[Swprograms] BBC R&D- Effect of PLT on broadcast reception

[Mike Barraclough <softbulletin1@xxxxxxxxx>]

Two recently published papers online:

Co-existence of PLT and Radio Services ? A
Possibility?
J.H. Stott

http://www.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP114.pdf

Power Line Telecommunications (sending data over mains
wiring) unfortunately gives rise to unwanted emissions
that can interfere with the operation of radio
services, currently predominantly those in the HF
range used for long-distance radio communication.
Setting a simple emissions limit is bound to fail: no
level exists which could permit PLT to operate while
also protecting radio services. PLT and radio services
simply cannot operate at the same time, in the same
part of the spectrum, in the same place.

But that does not mean that co-existence is
impossible. One possible solution is for the PLT
system to avoid using parts of the radio spectrum that
are locally occupied by radio services. This paper
discusses such a possibility, including some
experimental results that support its feasibility.

The effects of power-line telecommunications on
broadcast reception: second trial in Crieff
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 measurements 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.

Mike






		
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