Broadband over Power Lines (BPL) threatens marine distress and safety channels
What is BPL?
Broadband over Power Lines (BPL) is a method of providing broadband internet access to consumers using High Frequency (HF) radio signals coupled into the mains power wiring.
In the BPL system, broadband internet signals are modulated at HF and injected into the overhead power lines. The signals are decoupled from the power lines at the customer's premises.
The downside of BPL
Of course, power lines are designed for carrying high voltage AC at 50 or 60Hz, not HF radio signals. BPL enabled power lines act as large HF antennas, radiating the BPL signals hundreds of metres from the power lines.
Use of the electricity supply network to convey BPL signals will result in the leakage of radiofrequency emissions. This leakage has potential to cause interference to radio communications services.
To achieve the high data bandwidth required for delivery of broadband internet access, the BPL system uses the HF and low VHF radio spectrum from 2 MHz to over 35 MHz. The result is that BPL generates wideband noise over all of HF in the vicinity of the enabled power line. This noise is of sufficient amplitude to mask even relatively strong HF radio signals
BPL is a problem for all HF users
Some radio professionals have regarded BPL as a problem primarily for amateur radio operators.
Although the ITU and IEC are working behind the scenes on BPL, national amateur radio societies like the Wireless Institute of Australia, the American Radio Relay League and the Radio Society Of Great Britain have taken a high profile in opposing BPL.
Of course, BPL is a major problem for amateurs, as they often operate with very weak signals.
However, the wideband nature of BPL means that its emissions are not confined to the amateur HF radio bands. BPL can and does radiate signals on maritime, aeronautical, broadcasting, land mobile, fixed service and military HF allocations.
Some countries (notably Japan) have actually banned BPL because of its proven interference to HF communications. From a technical standpoint, BPL is actually a poor choice for distributing high speed internet. There are more suitable technologies available such as WIFI, fibre and cable.
The situation in Australia
There are a number of BPL trials taking place in Australia at the moment, with the major one being conducted in the Island State of Tasmania
The Australian Government Radio Regulator, ACMA, has developed a set of guidelines for the conduct of BPL trials. These guidelines include the following provision:
Access BPL operators have an obligation to undertake appropriate measures in trialling Access BPL technology to ensure they do not breach the legal provisions of the Radiocommunications Act.
Particular attention must be given to radio communications established for safety-of-life services, police forces or for the safe operation of a vessel or aircraft.
The guidelines then go on to list the specific frequencies to be avoided, including maritime R/T and DSC distress and safety channels.
Unfortunately, monitoring of the Tasmanian BPL trial has revealed that the system is, in fact, radiating signals on the 2, 6, 8, 12 and 16 MHz radiotelephone and DSC distress and safety channels.
These monitoring observations have been passed to the ACMA. Given the potential threat to safety of life, it is hoped that ACMA investigate this problem as a matter of urgency.
Obviously, Maritime Distress and Safety channels are mandated the highest level of protection in the International Radio Regulations, as these channels are used for safety of life at sea purposes.
Moreover, Section 192 of the Australian Radio Communications Act specifically prohibits transmissions which may prejudice the safe operation of a vessel. Heavy penalties are prescribed for breaches of this Section.
So, what is the issue?
Some may argue that BPL emissions on maritime channels do not present a problem unless the effected power line passes close to a coast radio station. However, the fact that these signals are being radiated, in apparent breach of the Government guidelines, can only lead to speculation as to the technical capability of the system provider.
If the signals are not supposed to be radiated now, how can BPL providers guarantee that they will not be radiated from a system which does pass by a coast radio station?
It will be too late to address this problem when a distress signal is blocked by BPL....
One wonders what response ACMA will make to a Coronial inquest into the deaths of mariners who were unable to transmit a distress signal to shore because of BPL interference....
More information on BPL
There are many web sites dedicated to BPL and its problems.
Some of the following sites are primarily written from an amateur radio perspective, however they provide a good technical background on BPL and its potential for interference with all licensed HF radio communications services.
Tasmanian BPL trial reports
Australian Government Radio Regulator (ACMA) BPL page
American Radio Relay League
Wireless Institute of Australia
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