Cellular carriers are bringing more equipment to Central Oregon for the Aug. 21 solar eclipse, but no one knows how networks will perform when 200,000 visitors converge on Central Oregon.

The eclipse is expected not only to draw huge crowds to remote areas such as Madras, population 6,729, but it could be one of the most widely photographed and shared events of the internet era. While the carriers say their networks should handle the data demand, one expert said service levels will vary from location to location.

“Some areas are going to have enough coverage. Others are going to be like a 1990s AOL experience,” said Don Gilbreath, systems vice president at Rajant, a Philadelphia-area company that creates private wireless networks.

Whether consumers can upload to Instagram with ease or struggle to make voice calls will come down to several factors, Gilbreath said. First is the strength of the existing network, and that depends on the size of the everyday population, he said. It’s reasonable to expect congestion in rural areas swollen with tourists, he said.

Carriers like Verizon and AT&T are used to adding capacity for huge events like a concert or the Super Bowl, Gilbreath said, but the eclipse will test those systems because no one knows for sure how many people will show up.

Then there’s the question of what kind of data people will try to use and whether the demand will hit all at once. The recent derailment of a freight train in Hyndman, Pennsylvania, is a classic example of how easily networks can jam, he said. “It was so bad police couldn’t even talk to each other,” Gilbreath said.

First responders in Central Oregon are concerned enough about emergency communications that they’ve contacted ham radio operators for backup and created lists of working pay phones. But the major wireless carriers are not expecting failure.

“We expect customers to be able to use their phones as normal during the eclipse,” AT&T network engineer Tara Jansen said through a spokeswoman.

AT&T and Verizon are bringing mobile antennas, known as cells on wheels, or COWs, to the Jefferson County Fairgrounds in Madras, which is home of Solarfest. AT&T says its cells on wheels will boost capacity in the area by “200 percent.” The company would not elaborate on its existing capacity for competitive reasons. Likewise, Verizon declined to say exactly how much capacity will be added in Madras and Bend, where it has added three low-visibility antennas to the top of city hall.

Verizon has also added capacity to “numerous” existing cell sites in Bend and Madras, spokeswoman Karen Schulz said.

Verizon customers might have already noticed slower service during large events in downtown Bend. City officials have been asking Verizon to increase network capacity downtown for some time, and with the eclipse coming have agreed to host the antennas at no charge, city spokeswoman Anne Aurand said.

The town of Mitchell, which is near the Painted Hills off U.S. Highway 26, also received some much-needed cell coverage as a result of the eclipse and lobbying by residents and U.S. Rep. Greg Walden, R-Hood River. Despite its proximity to a trucking route and tourist destination, Mitchell is a dead zone, where not even emergency calls are possible from a cellphone, said resident and volunteer ambulance driver Kiefer Davis.

Tourists — who could number in the tens of thousands for the eclipse — usually are caught off guard by the fact that they can’t get a call out when something happens on the highway, Davis said. “They’re actually in a high danger zone from Prineville all the way to Dayville,” he said.

AT&T set up a mobile unit in Mitchell two months ago. Jansen said the mobile unit will stay in Mitchell “for the time being” but could be called away for use in a natural disaster.

Other carriers are taking similar steps to ensure a good experience for customers. U.S. Cellular is adding capacity and fine-tuning towers in Madras and Bend, Tim Brown, director of operations in the West said through a spokesman.

“At large events such as this, we usually see a spike in text and data usage more than voice, so we are also looking at how we can prioritize those services that are most important to our customers,” Brown said in an emailed statement.

Rich Roche, director of external affairs at AT&T, visited Madras on Wednesday to talk to media about the mobile unit and network capacity. Asked what customers can realistically expect, he said, “The hope is with the COW out there… traffic will be able to be managed.” He added, though, that at times, it might take longer to send data, so customers might hold off on social media sharing until after the event.

Roche also pointed out that text messages travel more quickly through the network than voice calls, though texts can mean additional charges.

—Reporter: kmclaughlin@bendbulletin.com, 541-617-7860