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TM 11-5825-271-34
nects the external battery to the unregulated supply line
is reduced to zero when the TONE switch S3 is switched
through isolation diode CR10.
off. When the voltage at the cathodes of CR28 is zero
e. AC Remote Monitor. A secondary winding of T1l
(S3 off), the oscillator ceases to produce an output
Transistor Q9 Is an emitter follower, providing a low
on the transformer chassis provides 20 Vac across P1-1
impedance tone output to the keyer gate Q10
and P1-2 (fig. FO-3). The output between P1-1 and P1-
f.  Keyer Gate. Field-effect transistor Q10 provides
3 can be used for monitoring at a remote site.  This
transient-free gating of the 1020 Hz tone signal from Q9
output can be adjusted by R4 from 0.5 to 5.0 Vac, when
When the keyer control signal at the gate of Q10 is high,
terminated by a 600 ohm load.
Q10 is off and the tone is not fed to Q11. When the
keyer control signal is low, Q10 is switched on and the
2-15. Exciter Assembly A1A2
tone signal is connected to amplifier Q11. The keyed
tone signal from Q11, routed through R67 and C30, is
a. 12Vregulator. The +24 Vdc at P1-14 is scaled
used as the modulation signal for the mark/space
down to +12V by R13/R14. Transistor Q1 is a voltage
follower, providing a low Impedance + 12V supply for
g. Voice Compressor. The external voice input at
circuitry within the exciter assembly A1A2.
P1-17 is applied to the base of Q22 through R72 and
b. RF Oscillator. The switched 24 Vdc for the rf
C35 Field-effect transistor Q20 acts as a variable
oscillator is received at P1-5 from contacts 4-7 of
resistor, controlled by the feedback from Q37 of the low
shutdown relay K1 (fig. FO-1). When 24 Vdc supply at
pass filter. If the signal at output of the low pass filter,
P1-5 is present (normal operation), the rf oscillator circuit
exceeds the dc bias at the base of Q21 (set by
operates at 10 times the carrier frequency. Crystal Y1,
COMPRESSION  LEVEL  potentiometer  R13),  Q23
operated at series resonance, introduces positive
conducts and reduces the bias at the gate of Q20 This
feedback from the collector of Q3 to the base of Q2.
reduces the drain-source resistance of Q20 and
The signal level at the emitter of Q3, approximately 12V
therefore the signal level applied to Q22 At the same
p-p, is applied to the frequency divider U9 Note that in
time,  Q23  switches  on  Q19  which  lights  the
the event of  a  malfunction,  shutdown  relay K1
COMPRESSION LIMIT lamp connected to P1-16 Diode
deenergizes, and the 24 Vdc at P1-5 is switched off.
CR34 and resistor R77 provide a fast attack/slow decay
Thus, the rf oscillator ceases to operate and the NDB
characteristic to the compressor circuit
transmitter is effectively turned off.
h. Voice Amplifier. Transistor Q22 provides high
c.  Frequency Divider. Integrated circuit U9 divides
gain amplification of the voice signal The output from
the rf output from the oscillator circuit by 10 to produce
Q22 is buffered by emitter follower Q24 and applied to
the transmitter carrier frequency. The output at U9-12,
the high pass filter circuit
12V p-p, is buffered by Q4. Transistors Q5 and Q6 form
i.  Voice Filter. The voice filter consists of a high
a complementary output stage which produces a square
pass filter formed by Q25 through Q30 and a low pass
wave output at the carrier frequency.
filter comprising Q31 through Q37 Together they form a
d. RF Filter and Detector The square wave carrier
six-pole, Chebyshev filter which is flat to within 3 dB from
signal from Q5/Q6 is passed through a low-pass filter to
300 to 3000 Hz, falling off sharply below and above these
remove unwanted harmonics.  The filter covers the
frequencies. The output from the voice filter is buffered
frequency band of 320 to 535 kHz when links 3 and 4 are
by Q37 and fed to the mark/space modulator through
removed, or a frequency band of 190 to 320 kHz when
R113 and C52.
links 3 and 4 are in place. Transformer T1 converts the
j.  Sawtooth Oscillator. Transistors Q12, Q13, and
output impedance of the filter to 50 ohms for proper
Q14 form a sawtooth oscillator operating at a frequency
matching with the pa module A1A4. Diode CR24 and
of approximately 65 kHz The output at the emitter of Q14
capacitor C14 form a peak detector and its output at P1-
is a linear ramp, rising from 3 4V to 10 4V.
7 is routed to TEST switch S2 and TEST meter M1 (fig.
k.  Mark/Space Modulator.  Transistors Q15 and
FO-2) to provide an indication of the drive level.
Q16 form an emitter-coupled slicer circuit The sawtooth
e. Tone Oscillator.  Transistors Q7, Q8; and Q9
signal from Q14 is applied, through L4, to the base of
and associated components form a phase-shift oscillator
Q15. The potential at the base of Q16 is proportional to
operating at 1020 Hz The symmetrical clipping of the
the instantaneous audio level and the preset carrier level.
feedback signal by CR27 and CR28, and the variable dc
When the base of Q16 is at a constant potential, a 1 4V
bias at the cathode of CR28, allows adjustment of the
square wave signal with a constant pulse width is
output level (tone modulation depth) from the tone
developed at the collector of Q15 However, if the
The dc bias at the cathode of CR28,
potential at the base of Q16 rises, the conduction period
developed by R115 and ONE LEVEL potentiometer R12,

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