ALIGNMENT

REQUIRED TEST EQUIPMENT

Aligning the MR8100 calls for the following equipment:

PREPARING FOR ALIGNMENT

Before you begin the alignment procedure verify that the MR8100 is connected to a 13.8 Vdc (12.4 – 15.2 Vdc) power supply. Turn the power switch off, set the volume control fully counterclockwise, and set the squelch control fully clockwise.

DISASSEMBLY

Use the following procedure to disassemble the MR8100 for alignment:
  1. Remove the six screws on the bottom of the MR8100.
  2. Turn the MR8100 over, grasp each side of the front panel and pull up on it.
  3. When the front panel clears the chassis, set the front to one side to expose the shield plates.
  4. You can access all the alignment points through the holes in the shield plates.

GENERAL ALIGNMENT PROCEDURE

 Step 
 Preset to 
 Adjustment 
 Remarks 
1
CH: 14 CT702 Phase-Locked Loop (PLL) Adjustment
  1. Connect the frequency counter to TP4 (R8).
  2. Adjust CT702 to 10.400000 MHz ±0.00001 MHz.
2
CH: 15 CT701 Adjust CT701 to 10.399850 MHz ±0.00001 MHz.
3
CH: 14 CT702 Check for a frequency of 10.400000 MHz. If the
tolerance is more than ±10 Hz, readjust CT702.
4
CH: 15 No adjustment Connect the oscilloscope to TP4 and confirm that the
waveform is a sine wave with a peak-to-peak voltage of
550 mV ±100 mV.
5
CH: 9 L701 Voltage-Controlled Oscillator (VCO) Adjustment
  1. Connect the oscilloscope or DC voltmeter to TP2
    (R642).
  2. Adjust L701 to 12.5V ± 0.1V.
6
CH: 4, 5, 6, 7, 8 No adjustment Confirm that the VCO is at the channel voltage listed in
the following table:

 Chan 
#
 Freq. 
(MHz)
 DC Voltage 
(volts)
4
138.1500
2.2 ± 0.5
5
162.4000
8.1 ± 0.5
6
173.2250
10.2 ± 0.5
7
406.8750
5.1 ± 0.5
8
453.2500
8.7 ± 0.5
9
511.9125
12.5 ± 0.1

7
CH: 1 L704 Adjust L704 to 1.2V at TP2.
8
CH: 2, 3 No adjustment Confirm that the VCO is at the channel voltage listed in
the following table:

 Chan 
#
 Freq. 
(MHz)
 DC Voltage 
(volts)
1
30.0500
1.2 ± 0.1
2
40.8400
5.6 ± 0.5
3
49.9000
8.7 ± 0.5

9
CH:   2
SG:   40.84 MHz
    50 mV
L604 IF Adjustment
  1. Connect the signal generator to the ANT terminal
    and the oscilloscope to TP1 (Pin 18 of IC2).
  2. Adjust L604 to the maximum level reading on the
    oscilloscope with the sweep time set to where you
    can observe a waveform.
10
CH:   2
SG:   40.84 MHz
    1 mV
    No modulation
L2 Discriminator Adjustment
  1. Connect the signal generator to the antenna
    terminal
  2. Connect the digital voltmeter to TP3 (R51).
  3. Adjust L2 to 3.5 Vdc ±0.05 Vdc.

RECEIVER ALIGNMENT

To prepare for alignment preset the following:
 Step 
 Preset to 
 Adjustment 
 Remarks 
1
CH:   5
SG:   162.4 MHz
    0.5µV FM
Volume control Adjust the sensitivity as follows:
  1. Connect the wattmeter (or voltmeter) to the audio
    output terminal.
  2. Adjust the volume control to 1000 mW (2V across
    the 4W resistor.)
2
CH:   5
SG:   162.4 MHz
    0.5µV FM
L604
L611
L613
  1. Connect the SINAD meter to the audio output
    terminal.
  2. Adjust L604, L611, and L613 for the best SINAD
    level.
  3. Adjust the signal generator to a 12 dB SINAD level
    and confirm that the signal generator output voltage
    is less than 0.8µV.
3
CH:   2
SG:   40.84 MHz
    0.3µV FM
L607
L612
  1. Adjust L607 and L612 for the best SINAD level.
  2. Adjust the signal generator to a 12 dB SINAD level
    and confirm that the signal generator output voltage
    is less than 0.8µV.
4
CH:   7
SG:   406.875 MHz
    0.6µV FM
CT601
CT602
CT603
  1. Adjust CT601, CT602 and CT603 for the best
    SINAD level.
  2. Adjust the signal generator to a 12 dB SINAD level
    and confirm that the signal generator output voltage
    is less than 0.8µV.
  3. Repeat steps a. and b. several times. After each
    repetition, check for a 12 dB sensitivity of less than
    1.0µV.
5
CH: 8, 9
SG: FM
No adjustment Confirm that the 12 dB SINAD sensitivity is less than
1.0µV for each channel.
6
CH: 10, 11, 12 No adjustment Confirm that the 12 dB SINAD sensitivity is less than
1.6µV for each channel.
7
CH: 5
SG: 162.40 MHz
SINAD: 21 dB
(TYP. 0.7µV) FM
Squelch: Fully
counterclockwise
VR2 Adjust the squelch as follows:
  1. Rotate VR2 fully counterclockwise.
  2. Rotate VR2 clockwise until an audio output voltage
    appears.
8
CH: 5
SG: No signal
VR1 Adjust VR1 for a symmetric noise waveform at R36.

ASSEMBLY

Use the following procedure to assemble the MR8100:
  1. Verify that the rubber seal around the chassis is properly seated.
  2. Carefully turn and replace the front cover on the chassis.
  3. Press the front cover into place.
  4. Turn the MR8100 over.
  5. Replace the six screws on the bottom of the MR8100.


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