Clam Lake's Cold War E.L.F. Transmission Site

Jun 8, 2020

Did you know about the Cold War era ELF transmission site at Clam Lake, 80 miles northwest of Rhinelander? In this week’s Wildlife Matters, the Masked Biologist tells us about the antenna array and its connection to wildlife management.

Recently I was telling my wife about the ELF antenna array and its current value, and for some reason I was surprised that she had never heard of it. So, I thought maybe it would be a good topic for today’s episode of wildlife matters.

At the end of WWII, the use of submarines was becoming increasingly important for the United States and its military presence around the globe. As we moved further into the nuclear age, and into the cold war, the US military found high value in having submarines that carried nuclear missiles and were able to stay submerged for extended periods. The challenge was how to communicate with underwater craft around the globe. Radio waves don’t curve around the planet well (or at all), and they don’t carry long distances under water. Scientists discovered that extremely low frequency, or ELF, radio waves might be able to accomplish this feat.

In 1968 the US military set up an experimental ELF antenna array outside of Clam Lake, Wisconsin, to test the transmissibility and the potential negative impacts of ELF broadcasting. Eventually, the transmission site was put into full use, and in the late ‘80s and early ‘90s successfully transmitted brief radio messages to submarines around the world, including one submerged under polar ice above the arctic circle.

To send a signal that strong, you need a large transmitter. The initial Clam Lake ELF site utilized 28 miles of buried transmitter cable. To become the fully operable system, the final ELF array was comprised of two, 2” cables running along a series of power poles. These cable systems extended in two 14-mile-long strings that intersected at the transmission site. In other words, the antenna used about sixty miles of two-inch diameter cable across 28 surface miles of the Chequamegon-Nicolet National Forest. At each end, the cable had to be buried and grounded hundreds of feet deep into bedrock to allow the circuit to complete.

So how does this have anything to do with wildlife? About the same time that the ELF site going into full operation, elk were being reintroduced into Wisconsin. Clam Lake was selected as the destination for these elk, and the ELF antenna array was part of the reason. Those linear miles of clearings were considered ideal habitat for early successional wildlife, including the elk, and would be maintained in an open condition to ensure proper operation of the transmission array.

The ELF array broadcast its signal around the clock nonstop from 1989 until it was decommissioned in 2003 when it became technologically obsolete. Since that time, most of the posts have been removed or cut to a low level.  The buildings were removed except for one that was kept by the Forest Service. The Chequamegon Nicolet National Forest continues to maintain about half of the original open configuration in openings for elk and other wildlife use by mowing and brushing. In areas where it is possible, prescribed burning is also utilized. Since the Wisconsin elk herd is still actively managed, the Forest Service expects they likely will increase the miles that are not in swamplands or so rocky that mowing or brushing by mechanical means is not feasible. This will ensure that the site will continue to benefit Wisconsin’s wildlife for years to come.

The history of the ELF transmitter is fascinating, and can be easily found online. If you want more information, there is a great article by Daniel Olson housed in Military History of the Upper Great Lakes, a collection of Michigan Tech student projects available on the web. The US Forest Service has wildlife staff that would be happy to share more information about the benefits of managing the area long term for elk and other wildlife habitat.