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(4) The pulse train must exist with not less than
the minimum pulse train persistence.
The CRT display is divided into eight sectors. Strobes
are displayed only in those sectors in which signals
meeting all threat criteria are present. This reduces
display clutter by eliminating low-level and wide pulse
width signals and by selective sector display. Intercepts
which meet these requirements are displayed as described
in paragraph 4.37.3 a.
NOTE
In this mode, uncorrelated low band signals
will not give any indications.
A typical display when operating in the discriminator
ON mode is shown in figure 4-22. Conditions are the
same as for figure 4-21, but it is assumed that one or
more threats have been identified in the 225 to 270 degree
sector.
4-73
TM 1-1520-238-10
Figure 4-22. Radar Warning Discriminator On
Mode Display
4.37.4 AN/APR-39(V)1 Self-Test Operation. The selftest
checks all RW set circuits except antennas, highpass
filters and detectors in the high band receiver,
bandpass filter and detector in the low-band receiver,
analysis signal commutator, and high and low-band
blanking circuits. The self-test procedure is done before
operation and when any malfunction is detected. A selftest
display is shown in figure 4-23.
a. Self-test procedures are as follows:
1.
2.
3.
PWR switch - ON. Panel lights illuminate.
DSCRM switch - OFF. Wait l-minute for
warmup. Monitor display CRT and audio.
SELF-TEST button - Press and hold.
a.
b.
c.
FWD and AFT strobes appear, extending
to about the third circle on the display
graticule, and a 2.5 kHz (approximately)
PRF audio is present immediately.
Within about 6 seconds, alarm audio is
present and the MA light starts flashing.
Display BRIL control - Turn cw and CCW.
Strobes brighten (cw) and dim (ccw) as
control is turned. Set BRIL control for desired
brightness level.
Figure 4-23. Radar Warning Self-Test Mode
Display
d. AUDIO control - Turn between max ccw
and max CW. Audio will not be audible at
max ccw and clearly audible at max CW.
e. SELF-TEST pushbutton - Release. All
indications cease.
4. DSCRM switch - ON.
5. SELF-TEST button - Press and hold.
a. Within about 4 seconds a FWD or AFT
strobe (either may appear first) and a 1.2
kHz (approximately) PRF audio will be
present.
NOTE
Occasionally, during the period between
pressing SELF-TEST and appearance of
the first strobe, a distorted dot on the display
and intermittent audio will be present.
This is not a fault isolation.
b. Within about 6 seconds, the other strobe
will appear and the PRF audio frequency
will double.
c. Several seconds later alarm audio will be
present and the MA light starts flashing.
d. SELF-TEST button - Release. All indications
cease.
6. PWR switch -As desired.
4-74
TM 1-1520-238-10
4.38 RADAR WARNING SYSTEM AN/APR-39A(V)1.
The radar warning (RW) system provides visual and
aural warnings of radar reception. This is done by receiving,
processing, and displaying potential threats in
the radio frequency (RF) environment. Potential
threats are displayed as symbols on the RW display and
announced over the intercommunication system. The
emitters that it displays are derived from the emitter
identification data (EID) contained in the user data
module (UDM) that is inserted in the top of the digital
processor. The UDM contains the electronic warfare
threat data that goes to make up the specific library for
a specific mission or geographical location. When a
match of the electronic warfare data occurs the processor
generates the appropriate threat symbology and
synthetic audio. The operating controls and indicators
of the RW control panel (fig 4-20) are described in table
4-25. When installed, the AN/AVR-2A(V)1 laser detecting
set provides early warning against laser threats. In
the event of simultaneous warnings, one from the radar
warning and one from the laser detecting set, the laser
warning signals have priority. Refer to paragraph 4.39.
Table 4-25. AN/APR-39A(V)1 Radar Warning System Control/Indicator Functions
Control/
Indicator
PWR
Position Function
ON Turns set on. Listen for synthetic voice message - APR 39 POWER UP Plus (+)
sign will appear and stabilize in center of CRT.
TEST
OFF Turns set off.
When momentarily depressed initiates self-test confidence check except for
antennas and antenna receiver cabling.
MODE 1 Selects normal voice message format.
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