Sharp GF-780H - FM IF;RF ADJUSTMENT

Figure 16-4 FM RF
G:;)
o
Electronic
Voltmeter
Oscilloscope
Figure 16-3 S CURVE
Rod Antenna
GND
Figure 16-1 FM IF
ICl
0.011.11" <D PIN
10.7 MHz
Dummy
(See Figure 16-6)
Figure 16-2 IF CURVE
10.7 MHz
I'M Sweep
Generator
®
FM IF/RF ADJUSTMENT
SWITCH
I'M mono
POSITION
SIGNAL
400Hz, 30%, I'M modulated
GENERATOR
TEST FRE-
DIAL AD-
STEP
STAGE
QUENCY
POINTER JUST- REMARKS
SETTING MENT
1. Using a minus
driver, turn
the core of
T2 counter-
clockwise
1
IF 10.7
MHz High
T1 before taking
frequency
it out of the
bobbin.
2.
Adjust for
best "IF"
curve.
2
Dstec-
T2 Adjust for best
tion
US" curve.
3 Repeat steps 1 and 2 until no further improvement can
be made,
4 87.3
Lowest L3
Band
MHz frequency
I-
coverege
5 108.3 Highest
TC2
MHz
frequency Adjust for
maximal
6
88 MHz 88 MHz
L2
output.
I-
Tracking
7
108
MHz 108 MHz TCl
8
Repeat steps 4, 5 and 6, 7 until no further improvement can
be made.
Rod
Antenna
t
VCO FREQUENCY ADJUSTMENT
SIGNAL
400 Hz, 30%, I'M modulated
GENERATOR
(mono signal)
DIAL
FREQUENCY POINTER
ADJUST- REMARKS
SETTING MENT
I'M mono position
I'M stereo position
(unrnodulatedl
98 MHz at 98 MHz VRl
Adjust for
60dB
38.00 kHz ±100 Hz.
Dummy
(See Figure 16-6)
Figure 16-5 VCO FREQUENCY
Rl
,.--- __ -'VVIr--4'P>To Telescopic Rod Antenna
R2
'------Ei-----To Chassis GND
Z
=75 ohms<Rl = 37.5 ohms
R2
= 75 ohms
Z
= 50 ohms<Rl = 50 ohms
R2
= 50 ohms
Z:
Output Impedance of Signal Generator
Figure 16-6 FM DUMMY
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