[This message is from AA1BU. Please don't reply to me. - AD1C]
To: <topband@contesting.com>
Msg #176 From: AA1BU Date: 30-Mar 0643Z Subj: ROTHR text
If you've heard the staccato burts on 160M, this may be of interest.
Relocatable over-the-horizon radar (ROTHR) originally developed for
the U.S. Navy to provide wide area ocean surveilance for fleet defense
is now being used for deterring the flood of small planes and boats
carrying millions of dollars worth of illegal substances.
The first ROTHR system was operational from Amchitka, one of the
Aleutian Islands located 1300 Km off the Alaskan coast. The
Department of Defense is operating ROTHR facilities from a test site
in Virginia to search for drug traffic in the Carribean along with a
second site in Texas. Together these systems monitor 8.5 million
square kilometers of air and sea space from Mexico to Columbia to the
islands of Trinidad and Tobago.
ROTHR is a bistatic radar (it has separate receive and transmit
sites). Unlike conventional radars (300 MHz - 30 GHz) which are line-
of-site sensors ie, they require a direct path between the radar
antenna and the target, ROTHR operates in the HF (2 - 30 MHz) band
bouncing signals off the ionosphere back down to the target where they
are backscattered to the radar antenna. This allows ROTHR to detect
targets well beyond the horizon, making it difficult for targets to
mask themselves by flying low or behind land masses.
ROTHR's transmit site generates high power waveforms used by the
backscatter radar and the vertical and downrange sounders.
Phased-array antennas electrically steer the transmitted signal
downrange while the vertical sounder antennas direct its energy
straight up to the ionosphere. Because of the long transmitted
wavelengths, the antennas stand 60 meters high. The array comprises
372 dipole pairs about 2.5 Km in length.
ROTHR's environmental monitoring capabilities provides continuous
information about which frequencies are in use by other systems, such
as the Coast Guard or ham radio operators. This monitoring determines
the radar operating parameters for optimum target detection.
Therefore, two radars are needed: one to search for targets and one to
monitor the ionospheric environment.
ROTHR was developed by Raytheon Co.with support from NRL, NRaD and
Rome Laboratories. An in-depth article can be found in the Microwave
Journal, March 1998. The Dale Brown novel "HAMMERHEADS"(Putnam
Berkley Publishing Group) is an accurate techno-thriller based on
ROTHR technology as the ultimate high tech weaponry in the war against
drugs.
73, Joe at KB1H
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