k4kyv
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Don
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« on: April 02, 2006, 09:31:19 PM » |
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From this week's ARRL LETTER:
ARIZONA BPL FIELD TRIAL ENDS
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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