Arizona BPL Field Trial Ends

The Cottonwood BPL field trial used Mitsubishi Electric PLCLINK equipment. [Bob Thompson, KC8BOB, Photo]

NEWINGTON, CT, Mar 28, 2006--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 FCC Part 5 Experimental license WD2XMB, went silent this month. The Part 5 license, renewed last November, 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 experimental operation in Cottonwood and moving it.

"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."

Shipton said MTI indicated to him on March 14 that it had some new chipsets offering more bandwidth but, given various technical roadblocks it had encountered in Cottonwood, was considering shifting the site of its BPL experiments to the Phoenix area, where MTI is headquartered. Not only did amateurs determine the system was generating interference on the high end of 20 meters and elsewhere, Shipton reported, VVARA showed 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."

Getting Out of Dodge

Bob Shipton, K8EQC, chairs the VVARA BPL Committee and is the club's vice president. [Ernie Cummings, K6XF, Photo]

VVARA BPL Committee member Mike Kinney, KU7W, assists in interference testing of the Cottonwood BPL system. [Bob Thompson, KC8BOB, Photo]

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 his committee's experience with the MTI BPL system--initially operated by Electric Broadband LLC--has involved a lot of work, Shipton said he's pleased with the outcome.

"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. It's not known at this point."

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. "All I know is that our efforts as a radio club, as the Verde Valley Amateur Radio Association here in Cottonwood--and a lot of Prescott hams were involved in this--may have been instrumental in getting them to realize that if they're going to do their testing, maybe they need to have it closer to home."

The VVARA's efforts over the lifespan of the Cottonwood BPL experiment "raised issues and raised questions," Shipton said, to the point that representatives of Mitsubish--the manufacturer of the system's BPL equipment--"went back to Japan to try and sort some of this out." In fact, he noted, once MTI started masking amateur spectrum, its efforts were quite effective.

"Whether, had they pursued that further, whether they would have gotten rid of all the interference to amateur operations, I don't know. They had not gotten rid of all of it."

Interference Bad, Noise Worse

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.

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 a "raspy, buzzing" noise. "There were times when it was below S9, but it was very irritating trying to listen to amateur communications."

MTI's Part 5 license permitted experimentation from 2.46 to 38 MHz. The pilot system could not have anymore than 10 "customer premise units" at any given time. Shipton estimated that there were only a handful of users online, including a school, and he said the fact some customers had moved away may also have been a factor in MTI's shutdown decision. The system extended along some 1500 feet of overhead power line in Cottonwood, located in Yavapai County. The service area included no Amateur Radio fixed stations.

A Lesson for BPL Providers?

Interference on segments of 20 meters was S9 or better and as strong as 20 dB over S9 on the high end of the band. [Bob Thompson, KC8BOB, Photo]

Overall, Shipton said, he believes that 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. MTI, he said, indicated to him that it would be looking at other brands of equipment if and when it pursues BPL testing in Arizona.

"The issue of ham interference was one issue on their plate out of many, many issues," he said.

Litany of Complaints

The first Amateur Radio complaint, filed in June 2004, cited VVARA testing at HF asserting that BPL interference made attempts at ham radio communication useless. VVARA submitted a lengthy and comprehensive report to the utility, the BPL operator and the FCC the next month detailing interference issues.

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 with which then-operator Electric Broadband had told the FCC it would comply.

The League's second shutdown request in October 2004 accused the FCC of doing "absolutely nothing" to enforce its rules or to protect licensed services from interference.

For additional information, visit the "Broadband Over Power Line (BPL) and Amateur Radio" page on the ARRL Web site. To support the League's efforts in this area, visit the ARRL's secure BPL Web site.

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