Radar System Engineering

SEC. 66] PLANE DISPLAYS INVOLVING ELEVATION 173
the display is expanded in the vertical dimension, so that the height
interval to be covered occupies approximately the same distance on the
tube face. Lines of constant height arehorizontal and equally spaced.
Arrangements are sometimes made to move the range origin off the tube
face to allow expansion of a region of interest.
If the height-finding antenna is required to scan over an appreciable
range of azimuth angles, the RHI is usually
blanked except during a relatively
narrow azimuth sector, in order to improve
10,OOO
the ratio of signal to noise and to avoid Z P
confusion between targets at different ;
azimuths. This sector can be chosen by ,=
adjustment of a calibrated control. c
The RHI is always used in conjunc- ~
tion with a PPI or other display of the ~
horizontal plane; usually this auxlhary G~~~”d~
indicator obtains its data from another Slant range in miles
radar set. The signals from a given tar- F,G. 6.10.—E-scoPe. Lines of
equalheightareshown dotted.
get are correlated in the two displays on
the basis of range and azimuth position. In some cases the height-finding
antenna search] ights in azimuth and is manually aimed in the proper
direction. If it scans in azimuth, the center of the sector which is shown
on the RHI is indicated by a mechanical cursor on the PPI of the search
set.
The E-scope.—The E-scope is a rectangular display in which range
is the x-coordinate and elevation
+20
angle the y-coordinate. Lines of
constant height are hyperbolas
(Fig. 6.10). As in the case of the
B-scope, a delayed range sweep is
often used to allow range expansion.
The elevation analogue of
.s ()
c
0
“%-10
~
El
-20
Ground the micro-B (Sec. 6.5) has found no
echoes application, since the distortion of
-60 -30 0 +30 +60 the E-scope is not particularly
Arimuth in degrees
FIG. 6.11.—C-scope.
harmful and, by allowing it to occur,
the dispersion in the elevation coordinate
can be normalized to make the most e%ective use of the tube face.
In some older sets, the E-scope is used for height indication, but its distortion
and its poor height dispersion at large ranges make it inferior to
the RHI for this purpose.
The C-scope.—The type C display presents the azimuth and elevation
angle coordinates of the scanner as rectangular coordinates on the tube