Shotgun wedding

Whenever a storm or accident causes a power outage after hours in northeast Nebraska, at least four members of the Northeast Nebraska Public Power District’s duty crew are ready to respond.

When a power outage call comes, the utility’s toll-free telephone number automatically feeds the call over the radio to the four duty crew members who can determine immediately who is closest to the trouble and what response is required. Instead of returning to the home office in Wayne, Neb., they can make plans to resolve the problem over their radios.

“That method works, but not as well as we want,” said Mark Bressler, the load management supervisor for NNPPD.

To improve the power company’s mobile communications and lay the foundation for a radio network to include other Nebraska power companies — and enable interoperable radio communications among them — Bressler has contracted DX Radio Systems, Sun Valley, Calif., to build a 220 MHz radio system for the electric cooperative.

NNPPD is installing a three-site, four-channel system using “extremely narrowband” FM and MPT 1327 trunking. MPT trunking is a digital format that uses analog voice. With only 30 units on the system, it’s small, but Bressler envisions building a larger network to achieve radio interoperability with other Nebraska electric utilities.

In fact, the project has its roots in an effort to bring radio communications together between NNPPD and another power district when they merged four years ago. One of the districts uses VHF, the other, 800 MHz. Bressler saw using 220 MHz as a way to bring them both together.

The power district measures 90 miles east to west and 50 miles north to south. A central station at the company headquarters in Wayne ties together three remote sites with dispatch and data communications.

With only four channels per site, why did NNPPD choose trunking? Bressler said that an ability to pass data and the future option for vehicle location and automatic meter reading led to the choice of equipment with MPT 1327 trunking, which can support those applications.

“The radios have data ports and display screens so the dispatcher needn’t call until the truck operator can be reached. Instead, the dispatcher can leave a message or a job order on the display. When the truck operator returns, he doesn’t have to call in,” Bressler said.

“In the state of Nebraska, the Midplains Energy Services Alliance, a company formed by the Nebraska electric cooperatives, has purchased frequencies in the 220 MHz band, and we’ll use some of those. If this new, cutting-edge radio system looks and works as well as it is supposed to, we will try to get the rest of the Nebraska electric cooperatives to consider building similar systems. Then we would have interoperable radio communications with our neighboring districts,” Bressler said.

Bressler explained that the process of workers throwing switches on transmission lines that run from one district to another would be facilitated with interoperable radio communications. He explained that switches need to be thrown under both normal and stormy conditions. Previously, the worker would call the office and communicate with other workers through the regional dispatcher. With the 220 MHz system, the workers would have a direct link.

“The line worker in the truck has to notify the office to throw the switch. We have switches in both 115 kV and 69 kV substations. As yet, they cannot be operated remotely by our workers, and have to be operated remotely by our power supplier, Nebraska Public Power, from its dispatch center in Doniphan, Neb. Even then, steps have to be taken by someone standing in front of the switch panel. Sometimes the switching process involves two or three trucks,” Bressler said.

Another advantage of the new 220 MHz system stems from the microwave system used to link the sites. The microwave will carry system audio, data backhaul and billing data between the billing center and the general headquarters in Wayne. In the future, Bressler said, automatic meter reading would tie it all together.

Sharp, a senior systems engineer with DX Radio heads the turnkey construction project for the NNPPD.

“This project has a long history. NNPPD became interested in 220 MHz trunked radio four years ago when the National Rural Telecommunications Cooperative started selling Securicor Wireless products,” Sharp said. (See “Behind the Scenes At 220 MHz” inside this article.)

At the time, Sharp and other DX Radio employees were working for Alexander Utility Engineering, San Antonio, Texas, where they were engineering 220 MHz systems for various utilities that participated in the NRTC program.

“We’re trying to follow up on the interest in 220 MHz and trunked radio in general that NRTC had generated a few years ago,” he said.

“The NNPPD system got delayed because of Securicor’s inability to supply a hand-held unit. The power company needed telephone interconnected portables for nighttime dispatching. Once the portable became available, it was found to work poorly. And then, Securicor fell apart,” Sharp said.

Sharp added that AUE had looked at the possibility of DX Radio providing the infrastructure, designed and manufactured by Fylde Microsystems, Blackpool, Lancashire, United Kingdom.

Brian Seelde, director of Fylde Microsystems, said that both systems from Securicor Wireless and DX Radio Systems use the MPT open standard.

“Securicor chose a novel modulation system called ‘linear modulation.’ This technology was, like many, a step too far. It worked OK in the laboratory, but in the field, it had many problems that just could not be solved,” Seedle said.

Seedle was one of the authors of the MPT format, and he said that it is “the global leader for open trunking standards. It offers a price/performance ratio that cannot be matched by any other standard. The MPT standards are free and can be downloaded from many sites on the Internet, including www.fyldemicro.com or the U.K. government site at www.radio.gov.uk.”

For subscriber units, DX Radio Systems supplies units made by ADI Communications, Taichung, Republic of China, under the direct control of TMC Radio, Melbourne, Australia. In April, TMC Radio purchased the intellectual property and manufacturing rights of Simoco’s SRM9000 mobile and SRP8000 portable series of conventional and MPT 1327 products. DX Radio Systems has exclusive rights to the TMC Radio units in the United States and Mexico to sell them under the DX Radio name.

