absorption to propagation loss is small compared to
refractive effects.
. ECM accounts for the ducting in evaporative
ducts, surface-based ducts, and low-elevated ducts,
provided the victim radar antennas are within the
elevated duct. The program does not, however, properly
account for the over-the-horizon region for
low-elevated ducts when the bottom of the duct is above
the antenna height.
. The victim radar must be surface-based.
. Prior to running this program, a primary
refractivity data set must be selected.
. Output from this program is classified and
labeled corresponding to the classification of the radar
or jammer.
FUNCTIONAL DESCRIPTION
The ECM display program provides a plot of signal
strength relative to the free-space value versus height
for five equally spaced discrete ranges.
Figure 7-1 shows an example output of the ECM
effectiveness display. The ECM output consists of five
range for most effective jamming. Jamming is most
effective where the plotted line is farthest to the right on
each display.
D-VALUES (DVAL)
LEARNING OBJECTIVES: Define the DVAL
program. Recognize program inputs. Identify
applications, limitations, and assumptions.
Explain an example of the D-value profile.
The DVAL program is used to compute profiles of
D-values. A D-value is defined as the difference
between the actual height above mean sea level (MSL)
of a particular isobaric surface and the height of the same
pressure surface in the U.S. Standard Atmosphere.
Program input consists of temperature and geopotential
height profiles with respect to pressure, output altitude
increment, and specification of units for which the
output is desired.
APPLICATION
D-values are used by naval aviators to make
displays. The displays suggest optimum altitude at each
pressure-bomb detonation altitude corrections.
Figure 7-1.-Example output of the ECM effectiveness display.
7-2
