Andre Kesteloot andre.kesteloot at
Sat Apr 1 08:55:30 CST 2006

==>From the ARRL Newsletter

A BPL field trial in Cottonwood, Arizona, that drew complaints from Amateur
Radio operators from 2004 until earlier this year apparently has shut down
for good. The small system, which Mountain Telecommunications Inc (MTI)
operated under an FCC Part 5 Experimental license WD2XMB, went silent in
early March. The Part 5 license stipulates that the company "establish and
maintain" a relationship with the Verde Valley Amateur Radio Association
(VVARA), which called for the system's shutdown as recently as last
December. According to VVARA BPL Committee Chair Bob Shipton, K8EQC, MTI
initially took the system down for a firmware upgrade but subsequently told
him that it was discontinuing the experiment in Cottonwood and moving it,
possibly to the Phoenix area, where MTI is headquartered.

"There's no definitive statement from Arizona Public Service or Mountain
Telecommunications that they have stopped BPL in the state of Arizona
entirely," Shipton told ARRL this week. "It's just that they pulled out of
the Cottonwood area." 

Not only did the VVARA determine the system was generating interference on
the high end of 20 meters and elsewhere, Shipton said, the club demonstrated
that it could "break" the system's datastream while running as little as 65
watts from a mobile station.

"I think that was a bit of a surprise to them," allowed Shipton, who noted
that MTI remained helpful and lived up to its agreement to keep the VVARA in
the loop. At the same time, he said, MTI learned everything it wanted to
learn in the Cottonwood area, "and they know we're not going to let this
thing go."

According to club measurements made in cooperation with MTI, the BPL
interference in the vicinity of the system on the upper end of 20 meters was
20 dB over S9, Shipton said, and even in the middle of the band, it was S7
to S9. "On 17 meters, from 18.059 to 18.180 they were S9, on the 15 meter
band they were S7," he added.

In support of the VVARA effort, the ARRL twice asked the FCC to shut down
the Cottonwood BPL field trial for interfering with Amateur Radio
communication. The League's own testing of the Cottonwood system in the
summer of 2004 indicated "extremely high" levels of radiated RF energy on
amateur HF allocations--well in excess of the FCC Part 15 levels.

Beyond the mere fact of the RF interference, Shipton continued, was the
nature of the interference itself. "With the high-speed chipsets, the sound
is so obnoxious that you don't necessarily have to have a lot of RF strength
on an S meter to cause interference when you're trying to listen to a
station--even if it's stronger," he said, describing it as an annoying
"raspy, buzzing" noise.

In December, the VVARA filed with the FCC what Shipton characterized as an
"informal" interference report of ongoing interference on 20, 17 and 15
meters and reiterated its request that the FCC shut down the system. While
MTI's interactions with the VVARA may not have been the primary factor in
its decision to take its BPL pilot elsewhere, Shipton believes his club at
least played a role.

"We feel at least we got 'em out of Dodge--they're out of Cottonwood," he
said. "What they do in Phoenix will have to be taken up by the Phoenix
amateur operators, if they do anything."

Shipton said he believes efforts like those of the VVARA to raise the
interference issue and keep it before the public are prompting the BPL
industry to take a harder look at how to avoid the problem altogether. "The
issue of ham interference was one issue on their plate out of many, many
issues," he said.

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