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FM R E C E I V E R A D J U S T M E N T S
Procedure:
1. Connect a sweep generator to the mixer input
of the FM receiver. Set the sweep generator
for a 10.7 MHz centered sweep.
2. Connect the sweep voltage output of the
sweep generator to the Channel 2 input jack of
the oscilloscope and set the oscilloscope con-
trols for external horizontal sweep ( S W E E P
T I M E / D I V to X - Y ) .
3. Connect
the
vertical
demodulator input of the FM receiver.
4. Adjust the oscilloscope vertical and horizontal.
gain controls for display similar to that shown
in Fig.23A
A
M A R K E R
G E N E R A T O R
R F
O S C
X-Y O P E R A T I O N A P P L I C A T I O N S
Phase Measurement:
Phase measurements may be made with an os-
cilloscope.
Typical applications
designed to produce a specific phase shift, and
measurement of phase
amplifiers or other audio networks. Distortion due
to non-linear amplification is also displayed in the
oscilloscope waveform
input
probe
to
the
S W E E P
G E N E R A T O R
M A R K E R
S W E E P
INPUT
R F OUT
V O L T A G E
M I X E R
I F
Fig. 2 3 Typical FM receiver alignment set-up
are in
circuits
shift distortion in audio
5. Set the marker generator precisely to
MHz.
The marker "pip"
center of the bandpass.
6. Align the IF amplifiers according to the ma-
nufacturer's specifications.
7. Move the probe to the demodulator output.
The " S " curve should be displayed, and the
1 0 7
MHz "pip" should appear exactly in the
center (see Fig. 2 3 B . )
Adjust
the
demodulator
manufacturer's
moves equal distance from the center as the
marker frequency is increased and decreased
equal amount from the 10.7 MHz center fre-
quency.
B
V E R T I C A L
S I Z E
D E M O D U -
L A T O R
A M P S
F M
R E C E I V E R
A sine wave input is applied to the audio circuit be-
ing tested. The same sine wave input is applied to
the vertical input of the oscilloscope, and the out-
put of the tested circuit is applied to the horizontal
input of the oscilloscope. The amount of phase
difference
between
calculated from the resulting waveform. To make
p h a s e
m e a s u r e m e n t s ,
procedures (refer to Fig. 24).
should be in the
according
to
instructions
so the
marker
—
X
Y
H O R I Z O I N T A L
S I Z E
D I R E C T
A U D I O
A M P S
the
two
signals can be
u s i n g
t h e
f o l l o w i n g
10.7
the
21
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