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TM 11-5820-549-50-1
The transistor for the limiter is contained in the detector
Z2- 4 is developed across a capacitively coupled
integrated circuit Z5. The 455 kHz i.f. signal is applied
double-tuned circuit consisting of C18, T5, C19, C20
to the limiter input at Z5-3 by the capacitor C29. The
and T6.  The signal is then transferred at a reduced
output of the limiter from Z5-1 passing through the
impedance from the tap on T6 by means of C21 to the
isolation resistor R2 drives the discriminator input tuned
input of the second mixer at Z25.  Capacitor C22
circuit, C30 and T7, by means of a top on T7.  The
functions as the signal bypass for the amplifier.
secondary winding of T7 acts as a tickler for the
discriminator  secondary  T8.
The  discriminator
1-9. Second Oscillator
secondary tuning capacitors, detection diodes and a
low-pass filter are contained in electronic component
The transistor for the second oscillator is contained in
assembly Z3.  The low-pass filter has two isolated
the .i.f.  integrated circuit Z2.  The second oscillator
outputs, one, Z3-2, applying signal to the squelch control
operating at 10.245 MHz is a Pierce type with the crystal
R5 and the other, Z3-1, applying signal to the volume
Y2 operating at its fundamental parallel resonant mode.
control R7. Capacitor C36 is the signal bypass for the
The leads of crystal (type CR-64U) are soldered to the
limiter. The B+ filter network C22, L6 and C36 provide
circuit board. Capacitors C24 and C25 form the phase-
isolation between the 455 kHz i.f.  amplifier and the
reversing voltage divider for the feedback signal from
collector, Z2-1, to ground and from base, Z2-2 to
ground. Capacitor C23 couples the 10.245 MHz signal
1-13. Audio Circuit
to the input of the second mixer at Z2-5. Capacitor C22
is the signal bypass for the circuit.
The recovered fm modulation (voice or tone) is applied
across the volume control R7. The desired level of the
1-10. Second Mixer and 455 KHz Filter
signal is selected by the adjustment of R7 and is
coupled to the input of the audio amplifier at Z5-13 by
The transistor for the second mixer is contained in the
capacitor C40. The audio amplifier is contained in the
i.f. integrated circuit Z2. Both the 10.7 MHz i.f. signal
detector integrated circuit Z5.  The output signal is
and the 10.245 MHz oscillator signal are coupled to the
applied from Z5-10 to the horn transducer LS1 or the
input of the second mixer Z2-5, at the junction of C21
headset H-302(XE-1)/PRR-9 by means of the earphone
and C23.  The desired difference frequency signal of
jack J5.  Both the horn and the headset have an
455 kHz is developed across the input of the ceramic
impedance of approximately 220 ohms and a resistance
ladder filter FL1.  The filter has a -6 decibel (db)
of 80 ohms. Capacitors C40 and C42 are instrumental
bandwidth of approximately 40 kHz and a -60 db
in determining the low frequency roll-off. Capacitor C43
bandwidth of approximately 70 kHz. Capacitor C22 is
assures stability of the audio amplifier by minimizing
the signal bypass for the second mixer.
gain at frequencies above the audio spectrum.  The
signal bypass for the audio amplifier B + line is capacitor
1-11. I.f. Amplifier, 455 KHz
C36.  Diode CR3, in series with J5, allows the horn
transducer LS1 to function in the event J5 short circuits
Three cascaded stages of 455 kHz gain are contained in
to ground (B-).
the i.f. integrated circuit Z2. The input signal for the
first stage is taken from the output of the ladder filter
1-14. Tone Squelch Circuit
FL1 and is introduced at Z1-8 to the amplifier.
Capacitor C26 provides coupling between the first and
second stages of gain from Z2-9 to Z2-10. Capacitor
a. Tone squelch (150 Hz) is activated when the
C28 couples the signal from the second to the third
receiver control is initially turned on. Squelch switch S1,
stage of gain from Z2-11 to Z2-12.  Capacitor C29
which is a part of the receiver control, is open in this
couples the signal from the output of the third stage at
condition. The audio amplifier is disabled and dissipates
Z2-13 to the input of the limiter at Z54.  The signal
no power in the absence of signal. Upon reception of a
bypass for the B + line is C22.
signal with 250 Hz sidetone modulation, the 150 Hz
signal is applied across the squelch adjust potentiometer
1-12. Limiter and Discriminator
R5. The proper level of signal is coupled from R5 by
capacitor C35 through R3 to the input of the squelch
circuit at Z5-4. The. transistor for

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