Radar System Engineering

288 ANTENNAS, SCANNERS, AND STABILIZATION [SEC. 912
of energy which would penetrate straight through would still be focused
in azimuth and so would cause spurious signals. A solid construction is
therefore typical of shaped cylindrical reflectors. Paraboloid reflectors
need not be solid, since the radiation leaking through them from the point
antenna feed is not focused and cannot cause sharply defined false echoes.
The antennas rotate about a \crtical axis at 2 or 4 rpm, together with
their respective transmitters and common modulator. There is no ele-
S_.
7
Linear arrays
H?usings for electronic
uni~
I
FIG.
9.15.—Long.range microwave antenna mount with two 25-ft c3,1indricalreflectors.
vation control of the beam except for initial adjustment at the time of
assembling in the field. No r-f rotary joints are necessary in the waveguide
transmission lines. Slip rings are required around the azimuth
axis in order to carry 60-cps power, control voltages, and video signals.
Although weighing 6 tons, the ground-based version of this mount
can be disassembled and stowed on trucks in 4 hr. The truck-mounted
version is illustrated. The mount has operated in winds up to 80 mph,
and the design is such that 125-mph winds should not cause damage.
The A iV/APS-10.-In spectacular contrast with the foregoing is the
more recent of two alternative scanner designs for the AN/APS-10
navigational radar (Fig. 9.16); it is airborne and weighs about 13 lb.
The antenna is a paraboloid 18 in. in diameter, fed at the 3-cm band by a