The effects of BPL/PLT on broadcast reception
S. Fleming, J.H. Stott, J.E. Salter
http://www.bbc.co.uk/rd/pubs/whp/whp116.shtml
A visit to Crieff in June 2004 is described, in which measurements were
made to assess the emissions of a Power-Line Telecommunications (PLT)
system and its propensity to cause interference to HF radio reception.
The PLT system was developed by the Spanish company DS2
whose representative unfortunately prevented easurements being made in
a way that was either comparable to tests made on other systems in 2002
or of obvious relevance to normal radio reception. All measurements were
outdoors whereas normal radio reception takes place inside listeners'
homes.
This was unfortunate, especially as DS2 makes claims of significant advances
in reducing interference which it would
have been good to confirm.
Nevertheless it was possible to demonstrate that significant
interference was still caused to reception at the outdoor locations and
it would be reasonable to infer that this would apply with at least equal
force to reception indoors.
The DS2 system had some capacity for inserting notches in the used spectrum
which was explored in the tests. Notching was seen to mitigate interference
substantially in the bands where it was applied.
Some audio recordings demonstrating the effects of interference and the
benefits of notching have been made available for download and are described
in the document.
The measurements, their limitations, and what can nevertheless be inferred
from them are discussed at some length. There remains a clear need to
perform an unencumbered assessment of this PLT system (and any
future ones also claiming improvements in interference mitigation) so
that the threat from PLT to reception of HF broadcasting can be properly
assessed.
From Mike Barraclough
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