Thread by @ChrisGreenwayUK

99 years ago today, the Postmaster General issued a licence to the BBC to start experimental transmissions on longwave. As end of the longwave era approaches, I’ve written a lengthy🧵on the history of BBC longwave broadcasting.
The first instalment looks at the 1920s & 30s. #OTD

The BBC made the changes for two reasons:
- To tackle the problems outlined in posts 130-138 above
- To implement a new international agreement on the use of longwave and mediumwave – the Geneva Frequency Plan of 1975. 141/
en.wikipedia.org/wiki/Geneva_Fr…

At the time, the UK press criticised the Geneva Plan and the BBC, complaining that:
- Listeners would have to learn to find their favourite stations on new wavelengths
- One of the UK's mediumwave allocations (1215 kHz) would suffer major interference after dark from Albania
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In the end, the new plan and the BBC reorganisation provided a substantial improvement for most listeners.
The key to the changes was Radio 4 giving up all six of its high-power mediumwave networks. This gave several benefits....
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- Releasing three of the frequencies meant that Radio Wales, Radio Scotland and Radio Ulster each got the exclusive use of a high-power mediumwave channel, rather than having to be an opt-out from Radio 4.
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- The other three high-power Radio 4 MW channels were, along with a frequency released by the BBC European Service, used to make two good UK-wide mediumwave networks for Radio 1 (1053 & 1089) and Radio 2 (693 & 909).
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- This gave Radio 1 very much better coverage than its previous single-frequency network (1214 kHz), which had many "mush" areas where the signals from two or more Radio 1 transmitters on the same frequency interfered with each other.
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- In return for giving up all its high-power MW transmitters, Radio 4 took over Radio 2's longwave allocation, which meant it could finally become a truly single UK-wide service.
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To emphasise Radio 4's new capability to cover the whole of the country throughout the day, from 1978 it started identifying itself as "Radio 4 UK", though this ID was dropped in 1984.
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The new name was accompanied by a new piece of music, the Radio 4 UK Theme, composed by Fritz Spiegl. It was played at the start of each day's broadcasts from 1978. The dropping of the theme in 2006 provoked complaints. 149/ en.wikipedia.org/wiki/Radio_4_U…

The 1975 Geneva Frequency Plan had a bonus for the BBC. Along with renewing its longwave allocation of 200 kHz (1500 metres) - used since 1934, see post #24 – it gave the BBC an additional LW allocation of 227 kHz (1321 metres).
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The BBC's initial plan was to use both 200 and 227 kHz to give UK-wide coverage for Radio 4. Alongside the existing 200 kHz service from Droitwich, a transmitter on the same frequency would be installed at Burghead (on the coast east of Inverness) to cover northern Scotland. 151/

The two transmitters on 200 kHz would have a "mush area" in central Scotland where signals from both Droitwich (400 kW) and Burghead (50 kW) would be received at roughly equal strength, potentially interfering with each other.
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To cover the "mush area" area, the 227 allocation would be used by a third LW transmitter at Westerglen covering central Scotland. Many listeners in Scotland, Northern Ireland and the far north of England would be able to choose between 200 and 227 for best reception.
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But this initial plan was abandoned when it was realised that Poland’s 2,000 kW (2 megawatt) transmitter on 227 kHz would interfere with the BBC to an unacceptable degree. It was therefore decided that Westerglen would also operate on 200 kHz.
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The new plan therefore created two "mush areas" – one between Burghead & Westerglen and the other between Westerglen & Droitwich. The BBC took several measures to mitigate this, including very slightly delaying the audio feed to Westerglen to avoid echoes.
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The next measure was to provide a way of precisely locking the phase of the carrier waves of all three longwave transmitters. This is described in this paper:
156/downloads.bbc.co.uk/rd/pubs/report…

Finally, some low-power mediumwave fillers were provided for Radio 4:
- At Aberdeen on 1449 kHz (in the longwave mush area between Burghead and Westerglen)
- In Northern Ireland on 720, Carlisle on 1485 and Newcastle on 603 (in the mush area between Westerglen and Droitwich)
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The new frequency plan was introduced on 23 November 1978. In advance, the BBC distributed stickers for people to put on their radio sets to show the new dial positions of Radios 1, 2, 3 and 4. 158/

https://twitter.com/cl_hart/status/1688650579084558336

The reason why the BBC couldn't take up its 227 kHz allocation disappeared in 1991 when Poland's longwave mast on that frequency collapsed. Two replacement sites in Poland were eventually used, but neither of them put the same strength of signal into the UK.
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By then, Radio 4 was well established on its single longwave frequency of 200 kHz and so the UK did not take advantage of the second LW allocation for broadcasting. Instead, the 227 allocation (which became 225 after 1988) was used for a while in the UK by baby monitors.
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I suspect many parents with these baby monitors didn't realise that their neighbours could use an ordinary LW radio to eavesdrop on their homes.
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That ends this special 1978 instalment of the history of BBC broadcasting on longwave. The next instalment will look at developments between 1978 and 1997.
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