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Figure 3-4. Modulator/Demodulator A1A1 Performance Test (sheet 4 of 4)
Up
TM-11-5820-919-40-2 Radio Set AN/PRC-104(A) (NSN
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Table 3-1. Selected Resistors for Mod/Demod R13, R14 & R15


TM 11-5820-919-40-2
MODULATOR/ DEMODULATOR A1A1 ALIGNMENT
The alignment procedure is to be used an either of these situations: (1) the
performance test calls a potentiometer out of adjustment, or (2) one of the
following is replaced:
1. First Converter, A1A1A1
2. Second Converter, A1A1A2
3. Third Converter, A1A1A3
4. Audio Control Hybrid, A1A1A4
The procedure consists of a preliminary setup and an adjustment procedure.
PRELIMINARY SETUP
TRANSMIT OUTPUT LEVEL ALIGNMENT,
ALC RELEASE TIME ALIGMENT, R29
RECEIVE LEVEL ALIGMENT, R12
DATA MODE AUDIO OUTPUT ALIGMENT, R9
R1, R8, R10, R11
1. Remove the modulator/demodulator
from the receiver/exciter and connect the
1. Turn ALC offset adjust potentiometer
1. Monitor A1J3 via the coaxial atten-
1. Set MODE to V-RCV.
1. Set MODE to D-RCV.
module as in figure 3-3.
R8 to maximum ccw.
uator with the oscilloscope in storage
mode.
2. Connect the rf signal generator to
2. Increase the rf signal generator to
2. Connect the power meter to the
2. Close the PTT switch.
The coaxial attenuator.
-72 dbm (-92 dbm at radio.).
coaxial attenuator.  Set the do power
2. Turn off radio set. Connect a 2K
supply (7 amp) to +26.5v.  Set the step
3. Adjust R11 until power meter reads
resistor in series with the positive out-
3. Adjust the rf signal generator to
3. Adjust data level adjust R9 to
attenuator to 60 db.
28 dbm. Verify test point 13 reads 80
put of the HP-6215A power supply and a
16.0010 MHz and -83 dbm (-103 dbm at
obtain 0.775 0.05 vrms (measure with
10 mv ac.
Sharp steel tip injection probe, apply to
radio).
DVM on ac volts).
3. Connect the fabricated audio input/
J-11, measure the voltage at this point
keying adapter to one of the radio audio
4. Adjust the transmit 50 ohm fixed pad
with the DVM and adjust the HP-6215A power
4. Short gate of Q3 of A1A1A2 (FET case
input plugs.  Connect the audio oscillator
R13, R14 and R15 as necessary in order
supply for + 6VDC at J1-11. Remove probe
is the gate) to ground with a jumper wire.
to the step attenuator.  Monitor the out-
meet the requirements of step 3.
And turn on the radio set. Inject +6V to
put of the step attenuator with the DVM
P-1-11, close CW key.
5. Adjust receive audio level adjust
shunted with 150 ohms and adjust the level
5. Open the PTT switch.
R12 to obtain -2.0 0.1 vdc at TP18.
of the audio oscillator for 0.6 mv rms.
3. Momentarily remove the -6v at pin 11
(Measure with DVM and probe.) Remove
This simulates the input impedance of the
6. Close the CW KEY switch on the audio
and observe the period required for the rf
jumper wire.
LOW VOLTAGE ALARM ALIGMENT, R3
radio, which is 150 ohms in the voice mode
input/keying adapter.
Power at A1J3 to return to 90 percent of
(since the DVM is 1M ohms).  Connect the
full value. This is the LAC release time.
1. Disconnect the rf signal generator
step attenuator to the audio input/keying
7. Adjust 1-kHz tone level R1 to obtain
from the coaxial attenuator and connect
adapter.
28 0.5 dbm at the watt meter (minus 20 db
4. Adjust R29 for an ALC release time
the watt meter. Connect the handset in
for the attenuator.
Of 750 100 milliseconds.
Place of the vtvm.
4. Connect the vtvm to the audio output
with 500 ohms termination.
8. Adjust ALC offset, R8, to obtain a
5. Open CW KEY switch on the audio
2. Close the PTT switch on the audio
0.25-db reduction at the watt meter.
Input/keying adapter.
Input/keying adapter.
5. Set the radio controls located on
the control panel as follows:
9. Adjust sidetone level adjust R10 to
3. Reduce the input voltage to the
obtain 500 10 mv rms at the vtvm.
Radio to +19.0 vdc.
a. ANT SEL to 50 OBMS (bypass)
b. FREQUENCY KBZ to 16,000.0
4. Adjust low voltage threshold adjust,
c. MODE to V-TR
R3, to the point where a continuous
d. VOLUME to MAXIMUM
clicking sound is heard in the handset.
e. SB to USB
2. Close the PTT switch.
DISCONNECT THE TEST EQUIPMENT
23


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