2. FM-IF Alignment 10,7 MHz
Alignment Sequence
Wobbulator Output
connected to
Indicator Connection
Alignment
IF-Filter 3
IF-Filter 2 and 1
FM counter connection cable
Via clip-on probe with built in
diode connected to MP 303
(a) Put Out
(b) and (c)
to maximum and
symmetry
IF-Filter 3
(a)
to maximum and symmetry
(inner maximum)
3. FM-RF Alignment
a) FM Oscillator, filter and aerial circuit alignment
Generator
freq.
Input sensitivity 22,5kHz dev
1000Hz
Oscillator Voltage
pointer setting Oscillator
Filter circ.
Aerial circ.
6 db
26 db
1 W
Image
Rejection
At oscillator
emitter
At mixer
emitter
88 MHz
(A) Maximum
(C) Maximum (E) Maximum 0,60 uV 1,8 uV
0,7 uV
52 db
90… 100 mV 40… 50 mV
106 MHz
(B) Maximum
(D) Maximum (F) Maximum
0,65 uV 2,0 uV
2.0 uV
48 db
Note: Connect test transmitter with VHF signal (20 dB cable 60/150ohm, 22.5 kHz hub, 1 kHz module.) and adjust to the respective upper
maximum.
b) Adjustment of the display instrument at
FM
After performing the HF adjustment, set the pointer
deflection of the display instrument to "9" at 88 MHz and
an input voltage of > 1 mV with R 371.
c) Muting
Muting switch pressed. Feed in signal of 5 uV at the
antenna input at 88 MHz. Open R 366 until the signal can
be heard. Then slowly turn back the same controller until
the still tuning (muting) switches.
d) Checking the discriminator zero crossing
and the frequency display
After the HF adjustment has been carried out, with an
input voltage U9 >100 uV and f= 88.000 MHz, 88.00 MHz
must be set on the counter. At the same time measure
the voltage with a DC voltmeter on the MP 305 (IC 302
PIN 5). This value and the frequency display must not
change after switching on the AFC (observe the switch-
on delay). Otherwise, correct with the phase shift circuit
(F3).
4. Stereo Matching
Switch in "Stereo" position.
a) 19 kHz setting
Mute on, no signal. Connect counter to MP 306 (IC 303
pin 10) and set 19 kHz ± 1 kHz with R 377.
b) Stereo RF level
Test transmitter modulated at 19 kHz, 6 kHz deviation
at 88 MHz with 10 uV at antenna socket. Tune the
device precisely and slowly turn the R 384 from the
right stop until the stereo display lights up.
c) 57 kHz lock
FM station at 88MHz and one input signal
Modulate > 1 mV with 57 kHz (3.75 kHz deviation),
connect millivoltmeter to MP 304 (R 374) and set L 308
to minimum.
NOTES:
