Jeff: You may know that the medium wave channel of 648 kHz in the UK was allocated in 2017 by OFCOM, the British equivalent of the FCC, to the former offshore broadcaster Radio Caroline. Alan Beech, chief engineer for Radio Caroline, researched the fascinating and often contradictory history of the frequency, and wrote an article about it for the BBC engineering journal ‘Signal’. Ray Robinson, a friend of Alan’s, is now going to read the first part of that history.
Ray: Thanks, Jeff.
Before 648
During the 1930’s, the BBC established two separate broadcast networks, or programme streams, for the majority of listeners in the UK. The ‘National’ programme was just that, a single programme originated in London, but broadcast from a network of high-powered sites around the country. It provided a single national service. The accompanying ‘Regional’ programme was mostly broadcast from the same high-powered sites, but carried programmes reflecting and appealing to the various regions of the country, such as Midlands, North, London, West, Scottish and Welsh. Programmes for the regional service were produced in many of the country’s large provincial cities, though some were shared between regions. Thus, many of the historic broadcasting facilities, such as Brookmans Park, Moorside Edge, Lisnagarvey and Droitwich which continue to this day, came into existence. Here’s Alvar Liddell on the Regional Programme, reporting on the German 16 Point Plan on August 31, 1939.
Wartime broadcasting
Much changed during the war, first to supplement the high-powered stations with the addition of over 60 low-power ‘city’ transmitters. These were co-ordinated on a single frequency, 1474 kHz, 203.5 metres, to prevent ‘direction finding’ attempts by enemy bomber aircraft. This also meant that a city station could broadcast local programmes from a local studio in the event of local issues or loss of programme feed from London. Secondly, the regional and national programmes were replaced by the ‘Home’ and ‘Forces’ programmes, whilst some geographically advantageous transmitter sites were re-allocated to provide overseas transmission facilities into occupied Europe. Here’s a clip of the Home programme on D-Day, June 6th, 1944.
Whereas the Home programme was to carry serious content to reflect the gravity of the situation, the Forces programme was intended to provide light entertainment, comedy, dance band music and generally morale-boosting programmes to take the mind of servicemen off the grim tasks with which they were faced. Needless to say, the Forces Programme was also popular amongst the general public.
Black, Grey and White transmissions
During the war years, the UK Government’s Political Warfare Executive had undertaken various projects to broadcast into Europe and over the Atlantic using first their own low-power facilities from Gawcott and Potsgrove, and then their newly-established high-power transmission facility at King’s Standing near Crowborough in Sussex. This facility was built in 1942 and housed what was then the World’s largest broadcast transmitter, codenamed ‘Aspidistra’ and labelled onsite as Aspi 1 or ‘A1’.
The Home, Light and Third
At the end of hostilities, the Home service remained very much as it had been during the war, but with more regional content on a variety of frequencies around the country, while the Forces Programme was renamed the Light Programme and continued with light entertainment on a national basis. In 1946, the BBC wished to establish an outlet for serious (classical) music, drama and ‘intellectual’ cultured programming, and so the imaginatively-named Third Programme was created. After initial broadcasts started in 1946 from Droitwich on 583 kHz (514 m) at 150 kW, the Third Programme moved to Daventry from March 1950 on a newly-allocated frequency of 647 kHz (464 m) and using two new Marconi BD206 150 kW transmitters with a 725-foot high, centre-fed and top-loaded 5/8ths wavelength antenna mast that was designed to provide maximum groundwave and anti-fading propagation.
This excellent, central site covered the majority of England so just a small number of low-powered relay sites on 1546 kHz were required for the more distant parts of the UK.
Thus, as far as the BBC was concerned, these three separate services could cater fully for the needs of the nation – the Light Programme, mainly on longwave from Droitwich, but with some mediumwave ‘in-fill’ sites on 247 m (1215 kHz), the regional Home service on various mediumwave frequencies, and the Third Programme.
After the war, Aspi 1 continued to broadcast at 500 kW, though the programmes were generally of the BBC European service rather than the various shades of black, grey and white propaganda for which it had originally been built.
