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Date: 6 February 2003
Dear
During the spring of 2002 the Radiocommunications Agency (RA) sought views on relaxing the limits set in the measurement standard MPT 1570 (August 2001), to control potential interference from telecommunications systems such as DSL and Power Line Technology (PLT), operating on frequencies between 9kHz and 150kHz. Including your response the RA received 10 responses to this consultation. The background of why regulations are necessary are set out in our letter of 10 June (copy attached) asking for views on relaxing the limits.
Two of the responses were from radio users. One sought an adequate level of protection for amateur users. The other highlighted the possibilities of interference to 60 kHz radio controlled clocks used by some commercial radio broadcasters. The other responses, mainly from DSL and PLT providers, generally supported a relaxation of the limits set in MPT 1570 (August 2001). As a result of this consultation Ministers have agreed to relax the limits set in MPT 1570 (August 2001). In doing so, it was noted that there is a slight risk of interference to 60kHz radio controlled clocks but it was felt that this risk was sufficiently small as to be acceptable. A copy of the new standard, MPT 1570 (January 2003) is enclosed for your information.
The amended MPT 1570 (January 2003) has raised by 7dB the limit curve at frequencies between 9kHz and 150kHz. The 7dB change is derived from two changes. The change of measurement distance to 3 metres from 1 metre has the effect of reducing the expected signal level by 9.5dB. The change in limit to mimic the measurement bandwidth above 150kHz, of 9kHz, has the effect of increasing the limit by 16.5dB. The addition of -9.5dB and +16.5dB raises the limit curve by 7dB.
Additionally, measurement by averaging over time has been introduced in place of peak reading measurements. Low data rate low frequency systems produce signals that are not broadband and do not present risk of undue interference to radio services. Indeed, averaging may be the only practical method of measurement, where the time between the transmission bursts exceeds the sweep time of the measurement instrument.
NM510
The Wireless Telegraphy (Control of Interference from Material Substances forming part of Telecommunication Systems) Regulations 2003 are now being finalised and will be laid before parliament very shortly.
The Radiocommunications Agency is grateful for contributions from interested parties on this matter.
Yours sincerely
NEIL MARR
Enforcement Policy Manager
NM510