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MikeB
28-01-2006, 11:18
The editorial in the latest EBU technical review is entitled spectrum efficiency, it says in paragraph 8:

"So where does this leave the concept of spectrum efficiency? First, we must acknowledge that measuring spectrum efficiency in bit/s/Hz is inadequate and inappropriate. Secondly, we need to extend the definition of spectrum efficiency to take account of other factors, such as transmitter powers, the overall cost of networks and, crucially, the potential for interference to (or from) other services."

and goes on to discuss the effect of interference on digital systems from licenced and unlicenced sources and includes this quote on DRM:

"One regulator personally told me that the objective of extending the use of broadband access to the Internet was politically far more important than the need to protect old-fashioned AM radio services (especially in the HF bands) – but he was surprised to learn that Digital Radio Mondiale has spent a huge amount of time and money developing a new digital radio system to operate in these bands."

It's an interesting read and I have two questions:

1. What level of interference will give rise to DRM on MF and HF dropping out relative to its signal strength, does the interference have to be stronger than the DRM signal? Are some types of interference more troublesome than others?

2. In the UK I have always, perhaps too optimistically, taken the view that broadband over power lines will not prove commercially viable, basically as other systems have taken the market and it would require a heavy investment by the power companies. There have been tests by two companies at Crieff but no announcement of roll out nor any real marketing of HomePlug or similar power line networking devices mentioned earlier this year by BBC Click Online:
http://news.bbc.co.uk/1/hi/programmes/click_online/4080566.stm
Am I correct in this assumption and is the technology likely to be commercially viable in Germany, France, the Benelux and other parts of Europe DRM is initially targeting?

The EBU Technical Review editorial is at:
http://www.ebu.ch/en/technical/trev/trev_305-editorial.html

Mike

jbriggs
13-02-2006, 10:29
In addtion to the tests counducted by the BBC that Mike mentions, Full test report, see paper 67 (http://www.bbc.co.uk/rd/pubs/whp/index061-080.shtml) Austrian measurements also confirm that PLC causes HF interference The Austrian government has published a report about disturbances caused by Power Line Communications (PLC) in the HF bands (2000-30000 kHz).

In Austria, broadband services via PLC are being provided in one region (approx. 250,000 inhabitants). Since the first trials of this technology in this region, which commenced in 2001, radio amateurs and various public safety organizations periodically reported disturbances in the frequency bands below 30 MHz, which were, according to the opinion of the spectrum users, caused by PLC operation in the concerned region.

In order to verify the complaints of the various spectrum users, the competent Austrian authority (the Federal Ministry for Transport, Innovation and Technology, Telecommunications Authority) investigated the reported disturbances. The measurements carried out in May 2004, April 2005 and November 2005 clearly showed that the cause of the disturbance reported by users of the HF band in the concerned region is the operation of PLC. In particular, the measurement proved that the emission of PLC installations is up to 16,000 times (42 dB) higher than the relevant limit (according to CEPT ECC/REC/(05)04). Details of the measurement results are available in the annex to the following document (in German and English):

http://www.bmvit.gv.at/telekommunikation/publikationen/downloads/inf022005v3.pdf