Although the Government and BBC were quite happy for the Crowborough facility to broadcast into Europe, they were less than enthusiastic that one of the many ‘cross-border’ pre-war stations, namely Radio Luxembourg, decided to recommence transmissions targeted at UK audiences. The Government tried just about every means within their jurisdiction to prevent it and discourage people from listening. However, with just three radio services available, all of which were run by various BBC committees, it is no wonder that Luxembourg rose to such prominence during the 1950’s with its popular commercial programming.
Offshore (1)
Roll on now to 1967. The Marine etc. Broadcasting Offences Act attempted to outlaw the offshore broadcasting stations and the need for an all-day popular music channel was finally recognised at Government level. At the end of September the Light Programme was split into two – the longwave service continued as before but was renamed Radio 2 and the mediumwave in-fills launched the new pop music service Radio 1. Powerful additional transmitters at Droitwich and Washford had to be commissioned to provide Radio 1 in the areas where there was only longwave coverage of the Light Programme and, conversely, new mediumwave transmitters in Scotland provided Radio 2 in areas where 247 m (1215 kHz) was now carrying Radio 1. The Third Programme became Radio 3, still on 647 kHz (464 m) from Daventry, and the regional Home service became Radio 4 – principally a national service, but with regional opt-outs on various regional frequencies. This is the way BBC Home Service closed down for the last time on Friday, September 29, 1967:
The coverage of Radio 1 and Radio 2 was somewhat lacking, with parts of the country unable to receive satisfactorily one or other of the programmes, so further changes became necessary… but it took a jaw-dropping 11 years to effect.
The MF/LF re-organisation
November 23rd 1978 saw a major re-organisation of radio channels across all of Europe, including the alignment of all stations to 9 kHz channel spacing. The BBC took advantage of this alignment to implement major changes to their mediumwave and longwave stations.
The growing roll-out of Local Radio during the 1970’s meant that the need for regional content on Radio 4 was redundant, so Radio 4 became a national service and moved onto the 1500 m longwave channel, freeing up four high-powered mediumwave channels which were then re-allocated around the country and split into two groups: 330 and 433 m (the former London and Northern Home transmissions) and 275 and 285 m (the former Midlands and West Home transmissions). Additional transmitters were introduced on each of these four wavelengths, but alternately staggered around the country, such that any overlap or mush zone between adjacent sites was minimised. 330 and 433 m (or 909 and 693 kHz on the newly-aligned 9 kHz channels) were assigned for Radio 2, whilst 275 and 285 m (1089 and 1053 kHz) were allocated to Radio 1. Radio 3, in turn, got the old hand-me-down poor coverage of Radio 1’s old 247 m (1215 kHz) – though it had national full-time coverage on VHF/FM, which by 1978, its listeners were more likely to use. Accordingly, the old Radio 3 frequency, which became 648 kHz, was no longer in service for domestic programmes. As this was the lowest mediumwave channel allocated to the BBC, it could offer the best daytime (groundwave) coverage and, combined with the fact that the channel was mostly in the clear across Europe, it was an ideal frequency for the European programmes of the World Service. Consequently, it was put into use at 500 kW from the Crowborough site in Sussex.
Some may consider it rather strange that the BBC’s best mediumwave channel served only an overseas audience whilst Radio 3 listeners got the worst coverage of the mediumwave national networks. But of course, all this took place at the height of the Cold War.
With the Aspi 1 500 kW transmitter equipment at Crowborough approaching 40 years old, it was coming to the end of its useful life and a replacement was required. Although coverage into Europe from Crowborough was good, the site was still some way inland (having been sited to hide it from enemy warships and aircraft) resulting in much signal being ‘wasted’ before it reached the English Channel.
Next week, we’ll continue the story, to see where the BBC moved the 648 kHz channel to next, and how it came to be allocated to Radio Caroline.
Wavescan is an international DX program, researched and written in Indianapolis by Dr. Adrian Peterson and in Los Angeles by Ray Robinson. Wavescan is produced in the studios of WMRI Shortwave in Okeechobee, Florida, by Jeff White.
The program frequently covers radio stations aboard ships. These reports are documented here.
