Towering feats of engineering

Ten miles north of Blackduck, Minn., an area called Busy Corner is not so busy. It’s pretty darn silent, save for the twang of tensioned cable guy-wires that’s as crisp as the cold.

Twenty degrees isn’t so bad for a northern Minnesotan, but for the men who are nearly 200 feet up in the brisk air – halfway through constructing a nearly 400-foot microwave tower, somehow dexterously tightening nuts and bolts – cold is cold.

From the solid ground below, Minnkota Telecommunications Engineer Eric Bergman is glad his side of the project is more signals and circuits and less harnesses and hard hats.

“You couldn’t pay me enough to do it, so bless them for doing that,” said Bergman, eyes to the sky. He led the site design, licensing and material orders for the project, one piece in a plan to take Minnkota’s telecommunications system from the analog past to the digital future.

The current project scope includes 11 “hops” – or connections from tower to tower. Work began in May 2018, with a goal of wrapping the initial phase by October 2019.

Busy Corner is the first guyed tower in Bergman’s portfolio.

“This is a learning process for me,” he said. “I’ve done a couple of self-supporting towers, but I’ve never seen how they string the guy-wires and lift each section at a time. It’s interesting to actually see it instead of being behind a desk.”

Going up

Over the span of a couple of weeks, the contracted construction crew hoists and assembles 20-foot sections of the tower, stringing and tightening guy-wires one elevation at a time. Once the tower is erect and stabilized to massive underground cement anchors, the team affixes the dishes, antennas, lights, strobes and other equipment. Then it’s time to run lines down to the brand new control house, where the Minnkota crew enters the game.

Communication technicians mount and wire radios in the control house and connect them to the tower lines. The signal is then tested at the next tower in Bemidji.

“We’ll actually have someone up on the tower, turning and tuning the dish – just like at your house, trying to get the TV rabbit ears to work. It’s just a little bit higher up,” Bergman explained.

As soon as the new tower goes live, the old structure next to it can be taken out of service and deconstructed, likely in early 2019. That will kick off four to five more tower projects that will continue through the fall, many that have been in the queue for several years.

“It’s nice to see traction on some of these projects,” Bergman said. “This is a good warm up for the rest of them,” he added, the irony of the phrase cracking a grin on his wind-pinkened face.

A tall order

At 390 feet, the Busy Corner tower is the tallest in Minnkota’s microwave communications system. The network comprises a combination of more than forty guyed towers (supported by anchored guy-wires) and self-supporting towers.

The telecommunications system is used primarily to send real-time information from Minnkota’s substations to the power system operators in Grand Forks, allowing them to operate the entire power grid over a private network. With this infrastructure, Minnkota can avoid reliance on outside entities to carry that critical traffic.

The system is also used for coordinating line trips, opening and closing breakers, monitoring power flow, and supporting mobile radio traffic and other essential communication. All these connections need to be made reliably – and fast. “We’re talking milliseconds,” specified Telecomm Engineering Supervisor Todd Bommersbach.

In order to keep the 50-year-old system running as quickly as it needs to, engineers and operators need to have the latest technology. That need spurred the largest microwave project Minnkota has tackled in one shot.

“A lot of our equipment in the field is analog-based – not digital. So we’re missing out on a lot of technology capabilities in about half of our system,” Bommersbach explained.

Bergman added that with this new digital tech, Minnkota needs bigger dishes, or more dishes, on its towers. “A lot of times, the towers were not originally designed for that,” he said. “We’ve evaluated the existing towers, and where needed, we’re putting up a new tower to handle that additional loading.”

Nearly every tower in the system will eventually need to be replaced, reinforced or upgraded, in phases that will continue beyond the project’s initial scope. That means many more chilly site visits for Bergman and his telecomm team.

“If I don’t come out here, I don’t get to see what it turns into,” he said during a quick warm-up in Busy Corner’s 72-degree control house. “It’s great to see some of the challenges they have when they put the tower up. It makes it a little easier for the next project like this to have more relevant, real-world experience.”