Speaking at the second annual Powerline Communications Conference in Pretoria recently, the South African Radio League’s (SARL) President Graham Hartlett called on ICASA and the power line communications (PLC) industry to be more transparent when piloting power line communications systems.
“As it stands, power line communication systems spell the death of radio communication ranging from AM radio, to short-wave broadcasting, amateur radio, marine radio and many other essential communication services”, he said.
Radio amateurs are by nature experimenters and understand the need for researching and testing new developments. Much of the work to develop PLC systems is however behind closed doors with little or no interference testing.
Sharing the platform with the SARL, the Amateur Radio Satellite Association’s Hans van de Groenendaal said that the latest tests carried out in the UK showed that current PLC systems are incompatible with radio communications. He cited four areas of major concern:
- Interference to reception of radio signals
- Immunity of PLC systems to nearby RF sources
- Intermodulation products
- Propagation of PLT generated signals via the ionosphere.
The interference of PLC to radio signals has been shown to cover a wide area of the radio spectrum from medium wave to well into the VHF spectrum. While industry has come up with a system to notch out certain frequencies, recent studies by the British regulator Ofcom has shown that it is ineffective in the case of weak signals.
Immunity of PLC systems to strong nearby RF fields has also received little attention if one has to judge by the number of publications on the subject. Radio amateurs would be particularly vulnerable as they live and operate their transmitters in the midst of their community and may be unfairly accused of interfering with their neighbour’s internet or PLC-operated telephone service.
It is ironic that in cases like that there is a tendency to blame the radio amateur for the problem, yet he is licensed to operate on radio frequencies and BPL operators are not! The same would apply to other nearby transmitting stations such as community radio, two-way radio systems used by the police, ambulance and other emergency services.
Intermodulation products are another problem that will have to be researched. Will signals emanating from BPL lines mix with other RF signals to create a large number of unwanted harmonics? It is well documented that harmonics propagate well and are a greater source of interference than the base PLC signals. The possibility of signals being propagated via the ionosphere cannot be excluded. While a search on the internet did not come up with any publications on the subject, the probability of this happening during the solar maximum has been expressed by several scientists studying radio propagation.
Graham Hartlett called on industry and ICASA to work together with users of the radio spectrum and suggested that the following be implemented:
By industry
Pilot studies and PLC trials should include:
- Impact studies on the radio spectrum
- Interference to radio reception
- Increase in local noise floor
- Electromagnetic compatibility of PLC systems with respect to signals generated by radio amateurs in close proximity
- Open communication with users of the radio spectrum
- Disclosure of trial and pilot details
By ICASA
- Registration of all trials and pilot studies
- Monitoring of adherence to current and future standards (ETSI, SABS, radio regulations)
- Ability to stop pilots and trials should inference in the radio spectrum impede operation by radio amateurs and other radio spectrum users
- Develop regulations that will protect users of the radio spectrum against interference from PLC systems.
“There are many well-documented cases that show that current PLC systems are a major problem for radio communication. There is also no internationally accepted standard. The standard issue must be resolved before any further pilots systems are installed” Hartlett said.
Contact Hans van de Groenendaal, SARL, Tel (012) 991-4662, hans@intekom.co.za
