"Hams" wrote in message
...

http://www1.commsworld.com.au/NASApp...=commsworld/ho
me&var_el=art&art_id=1034683529903&var_sect=NEWS&f rom=home

http://tinyurl.com/jpua

NEWS



HAMS' HIGH TENSION OVER POWERLINE - 12 August 2003
Richard Chirgwin

Stray Signals Spoil Spectrum


Amateur radio operators in America have conducted tests which they say
demonstrate unacceptable radio interference caused by powerline broadband
systems.

The ham radio operators conducted tests in four US states where powerline
is in
pilots, and the results of those tests were presented at the group's
Austin
Summerfest earlier this month.

The tests demonstrated that powerline broadband systems using frequencies
between 2Mbps and 80Mbps created wide-spectrum interference on HF and
low-VHF
amateur radio allocations.

The test was conducted by the laboratory manager of America's ARRL (the
American
Radio Relay League), Ed Hare, who tested spectrum measurements in
Maryland,
Virginia, Pennsylvania and New York. He is quoted in the ARRL's online
publication as saying that interference "ranged from moderate to extremely
strong". In some tests, powerline interference was propagating for miles.

The tests found three types of interference: static, pulse noise, and
"warbling". The interference was detectable both from overhead and from
underground cabling.

The ARRL had already filed technical exhibits to an FCC powerline inquiry,
and
says it will file further comments this month.

The ARRL article can be found here.{ Http://arrl.org/ }
CommsWorld Comment:

The first trials of powerline technology during the 1990s were killed off
by
interference, and by overhyped vendor claims. When powerline started to
make its
comeback, the vendor community put its hand on its collective heart and
promised
that interference was solved.

If the ARRL's tests are right - which is a reasonable assumption given the
demanding nature of a ham radio license - then powerline vendors were
mistaken
about interference.

This is hardly surprising. The physical parameters of an electricity
distribution network vary much more widely than anything you'll see in a
laboratory. It's quite likely that the interference seen in lab tests was
small
enough to convince the industry the technology works. But out in the
field,
there's plenty of things to fool around with the line impedance.

This could have been foreseen. If the powerline vendors were wrong about
interference, can we trust their claims about speed, performance, and
cost?

It's easy to trivialise the concerns of the ham operators - and that is
exactly
the tack utilities are taking in America. But ham operators aren't
ignorant; and
they're not without rights. In all countries, ham is licensed - and that
means
the operator has paid a fee for the right to use spectrum.


For anyone that don't believe it yet go to the ARRL web site and download
the 24mb file and see for yourself. It is beyone belief.

Dan/W4NTI