When Sharp went to work for DX Radio Systems, he suggested to Bressler that NNPPD consider finishing its project using the DX Radio 220 MHz FM trunked radio products.

What’s unusual about DX Radio System’s technology is that the FM signal is confined to less than 10 kHz bandwidth, somewhat less than the narrowband standard of 12.5 kHz. This channel bandwidth plan extracts more usable channels from the available channel blocks than the wider bandwidth does, when a licensee aggregates the original 5 kHz channels to work with FM.

“There is no defined emission mask for the narrowband products at 220 when you aggregate bandwidth and lay out your own channel plan. The only requirement is that you protect adjacent channel blocks in the same manner as an emission mask F would do, if it were used. We’re using 1.6 kHz deviation. You lose some signal-to-noise ratio as the modulation index goes down, so there is a slight degradation on range, but it is not that noticeable,” Sharp said.

He said that the NNPPD system is DX Radio System’s first turnkey project built for the customer as a usable, operational product. But the company already has been operating two test systems, one for a year, and another for six months, for utility customers.

Sharp said that the system is MPT 1327-compliant with integrated voice and data, and PSTN and PABX connectivity. Access to the radio channels by users can be controlled with various levels of priority, allowing the system owner to tailor it to fit traffic requirements.

The system also supports pre-emptive emergency calls, so if a user is in trouble, he is guaranteed access. Another user would be thrown off to connect this type of call.

The system allows placing wide-area group calls. Sharp said that, in the United States, “people want to emulate party-line radios, so they do group calls rather than radio-to-radio calls.”

As for MPT 1327 acceptance, he said “there more MPT 1327 systems on the planet than all trunked radio systems combined, but they’re all outside the United States.”

Sharp said the NNPPD might install AVL in six months to a year.

Moreover, once mobile data terminals are installed in the power company’s trucks, the utility is planning some other data applications, such as remote job entry.

Although NNPPD is working with a software vendor that supplies turnkey software for coops, the utility hasn’t yet selected an MDT vendor.

Sharp said that a lot of electric coops are building independent voice and data systems to replace antiquated equipment. He described them as mostly conservative organizations that prefer a proven technology; thus, he sees their next move as involving trunked systems.

“These systems fit their unique requirements, including data. Their radio systems go underutilized most of the time, until there is an outage or emergency. Then they carry extreme traffic levels where only trunking can handle the multiple calls and groups,” Sharp said.

With MPT 1327 as an open standard served by 31 manufacturers of subscriber units around the world, Sharp said that NNPPD is putting in infrastructure that is unique to its manufacturer, but the utility can use any subscriber unit that is MPT 1327-compliant.

Bressler has gone through the 220 MHz experience once already with NRTC and Securicor and found his project stalled because the portable radio product first couldn’t be delivered when promised, and once delivered, didn’t work as well as he needed it to.

Although he recognized a certain degree of risk with 220 MHz, he said, “We’re comfortable with DX Radio Systems, and the Simoco [TMC Radio] mobile and portable products. There’s risk, but it’s worth taking.”

At DX Radio Systems, Bill Cody, the company’s operations manager, said, “We’re looking forward to ‘kicking butt’ with MPT 1327. We’re working with a lot of the coops. And the NNPPD system is being staged in L.A. right now.”

Behind the scenes at 220 MHz

Northeast Nebraska Public Power District started its 220 MHz effort four years ago through a program offered at the time by the National Rural Telecommunications Cooperative, Herndon, Va., and a radio manufacturer, Securicor Wireless, New York. The program was intended to supply electric utilities with radio frequencies for statewide operations, together with equipment and a plan for using the frequencies both for a utility’s internal communications and for airtime sales to other users as a profit-making enterprise.

NRTC’s three-pronged program — frequencies, internal communications and airtime sales — failed to gain widespread acceptance and dwindled away. Most utilities that built systems with Securicor Wireless equipment eventually dismantled them.

Although NRTC no longer encourages its members to sell airtime and it no longer promotes two-way radio equipment sales, its members still can purchase the rights to use 220 MHz frequencies through the cooperative.

Several manufacturers are offering equipment options, but now utilities make their own equipment arrangements without NRTC involvement.

“We primarily support the utilities’ internal communications,” said Bill Saul, NRTC’s director of wireless systems. “The only thing we’re promoting is to use 220 MHz frequencies to support their core business, which is telemetry for SCADA or automatic meter reading, or two-way radio dispatch for their fleets.”

Saul said that NRTC has licenses available for single-site, paired channel systems.

“We don’t promote anyone’s equipment, but we know that Microwave Data Systems offers 220 MHz equipment for telemetry.

For two-way radio systems, Tait Mobile Radio has an FM product with a number of capabilities, both conventional and MPT 1327 trunked, and Motorola has announced an FM 220 MHz two-way radio product with LTR and PassPort trunking,” Saul said.

Microwave Data Systems is in Rochester, N.Y. Tait Mobile Radio’s North American office is in Markham, Ontario, Canada. Motorola’s headquarters is in Schaumburg, Ill.

DX Radio Systems, Sun Valley, Calif., offers conventional and trunked equipment on all frequency bands, and the “extremely narrowband” FM, 220 MHz, MPT 1327 trunked radio equipment.

Another manufacturer, BizCom, Fort Lauderdale, Fla., offers amplitude-companded single-sideband conventional and trunked two-way radio equipment designed for the 220 MHz frequency band’s original 5 kHz channels.