Radar System Engineering

SEC.6.14] PRECISION TRACKING OF A SINGLE TARGET 205
At the operating frequency of 205 Me/see, a 4 by 4 array of dipoles with
reflectors gives a beam about 2-1° wide in azimuth and in elevation.
Return echoes are received on two separate antenna arrays, each with its
ownreceiver, Onearray, sixdlpoles ~videby four Mgh, @vesinformation
to an azimuth scope; the other, two dipoles wide and six high, provides
signals to an elevation scope. The receiving arrays have two separate
feeds arranged to produce different phase relations between the elements
of the array. Thus, byswitching theazimuth receiver from one feed to
another, the beam pattern of the receiving antenna can be switched from
one to the other of two overlapping lobes equally displaced in azimuth on
opposite sides of the normal to the antenna array. Similar switching
arrangements are provided for the elevation antenna and its receiving
channel.
The antennas are mounted on a single cross arm, which rotates in
azimuth with a central pedestal enclosing the radar circuits and can be
turned about its own axis to elevate the arrays. Three operators, each
with a scope, ride with the cross arm as it turns. A range operator is
provided with an A-scope having a movable marker which he keeps on
the signal being tracked. His rotation of the range handwheel feeds
range information to a “height converter,” a computing mechanism
employing a three-dimensional cam to combine slant range and elevation
angle in such a way that continuous target altitude information is produced.
Rotation of the range handwheel also brings the signal being
tracked into the center of the azimuth and elevation display tubes.
Each of these tubes is manned by an operator provided with a handwheel
which moves the antenna in the appropriate angular coordinate. The
display is type K (Fig. 6“4). It is the duty of the azimuth operator to
keep the two signal ‘‘ pips” in the center of his scope matched in height
by turning his handwheel; the elevation operator has a similar task.
The maximum design range of the set is 40,000 yards, and the repetition
rate is 4098 pps. With a power output greater than 50 kw and a
pulse width of 7 to 15 psec, the set is very conservatively designed, and
can track targets much beyond its rated range. Angular accuracies
attainable in practice with this equipment, about + 1°, are too poor to
permit good blind antiaircraft t fire, and because of ground reflections the
equipment suffers from severe errors in reading elevation at angles smaller
than about 10°. However, this versatile, rugged, and readily mobile
equipment was available in quantity early in the war, and served many
useful roles, being used for fire control, short-range search and warning,
and searchlight control.
Conical Scan and Error Indication.—In a situation where not more than
one target at a time is expected in the radar field of view, the equipment
necessary to track a target can be considerably simplified. Such a case