Receiver Adjustments - Icom IC-78 Service Manualvice Man

5-4 RECEIVER ADJUSTMENTS

Receiver total gain adjustment must perform after transmitter total gain adjustment.
ADJUSTMENT ADJUSTMENT CONDITION
RECEIVER 1 • R2701 (MAIN unit): Center
TOTAL GAIN • Turn R1614 (MAIN unit) to 90
counter clockwise from center posi-
tion.
• Display frequency: 14.10000 MHz
• Mode
• [RIT]
• [NB]
• [P.AMP]
• [ATT]
• Connect a standard signal genera-
tor to [ANT] connector and set as:
Frequency : 14.10150 MHz
Level
Modulation : OFF
• Receiving
2
• [P.AMP]
• [ATT]
• Set an SSG as:
Level
• Receiving
NOISE 1
• Display frequency: 14.10000 MHz
BLANKER
• Mode
• [P.AMP]
• [NB]
• Connect an SSG to [ANT] connec-
tor and set as:
Frequency : 14.10150 MHz
Level
Modulation : OFF
and apply following signal to [ANT]
connector.
100 msec.
• Receiving
2
• [NB]
• Receiving
*This output level of a standard signal generator (SSG) is indicated as SSG's open circuit.
UNIT
Rear
˚ panel
: USB
: OFF (Center)
: OFF
: ON
: OFF
: 1.0 µV* (–107 dBm)
: OFF
: OFF
: 1.0 mV* (–47 dBm)
and OFF
MAIN
: USB
: ON
: OFF
: 3.2 µV* (–97 dBm)
1 msec.
: ON
MEASUREMENT
LOCATION
Connect an AC milli- Maximum audio output
volt meter to [EXT level
SP] connector with
an 8 Ω load.
30 dB of AF level differ-
ence
Connect an oscillo- Maximum noise wave-
scope to check point form
CP1501.
The noise must be
blanked
5 - 8
ADJUSTMENT
POINT
VALUE
UNIT ADJUST
MAIN Adjust in
sequence
MAIN
MAIN
L1103,
L1201,
L1202,
L1621
several
times.
R1614
L1501,
L1502
Verify