Pll And Transmitter Adjustments - Icom IC-A23 Service Manual

5-2 PLL AND TRANSMITTER ADJUSTMENTS

• The "PLL LOCK VOLTAGE" adjustment must be performed at the "NORMAL" mode.
• "REFERENCE FREQUENCY", "IDLING CURRENT", "OUTPUT POWER" AND 'AM MODULATION" adjustments must be per-
formed at the "ADJUSTMENT" mode.
ADJUSTMENT ADJUSTMENT CONDITIONS
PLL LOCK 1 • Operating frequency: 136.975 MHz
VOLTAGE • Receiving
REFERENCE 1 • Operating channel : 0 ch [FREQADJ]
FREQUENCY
• Connect the RF power meter or a 50 Ω
dummy load to the antenna connector.
• Transmitting
IDLING 1 • Operating channel : 1 ch [PWR-1]
CURRENT
• Connect the RF power meter or a 50 Ω
dummy load to the antenna connector.
• Transmitting
OUTPUT 1 • Operating channel : 2 ch [PWRADJ]
POWER
• Transmitting
AM 1 • Operating channel : 2 ch [PWRADJ]
MODULATION
[PWRADJ] • Connect an audio generator to the
[MIC] connector and set as :
• Set a modulation analyzer as :
HPF
LPF
De-emphasis : OFF
Detector
• Transmitting
2 • Connect an audio generator to [MIC]
connector and set as :
1 kHz/20 mV
• Transmitting
• LOGIC UNIT TOP VIEW
R41
AM modulation
adjustment
MEASUREMENT
UNIT
RF
Top
(136.975 MHz) panel
Side
(136.975 MHz) panel
Top
(136.975 MHz) panel
Top
(136.975 MHz) panel
1 kHz/200 mV
: OFF
: OFF
: (P-P)/2
• RF UNIT TOP VIEW
R554
AM modulation
adjustment
L40
PLL lock voltage
adjustment
5 - 3
LOCATION
Connect a digital multi
meter to the check
point CP1.
Loosely couple the fre- 136.9750 MHz
quency counter to the
antenna connector.
Connect a DC amme-
ter between the DC
power supply and
transceiver's DC
power jack.
Connect an RF power
meter to the antenna
connector.
Connect a modulation
analyzer to the anten-
na connector via an
attenuator.
ADJUSTMENT
VALUE
UNIT ADJUST
3.7 V RF L40
Top [DIAL]
panel
600 mA RF R16
1.5 W Top [DIAL]
panel
85 % RF R554
30 % LOGIC R41
R16
Idling current
adjustment
CP1
PLL lock voltage
check point