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BBC finds way to reduce its electricity bill by £155k

How can a broadcaster reduce the amount of electricity it uses to transmit a radio station without its listeners noticing?

The BBC, like many other large organisations, has been subject to efficiency savings. In terms of distribution, the BBC is stuck between serving a small, but very vocal group of listeners who still use AM, while working to adapt its business model to cover new digital methods of listening, such on smart speakers and mobile devices. The BBC is one of the last public broadcasters in Europe that is still expected to maintain an AM radio service.

AMC, or AM companding, is currently used on all high-power BBC AM transmitters to reduce electricity consumption. The AMC system reduces the carrier power at high modulation levels, the argument, according to BBC R&D, is that the modulation will then mask any increase in background noise and interference. During the past year, BBC R&D undertook a research project with transmission provider Arqiva to see if the savings could be increased.

Detailed laboratory measurements and listening tests were followed by transmitter and field measurements. Field trials were conducted by Arqiva on the BBC Radio Wales 100kW AM transmitter at Washford and on the 150kW BBC Radio 5Live AM transmitter at Droitwich.

The long-term measurements made at Droitwich indicated annual electricity savings of £86k for the Radio 5 transmitters alone, and £155k if the transmitters for Radios Ulster, Scotland and Wales were to be included. BBC R&D assumed an electricity cost of 10p per unit.

Although the test outcome was positive - audio quality was not affected - the BBC admitted the savings were rather less than predicted from the laboratory work and the initial trial at Washford.

Longer term, AM radio is unlikely to have much of a future, with radio audience research showing an ever greater difference to how listeners under 50 consume audio content, compared to those over 65 years of age. But without any major political push to close down AM radio, any further closedowns will continue on a sporadic basis, where sufficient alternatives are available locally to remove local radio services or when existing transmitter sites would need significant investment to keep services running. Commercial radio services are driven by the market, with Absolute Radio already having pruned AM transmitter sites deemed to be unviable to continue broadcasting from.

Last year, the BBC indicated it would pursue a hybrid approach for radio distribution consisting of FM, DAB and online services.

Details of the  BBC/Arqiva project are available to download from the BBC R&D website.