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Map of underground APRS network set up by WB4APR
at Mammoth Cave, Kentucky.
(From aprs.org website) |
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Some of the radio gear used in the underground
APRS experiment. (From aprs.org 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.
