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<br />Presented at American Meteorological
<br />Society 18th Conference on Radar
<br />Meteorology, March 28-31, 1978,
<br />Atlanta, Georgia
<br />
<br />PROJECT SKYWATER SWR-75 RADARS
<br />
<br />William F.. Harrison
<br />
<br />Bureau of Reclamation
<br />Denver, Colorado
<br />
<br />The Bureau of Reclamation's Project Skywater has
<br />developed, under contract with Enterprise
<br />Electronics Corporation, Enterprise, Alabama, a
<br />pair of mobile 5-cm radars. They were designed
<br />to satisfy the basic requirements of several
<br />weather modification research efforts, each
<br />requiring different radar performance character-
<br />istics. One of the projects for which the
<br />radars were designed is the High Plains
<br />Cooperative Program (HIPLEX), which focuses on
<br />warm-season convective clouds and precipitation.
<br />The radars are also used in the Sierra
<br />Cooperative Pilot Project, which concentrates on
<br />winter orographic storms. The radars were
<br />designed primarily for postanalysis capabilities
<br />and, although not flexible enough to satisfy .
<br />every requirement of every research program,
<br />there are numerous optional operating features
<br />that make the system one of the most unique
<br />available.
<br />
<br />The radars are housed in a IZ-meter Dorsey semi-
<br />.' ailer separated into three areas: (1) mainte-
<br />ce, (Z) operations, and (3) antenna. The
<br />intenance area consists of two workbenches,
<br />storage cabinets for spare parts, and storage
<br />space for the electronic test equipment. The
<br />operations area consists of (1) the magnetic
<br />tape storage cabinet, (Z) the master console
<br />containing an A-scope, a PPI scope, and an
<br />RHI-scope plus all of the controls for radar
<br />operation, (3) two magnetic tape recorders,
<br />(4) an Air Traffic Advisory console consisting
<br />of a PPI scope and the IFF control switches,
<br />(S) the Transmitter-Receiver cabinet, and
<br />(6) a rack of built-in electronic test equipment
<br />necessary for radar calibration. The antenna
<br />area consists of (1) dual fire suppression
<br />systems, (Z) the A-frame for holding the
<br />Pedestal/Antenna system independent of the semi-
<br />trailer roof and walls, and (3) heating elements
<br />for maintaining temperatures during the winter
<br />seasons.
<br />
<br />The antenna is a 4,Z7-meter circular horn-fed
<br />paraboloid with greater than 43-dB gain, .hori-
<br />zontally polarized, and a 0.9 x 100 beam width.
<br />The horn is held in the center of the dish by
<br />pinned spars. The antenna pattern was maximized
<br />at the factory and the spars were then pinned.
<br />The antenna pattern was again taken with con-
<br />sistent results. The pinning of the spars
<br />allows dismantling and reconstruction of the
<br />antenna and feed to as near its original position
<br />as mechanically possible, The deviations from
<br />mechanical and electrical zero are determined
<br />using solar methods and are discussed later in
<br />
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<br />
<br />this paper. The antenna has been divided in
<br />two sections for ease of shipment and
<br />reconstruction.
<br />
<br />The antenna is mounted on the 2.6-meter
<br />pedestal, which also has the IFF antenna
<br />suspended on it. The IFF antenna is Z.75
<br />meters long and 0,31 meter wide, and has a
<br />system gain of approximately 18 dB. The beam
<br />width is 70 in azimuth and 500 in elevation. The
<br />two antennae and the pedestal are enclosed by a
<br />41-piece 5.5-meter fiberglass radome that
<br />attaches to the top of the semitrailer.
<br />
<br />During transportation, the radome is removed
<br />and shipped in its containers, the antennae are
<br />removed and shipped, and the pedestal is posi-
<br />tioned to the bottom of the semitrailer so that
<br />no portion protrudes above the top of the
<br />trailer roof. .
<br />
<br />The transmitter portion of the radar is a
<br />tunable coaxial magnetron with operating limits
<br />of 5460-5650 MHz, centered at 5550 MHz, and a
<br />ZSO-kilowatt power output. A Z-microsecond
<br />pulse width recurring at either Z07 or 414
<br />pulses per second is incorporated, and a dual
<br />TR tube duplexer is included. The receiver
<br />portion has both a logarithmic and a linear
<br />section to satisfy different user needs. The
<br />logarithmic receiver has a dynamic range of
<br />80-85 dB, a 0.6-MHz band width, uses a 3D-MHz
<br />intermediate frequency, and is preceded by both
<br />a filter to meet the Office of Telecommunications
<br />Policy for Radars and a 17-dB gain parametric
<br />amplifier. The linear receiver has a Z6-dB
<br />dynamic range; it also is preceded by the filter
<br />and parametric amplifier and has a 0.6-MHz
<br />band width (Smith, 1977).
<br />
<br />The logarithmic receiver output is fed to the
<br />Digital Video Integrator Processor (DVIP), which
<br />averages the returns to output a single value
<br />per range bin. The DVIP has the capability of
<br />averaging Z50 range bins of 1/4, l/Z, 1 or
<br />Z km lengths and taking 16, 3Z, 64, or lZ8
<br />samples across either 0.50 or 10 of azimuth.
<br />The DVIP takes 1/8-km range samples on each PRF,
<br />adding Z, 4, 8, or 16 samples together and then
<br />dividing by Z, 4, 8, or 16 to give a single
<br />1/4-, l/Z-, 1-, or Z-km value per PRF to be
<br />stored in a 16- by Z56-shift register. Succeed-
<br />ing PRF's are taken, and the value of the
<br />associated range bin is shifted in and added to
<br />the previously stored range bin value. When the
<br />17th, 33rd, 65th, or 129th sample is taken, the
<br />previous 16, 3Z, 64, or 128 samples are divided
<br />
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