Summary
The European regulators' study behind the 173.965-216 MHz entry for assistive listening devices: how analogue FM devices can share the band with digital radio (DAB) and wireless microphones, and how 20 national regulators authorised them in 2014.
Key findings
- Studies analogue FM assistive listening devices with 10 mW e.r.p. and channels up to 50 kHz wide (mostly 25 kHz), used mainly in schools, as candidates for licence-exempt use of unused channels in 174-216 MHz, to relieve congestion in 173.35-175.05 MHz.
- Expects these devices to lose use of spectrum above 173.95 MHz where DAB block 5A is planned, cutting access to some 22 of a previous 35 channels.
- Concludes from measurements that a device should operate at least 300 kHz from the edge of an occupied DAB channel, that it needs a signal-to-interference-plus-noise ratio of about 40 dB, and proposes a DAB field-strength threshold of 35 dBµV/m to protect a DAB receiver 1.5 m away; it gives a site test with a portable DAB receiver at the site boundary, the nearest house and outside a first-floor window.
- States that these devices are secondary and unprotected, cannot claim protection, and must move to other free channels if DAB channel use changes.
- Says wireless microphones in the band (typically 50 mW e.r.p.) tend to interfere with assistive listening devices before the reverse, that the two are usually not used at the same site, and that where they are, a local frequency plan can handle it.
- Observed that the devices' signals stayed "more or less limited to the building" and its close surroundings, and were not noticeable under normal circumstances in neighbouring buildings tens of metres away; where several systems share a building, each is usually run below 10 mW to avoid mutual interference.
- Reports typical installations of 20 to 40 channels and a largest reported installation of 110 channels of 25 kHz, and states that the systems are not expected to become digital in the foreseeable future, because FM's capture ratio allows closer frequency re-use and digital systems add latency.
- In a 2014 questionnaire, 20 administrations answered: 13 used general authorisations up to 50 mW e.r.p., 4 individual authorisations, 1 general authorisation with mandatory registration, 1 a mix, and Norway none; only Denmark and Finland reported an interference case each, one of them at a school for hearing-impaired children, which the respondent put down to bad frequency planning.
Limits
Its scenario is analogue FM in schools, much of it personal systems worn by pupils, rather than venue installations, though the band conditions it proposed apply to both. The measurements were made in one conference room at Ofcom's laboratory in October 2014, with interference judged by ear, by the hearing instrument makers' association. National entries reflect 2014. The executive summary writes EN 300 442 where the body cites EN 300 422. The cover says approved May 2015; the date is the publication date in the ECO database.
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Cite this source
CEPT Electronic Communications Committee (ECC), Working Group Frequency Management. ECC Report 230: Harmonisation possibilities for assistive listening devices in the band 174-216 MHz. European Communications Office (ECO Documentation Database). 22 May 2015. https://docdb.cept.org/document/336 (accessed 9 October 2026).
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