BRIDGEPORT, Calif. (Sept. 21, 2017) -- Deep within the mountains of the Sierra Nevada, Dr. Dan Breton of the U.S. Army Cold Regions Research and Engineering Laboratory recently found himself navigating rough terrain with a squad of Marines, while maintaining communications as part of an information exchange between Marine Corps’ mountain communications training and Army basic research efforts in radio frequency transmission.
Communications within the mountains are difficult for a simple reason – mountains block radio waves. The traditional solution is to use lower frequencies, which allow communications within mountainous terrain, but typically involves the use of large, heavy radios and long, field-fabricated wire antennae to work effectively.
Other than the ionosphere layers of the earth’s atmosphere, the only other reflectors available in mountainous terrain are, of course, the mountains themselves. Breton’s research focuses on measuring and modeling the radio reflectivity of those mountains to better understand how and where reflections from nearby mountains can be used to establish radio links.
“The Mountain Warfare Training Center is situated between the very dry sagebrush hills to the east, and the wetter and taller Sierra, Nevada, mountain range to the west,” said Breton, “providing a completely different environment, and much larger scale from our previous radio frequency channel sounding work done in the White Mountains of New Hampshire.”
The Mountain Communications course teaches high frequency and very high frequency communications techniques applicable to the “compartmentalized terrain” created within the Sierra Nevada Mountains where the course is held. The course is broken out into segments -- classroom time, practical applications and a four and a half day field expedition deep within the mountains above the MWTC. During the field expedition, both Breton and the students had first-hand observations of HF communications working, and VHF communications failing miserably, in mountainous terrain.
“The magic of radio can quickly lose its potency when the link you’re depending on fails, and you don’t know why. The channel sounding data I’ve collected in the area suggests that VHF and ultra-high frequency systems should work better than they did out here, and if you can help those systems work better, then the sizes and weights of radios, antennas, batteries, they all come down compared to HF systems,” said Breton. “The practical challenge is how to become aware of and best exploit topographic reflectors that already exist in the mountainous environment with the equipment at hand.”
While observing the MWTC’s Mountain Communications course, Breton was also able to conduct testing of his own while sharing findings from his previous work with the course participants.
“We successfully collected two full days of channel sounding data, collected on the largest scale to date with our system, with some limitations, but were able to sound the mountain channel from more than 100 different locations,” he said.
“Our preliminary analysis supports the same hypothesis that we built from studying New Hampshire soils, that soil at higher elevation has more moisture and is more reflective,” he said. “In California, this effect is even more pronounced than in New Hampshire due to the low rainfall. The vast majority of our study area was incredibly dry, with mountain form and position weather effects and still-melting snowpack being the major moisture contributors.”
Breton’s research trip was successful in three areas. The data he collected supports his hypothesis, he was able to exchange information on his research and he became an honorary graduate of the Mountain Communications course. The work with the Marines and their instructors provided valuable experience and assisted him in understanding their communications needs now and in the future.