Philips PM5324, Instruction Manual

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29
3. 1 . 6. 1 . 1 . C rystal oscillator
( F ig. 27)
The active el ements of the oscillator are Nand-gates N3 and N4 included in integrated circuit 32 1 . V ia resistor
644 both gates N3 and N4 function as analogue inverters wh ich are positively fedback via quartz-crystal 752
a nd adjustable load capacitance 542//543. The quartz-crystal which functions as absorption circuit is adjusted
to exactly 1 0 M H z with trimmer 542. N and-gates N 1 and N2 (also included in i ntegrated circu it 32 1 ) serve as
sine-wave/square-wave pulse former a nd decouple the osc i l l ator from the first decimal divider 322 a nd the mixer.
If button CA L has not been depressed, inverter N 4 is blocked via input G 8 and oscil l ating is stopped.
l
Fig.
27.
Crystal oscillator
3. 1 .6. 1 .2. Decimal dividers
32'
•
---0
3
2
:3 t. :. " MAino
The first 1 0/ 1 divider is included in integrated circuit 322. I f button CAL is depressed, a 1 M Hz signal and its
many harmonics is available at the output of this d ivider. This signal is supplied d i rectly to the second 1 0/ 1
divider (323) and via R C network 649//550 to the mixer.
The second 1 0/ 1 divider supplies a 0. 1 MHz signal to the mixer via R C network 650//55 1 .
Depending on the selected frequency range the decimal dividers are b l ocked or not; the 1 0 M Hz oscil l ator
functions always if button CAL is depressed .
Frequency range
. 1 . . . .3 and .3 . . . 1
1 3 and 3 . . . 1 0
1 0 30 and 30 . . . 80
75 . . , 1 1 0
.4 . . . . 5
1 0.3 . . . 1 1 . 1
3. 1 . 6.2. M ixer
Decimal divider
322 and 323 functions
322
functions
322 a nd 323 functions
322 and 323 functions
The mixer consists of biased diode 409. To this d iode the next signals a re suppl ied :
- the h.f. signa l , via separating transistor 3 1 2 a nd network 646//545, 647 and 648//547
- the 1 M H z signal
- the 0. 1 MHz s ignal