of the hilly terrain. Caradon Hill radiated a tight figure-of-eight pattern with an erp of 200kW in order to reach Land's End, but to avoid interfering with Dublin. Similarly Stockland Hill had a boomerang-shaped pattern with lobes to the north- and south-west. The erp in those directions was 100kW, but only 10kW was radiated to the east towards Croydon which used the same channel, 9. Some energy had to be directed towards Alderney to feed the Channel Islands transmitters, but that was restricted to 20kW - just sufficient in practice to provide a high enough signal-to-noise ratio for rebroadcast. Westward Television seven days a week The franchise situation south of the Wash has always been volatile, and Westward went west in 1982 to be replaced by TSW, which lost its franchise in 1993 to West Country Television.

South and South-East England The opening of the Chillerton Down station on 30 August 1958 made this the sixth region to receive ITV. Covering central southern England, Chillerton Down was built near to the BBC's Rowridge station on the Isle of Wight. Opposition to the second mast was only marginally less strong than that to the alternative of an enlarged shared station at Rowridge itself, but a slim 750ft mast was eventually accepted. The site chosen to serve the east of the area, at Dover, provided the required coverage with no problem, but reducing the power radiated backwards across the Channel towards France proved a headache for ITA engineers. After a protracted series of test transmissions during which receiving equipment mounted aboard a helicopter was used to ascertain the true radiation pattern the station went on full power from its 750ft mast on 31 January 1960. Southern Independent Television seven days a week How! Southern lost to TVS in 1984, who themselves were replaced by Meridian in 1993. The franchise boundaries along the south coast have also changed since 1967.

	Channel Islands Lucky Channel Islanders joined the ITV network as the thirteenth region on 1 September 1962 when the Fremont Point transmitter was brought into service. Because of the remoteness of the Channel Islands it was not possible to use a microwave link to send programmes to the transmitter at Fremont Point. Instead, a normal ITV transmission had to be received off-air from a south-coast station and rebroadcast. Unfortunately, the only channel available for use on the Islands that would not suffer from, or cause, interference was channel 9, which was the same one used by the nearest mainland station at Stockland Hill, which was the intended source for rebroadcasting. For that reason a receiving station using a 30ft parabolic dish aerial was built at Braye Bay on Alderney which sent on the signals by microwave to Fremont Point. Alderney viewers had to make do with direct reception of Chillerton Down on channel 11, and that was also used as a back-up signal when interference was too bad to use the Stockland Hill signal. A further alternative was to rebroadcast the Caradon Hill channel 12 signals received on Jersey at Fremont Point itself.	625 Lines and Digital for the Channel Islands 625-line uhf colour transmissions did not start from Fremont Point until July 1976 because of the problems of receiving the much shorter wavelength transmissions from Stockland Hill. A revolutionary type of aerial called SABRE (Steerable Adaptive Broadcast Reception Equipment) was developed which uses circuitry to tweak the response of the array in order to obtain the best signal from Stockland Hill whilst nulling out interference from the handful of transmitters around Europe that use the same channel as their signal levels rise and fall with the ever-changing propagation conditions. All analogue television transmissions have now ceased in the Channel Islands. The regional BBC1 and ITV1 services, amongst hundreds more, are available on DVB-S satellite and the three DVB-T public service multiplexes (BBC, commercial and High Definition) are now available from all eight uhf terrestrial stations on the islands.
	Channel Television seven days a week Channel chugs along still, though its output is, as in the past, largely based on programmes from the south west region of the network.

or a glimpse at test cards and captions from the 405-line era and beyond, please see the Test Cards, Tuning Signals, Clocks and Idents section of this web site.

Test Card F of course is the very icon of colour television with its innovative use of a picture in the centre circle. It first appeared on BBC2 in July 1967 but when the BBC1 and ITV networks were duplicated on 625-lines uhf from 1969 Test Card F was simultaneously radiated in black and white on 405-lines vhf. The frequency gratings which are multiples of 0.5MHz on 625 lines work out at some very strange values on 405 lines - 0.98, 1.63, 2.28, 2.60, 2.93 and 3.41MHz. Since the highest vision frequency transmitted in System A is 3.0MHz, the finest gratings appear as a uniform grey block.

If anyone hasn't heard, the model is the then nine-year-old Carole, daughter of the late George Hersee who died in 2001 and who designed the test card in 1967.

I have taken the opportunity of presenting Test Card F here at its 405-line resolution of 377 active lines and 3MHz bandwidth. Not bad for an old system, is it? For the best effect, zoom the picture to about ten inches across and hold a large oil-filled plastic lens in front of your monitor. Want to see it in colour? Attach a sheet of plastic film stained blue at the top, green at the bottom and a peachy colour in between.

Ah, those were the days...

Television Website Bookmarks   Mike Brown/MB21/Ether.net Andrew Emmerson/Paul Stenning/405 Alive/British Vintage Wireless Society Keith Hamer David Laine/Vintage Broadcasting Richard Logue/irishtv Darren Meldrum PARAS - independent advice about the digital switchover in the UK Richard Russell Justin Smith/Aerials and TV Andrew Wiseman/625 Room Bill Wright

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Pembers' Ponderings

Compiled by Alan Pemberton
Sheffield, South Yorkshire, England
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