Discrimi Nator Curve - Philips PM5324 Instruction Manual

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2.3.4.2.2. IF band· pass filter
- Connect the h . f.·generator to the connection point g iven in the documentation of the receiver. The earth
connection of the h . f.·cable must be con nected as short as possib l e to the point to wh ich the signa l is supp l ied .
- Set the volume contro l of the receiver to m i nim u m .
- Set t h e tun i ng t o t h e long wave end.
- Set the receiver to f. m.
- Screw out the cores of the i .f. band·pass filters as far as possible; note the adjust i ng proced u re, i f necessary.
- U nsolder the e l ectrolytic capacitor in the ratio detector (C5, F ig. 1 6).
- Adjust the core of the primary c i rcuit of the ratio·detector to maximum a nd sym m etry of the band-pass curve,
so that the top of the curve at 1 0. 7 M H z i s on l i ne EF ( F ig. 1 8).
- Solder the e l ectrol ytic capacitor ( C5, F i g . 1 6) aga i n .
- Set t h e volume control o f t h e receiver t o maximum.
- Adjust the core of the secondary c i rcuit of the ratio detector to max imum defl ection of the i nd icator.
- Check the discriminator curve
.Connect the osc i l l oscope to C4/ R 2 ( F ig. 1 6)
.The zero passage of the band-pass curve should be in th e centre of the p icture ( F ig. 1 9 )
.The centre o f the straight part o f the curve should b e o n l i ne E F ( F ig . 1 9)
. I f the curve has an asymmetrical or non- l i near shape, repeat the procedure from 2 .3 .4.2.2.
U nsolder the electrolytic capacitor (C5, F ig . 1 6) aga i n
-
- Adjust the cores o f the other band-pass filters to maximum height o f the curve i n the sequence i nd icated in
the trimming table ( F ig. 20, curve I ) . The band-pass curve must always be symmetrical with respect to. mid·
screen ( E F , Fig. 20)
- Checking the a . m . suppression
.Solder the el ectrol ytic capacitor ( C5, F ig. 1 6) agai n
•
Press button A M l l kHz
•
The picture on the osc i l loscope shows a sinusoidal m od u lation. The a m p l i tude of th is mod u l ation l ies
between zero ( i n the middle of the d iscriminator curve) and a certa i n value (at the end of the stra ight part
of the curve). The a . m . suppression is su fficient, if the ampl itude at the e!}ds is sm a l l e r than 1 / 1 0 of th e
height of the curve.
2.3.4.2.3. R F-, I F and oscillator circuits
- Connect the indicator across resistor R3 of the ratio detector via a resistor of 0. 1 M n ( R4, F ig. 1 6 ).
- Connect h . f. generator PM 5324 to the f.m. aerial sockets via impedance transform er PM 9537.
- Turn the vo l u m e control to m i n i m u m .
- Set t h e receiver t o f. m.
- Tu ne to h ighest frequency.
- Adjust the receiver and h . f. generator to the frequency ind icated i n the tri m m i ng table.
- Adjust the cores of the
sequence indicated i n the trimm ing tabl e .
2 00 kHz
��II- -- -
Fig. 19. Discriminator curve
d.-,
i . f.- and osc i l l ator circuits to maximum deflection of the i nd icator in the
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Fig. 20. IF band -pass curves