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TM 11-4920-296-14&P
then fed back into the rf microstrip module,
to the transponder.  During the reply inter-
val, the rf signals from the transponder are
which directs them to mixer circuits within
fed first to the rf module circuits, which
the module. Simultaneously with reception
detect (demodulate) them and produce the
of reply pulses, the local oscillator output
corresponding video signals that are then
occurs from the local al oscillator-transmitter
processed in the digital circuits. Secondary
module; this LO signal is directed through
functions of the rf module include checking
the rf microstrip module circuits to the LO
the frequency and power of the rf reply
input of its mixer.  Resulting 30-MHz if.
pulses, steering output interrogation pulses
pulses from the mixer are then directed by
during testing of diversity type transponders,
the rf microstrip module circuits to the if.
video module circuits.
and checking that reply pulses are received
from the correct transponder output. Cir-
2-49.  During testing of diversity type
cuits of the rf module also control the rela-
tive amplitude of side-lobe pulses, with
transponders, the test set varies the ampli-
respect to other interrogation pulses.
tudes of the rf signals transmitted from the
NORMAL and DIVERSITY jacks, so that the
2-47.  The three subassemblies of the rf
strongest signal is alternately transmitted
r e t i e are: the local oscillator-transmitter
from the NORMAL and then the DIVERSITY
jack.  The actual steering signals for this
module the rf microstrip module; and the
alternating strongest signal are fed to the
if. video module. The local oscillator-
t r a n s m i t t e r retie contains two electrically-
rf microstrip module from the if, video
module, If operating correctly, the trans-
identical crystal-controlled oscillator
stages, which are gated to produce the out-
ponder will feed its reply pulses back into
put interrogation pulses (transmitter) and
the jack (NORMAL or DIVERSITY) that
transmitted the strongest signal interroga-
the local oscillator (LO) signal for the
tion. The rf microstrip module processes
r e c e i v e circuits (local oscillator). Both
the reply pulses in the same manner as for
oscillator circuits use crystals whose fun-
single-channel replies, and feeds the result-
damental frequency is 1/6 that of their out-
ing 30-MHz if. pulses to the if. video mod-
put frequency, and both produce outputs
ule.  By use of the steering signals, and
greater than +4 dBm. The transmitter oscil-
detected rf sample signals from the rf
lator, gated by the interrogation input from
microstrip module, the if. video module
the digital circuits, produces output rf
logic circuits confirm that each transponder
pulses at 1030 MHz. During receive (reply)
reply is received via the correct jack
times, the local oscillator is gated by the
(NORMAL or DIVERSITY). By alternately
VIDEO GATE input from the digital section,
transmitting the strongest signal between
to produce the required 1060-MHz LO signal
the NORMAL and DIVERSITY jacks, the test
to the receive mixer circuits. The rf outputs
set checks the transponder ability to reply
from both oscillators are coupled to the rf
from either of its diversity outputs, in cor-
microstrip module circuits via coaxial
rect accord with the strongest signal
reception, If correct diversity reply action
2-48.  The rf microstrip module serves to
occurs, the if. video module feeds a signal
to the digital circuits, which allows the
transfer signals between itself and the other
ACCEPT indication (providing all other
assemblies of the rf module Al, and also for
parameters of the reply signal are correct).
trasferring signals to and from the trans-
ponder under test.  During single-charnel
2-50. In addition to the mixer and steering
transponder testing, the coded rf interroga-
circuits, the rf microstrip module contains
tion pulses (from the local oscillator-
attenuator circuits which control the trans-
transmitter module) are applied through the
mit (interrogation) pulse amplitudes, re-
rf microstrip module to the RADIATED
ceiver sensitivity, and side lobe pulse
TEST ANTENNA connector. From that
point, the interrogation pulses are radiated
2-51.  The if. video module accepts the
(via the antenna) to the transponder. Reply
30-MHz if. pulses from the rf microstrip
pulses received from the transponder are

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