ESR har tidigare publicerat artiklar om PLC i Japan och Tyskland. Diskussionerna om PLC-problematiken pågår för fullt över hela världen. Från Fred Johnson ZL2AMJ ordförande i IARU Region 3 och IARU:s representant för New Zealand Association of Radio Transmitters Incorporated, NZART kommer följande rapport.
IARU at Telecom 2000 show in Hong Kong.
Foto: Copyright © Bengt Falkenberg SM7EQL
Fred Johnson ZL2AMJ, Chairman of
International Amateur Radio Union, Region 3.
Power lines, the Internet, and the future of the HF Spectrum
Information from NZART Council. HQ-info issue 61,October 5 2003
Around the world, the debate is hotting up about PLC (Powerline Communications), also known as PLT (Powerline Telecommunications) and by various other names too. This is the technology that claims to provide broadband high-speed internet services using domestic power lines for the last few kilometres to the home. PLC injects the data signal into the powerline near the electricity substation and it travels along the line to the user.
The problem, of course, is that powerlines are not radio frequency cables. They leak rf energy causing a level of wideband noise in the vicinity of the cable. The mains powerline is a very "noisy" transmission medium, with spikes and other noise, so PLC operators have to use higher injection powers to get their data signals to propagate along the cable. Higher injection powers mean higher emissions, and this is bad news for HF radio operators.
Current proposals in Europe, for example, would raise the level of the background noise level on HF by some 60-70 dB in the proximity of the cable within (3 metres). Further away, the rise would be less, but still considerable.
PLC poses a threat not only to amateur radio! Users of low power devices (for example security systems that tag products in shops) are worried. HF broadcasters are fighting to support sensible emission limits for PLC. The security services privately are worried. But in some countries, government departments involved in security have been told to not object to PLC as the government policy is to support it! Civil Aviation communication and aero-navigation can be threatened by PLC. There are reports of an air accident in Canada being directly attributable to interference from broadband cable systems. And this is only the beginning. New plans for PLC will attempt to use much higher frequencies (beyond 30 MHz even up to 80 MHz) which could immediately pose a threat to some emergency service communications.
One thing is certain. Governments are beginning to realise that there is no compromise here. It is a stark choice between radio communication and internet access. The injection power level being sought by the PLC operators will have a serious and lasting effect on conventional radio communication. If emission limits are set to protect radio, then PLC will find it impossible to operate.
This is an extremely serious issue for amateur radio and for other users of the HF spectrum.
Please be on the lookout for any signs that PLC is being planned in your district. Alone, it is unlikely that amateur radio can fight the supporters of PLC. But if we work with other users of the HF spectrum to build an alliance to protect the HF frequencies there is much more chance of success. That is the challenge for us all.
(The above text was developed from text by Don Beattie, G3BJ, Secretary IARU Region 1)
It's here - PLC is here in New Zealand right now!
A PLC trial in Karaka Street, Takapuna, is known to have taken place in June. Reports are that it had "mixed results". The problem found is that the HF modulation will not pass through the pole-mounted step-down transformers but it worked fine on the low voltage side. Tests over the 400V and 1100V lines gave the same problem. It is understood that development work is being done on a "bypass" to allow PLC data to get around the pole transformers and to use PLC over the high voltage network.
No information has been obtained on whether or not the tests considered the level of HF radiation from the lines.
One application envisaged for PLC by the power company is to automate power-meter reading. For cost reasons, internet service providers may share the system. If one power company is interested in PLC for any purpose, expect others to be interested too.
What do we do about it?
Please keep your local NZART Councillor promptly informed with any PLC information or activity you may observe or obtain. The topic is under intense study both locally and internationally. Further bulletins and reports of actions can be expected.
More information can be obtained from the following websites:
Ovanstående information är inlämnad av Fred Johnson ZL2AMJ, ordförande i IARU Region 3.
The New Zealands administration's position on PLC
Power Line Communications
The Ministry of Economic Development, Radio Spectrum Management Group, has provided this statement to indicate the current New Zealand position on PLC:
The New Zealand situation is essentially the same as Australia.
PLC networks and terminal equipment are similar to Cable TV in that although they are not radio transmitters ("intentional radiators" in the US terminology), they are potentially interfering equipment (i.e. "unintentional radiators") and therefore come within the scope of the EMC framework. The revised FAQ below summarizes the NZ position.
What are the requirements for overhead powerline communications systems (PLC's)?
Overhead powerlines are level 1 'interfering equipment', and any telecommunications on low-voltage lines, and associated terminal equipment, must comply with EN50065-1 or IEC 61000-3-8 as prescribed in the Radiocommunications (EMC Standards) Notice.
Presently, however, there are no specific standards applying to telecommunications over high-voltage lines, and associated PLC terminal equipment. The Ministry will monitor the development of international standards for both. When PLC standards are developed it is likely that the equipment will be required to meet level of conformity 2 requirements.
In the meantime, under regulation 34 of the Radiocommunications Regulations 2001, the Ministry can require PLC high-voltage network operators, and persons installing, supplying or using PLC terminal equipment, to take all reasonable steps necessary to minimise harmful interference to radiocommunications services.
At present customer premises telecommunication terminal equipment (TTE) is required to meet level 3 requirements however this will be changed to level 2 in the near future (in conjunction with Australia under the TTMRA)). The timing for this is likely to be by end of 2003 or early 2004.
If any new relevant IEC standards emerge MED will negotiate with Australia with a view to bringing them under the AU-NZ harmonised EMC arrangements.
The Radiocommunications (EMC Standards) Notice referred to can be found at:
The Australian position, with two explanatory papers, is at:
Ovanstående information är inlämnad av Fred Johnson ZL2AMJ