Subject: [NEXTEL-1] BPL: "A flawed concept." - Avoiding Ham Spectrum with BPL

From: Alan Dixon <[email-masked]>
Date: Sat, 17 Apr 2004 14:09:36 -0400

From:
***************
The ARRL Letter
Vol. 23, No. 16
April 16, 2004
***************

======================================
==>UTILITY ENCOUNTERS MIXED SUCCESS IN 
     AVOIDING AMATEUR SPECTRUM WITH BPL

Amateurs in the Raleigh, North Carolina, area say electric utility
Progress Energy and Broadband over Power Line (BPL) equipment provider
Amperion have had "some success" in their efforts to avoid using Amateur
Radio spectrum on overhead lines in their BPL field trial areas. But
problems persist, and the process is far from quick and simple, says ARRL
North Carolina PIO Gary Pearce, KN4AQ, who has been among local amateurs
closely monitoring the Progress Energy/Amperion BPL trial. Their
experiences could indicate what amateurs may face in areas where BPL is
widely deployed.

"The mitigation process at this iteration of Amperion's hardware is
neither simple nor precise," Pearce said earlier this month. Progress
Energy/Amperion essentially are attempting to "notch out" or completely
avoid ham radio frequencies, since hams have been the only HF users so
far
to file interference complaints. Complicating the effort, he says, is
that
the process is largely hit or miss, requiring field monitoring and
feedback and sometimes another attempt to nail the target.

Pearce says he and Wake County ARES Emergency Coordinator Tom Brown,
N4TAB--an engineer with extensive RF experience--met the week of April 5
with Progress Energy network engineer Bill Godwin at the so-called Phase
II BPL trial areas to review the BPL spectrum in use. Amateurs also
monitored the system using an Amateur Radio mobile station some 75 feet
from the line.

"Bill Godwin had a chart showing where BPL could operate and avoid ham
bands, and Amperion had adjusted its system to comply with that chart,"
Pearce said. Among other issues, Amperion missed the mark on 20
meters--starting a BPL signal block on 14.300 MHz instead of 14.350 MHz,
he pointed out.

Pearce attributed the problem to a likely error in calculating the
spectrum needed. BPL spectrum block edges "are not brick walls," he said,
but taper off, with progressively weaker carriers remaining audible up to
100 kHz away, depending on the noise floor. "The remaining signals are
very weak but would bother a home station within a city block or two of
the power line." The goal is to be able to place BPL on a line in the
immediate vicinity of a ham.

Unclear at this stage is whether the "notching" scheme will work in a
more-dense BPL environment. "More spectrum can be used below 7 and above
30 MHz, but Amperion prefers to remain between 7 and 30 MHz," Pearce
said.
"If this spectrum can be rotated between line segments, and the notches
can be deepened some, they may satisfy the concerns of hams for the
Amateur Radio spectrum." But, he adds, no efforts are under way to avoid
other shortwave frequencies.

"We appreciate this proactive attempt," Pearce said. "We will point out
again that there are other public uses and users of the spectrum in
between the ham bands." Amateur Radio operators "cannot sit back and say,
'Well, our problem's solved. Good luck with yours!'" Pearce says.

He says that for this reason alone, the North Carolina amateurs still
consider BPL a flawed concept. And, while he credits Progress Energy and
Amperion with cooperating to resolve amateur interference issues
piecemeal, "we just want to make sure that everyone understands where the
goal line stands."

======================================
The ARRL Letter is published Fridays, 50 times each year, by the American
Radio Relay League--225 Main St, Newington, CT 06111; 
tel 860-594-0200; fax 860-594-0259; <http://www.arrl.org/>. 
Jim Haynie, W5JBP, President.

Material from The ARRL Letter may be republished or reproduced in whole
or
in part in any form without additional permission. Credit must be given
to
The ARRL Letter and The American Radio Relay League.

==>Editorial questions or comments: Rick Lindquist, N1RL, [email-masked]

==>How to Get The ARRL Letter
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