Friday, March 22, 2013

APRS Underground

Map of underground APRS network set up by WB4APR
at Mammoth Cave, Kentucky.
(From website)
Some of the radio gear used in the underground
APRS experiment. (From website)
Automatic Packet Reporting System (APRS) developer Bob Bruninga, WB4APR, has successfully set up an underground communica- tion network in Kentucky's Mammoth Cave, the world's longest known cave system. The ARRL Letter reports that Bruninga, a senior research engineer at the U.S. Naval Academy, set up the system as an experiment in extending the range of underground communications. Normal VHF and UHF radios must be in line of sight of each other and generally have a range of no more than a few hundred feet, according to Bruninga. But by setting up APRS transceivers as packet digipeaters, his team was able to set up a network covering nearly a mile. He also discovered that UHF worked better than VHF, making it possible for cavers without amateur licenses to set up similar links using inexpensive and license-free Family Radio Service equipment.