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13. Tone Generator Module A23
sure maximum output with minimum dis-
tortion. A portion of the tone oscillator
output signal, from the junction of collector
The tone oscillator functions only during
resistor R11 and potentiometer R12, is fed
transmission. The 150-cps output tone is
back through resistor R5 to the base of
applied to the speech amplifier limiter
transistor Q1 to stabilize the oscillator
module (para 12) which frequency-modu-
gain and prevent distortion due to exces-
lates the transmitter output carrier signal
sive base drive. The 150-cycle tone output
with the tone at all times during transmis-
is applied to speech amplifier A22 (para
sion. The 150-cps tone disables the squelch
12) in the transmitter section and to tone
circuit in the distant receiver.
squelch amplifier A24 (para 11) in the re-
a. During transmission, +10-volt dc op-
ceiver section.
erating voltage is applied to transistor Q1
c. The combination of resistors R6, R7,
which oscillates at 150-cps. The frequency
R5, and RT2 and potentiometer R12 pro-
is determined by the resistance-capaci-
vides base-to-emitter fixed bias for oscil-
tance (rc) phase-shifting network consist-
lator Q1. Resistor R8 is the emitter
ing of capacitors Cl, C2, and C3 and re-
swamping resistor for oscillator Q1; R9
sistors R1, R2, and R4. Slight adjustment
is the swamping resistor for Q2. Resistor
of the frequency can be made by adjust-
R9 is the emitter swamping resistor for
ment of FREQ ADJ potentiometer R3. Os-
Q2. Potentiometer R12 is the output level
cillation is sustained by a feeding back of
adjustment for the 150-cps tone output.
the collector output through phase-shifting
The 150-cps tone output from R12 can be
capacitors C1, C2, and C3, to the base of
measured at test jack J3.
Q1. Each capacitor shifts the signal 60 to
provide the regenerative 180 phase shift,
14. Sidestep Oscillator Module A20 ond
Temperature compensation is achieved by
Quarter-Wave Network Module A19
thermistor RT2, which provides a temper-
ature compensated bias on the base of Q1,
The sidestep oscillator (fig. 8) is a mod-
and thermistor RT1, which compensates
ified Hartley type. A quarter-wave network
the phase-shift network.
(fig. 9) is connected to the oscillator tuned
b. The feedback amplifier is used to in-
circuit to stabilize the frequency. The
Figure 7. Tone generator module A23, schematic diagram.

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