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The modu lation signal i s adapted to resistor-diode network 664 u p to 669, 413 and 414 by em i tter fol lowers
3 1 4 and 3 1 5. The network serves to give a pre·d i storsion of the control voltage of the capacitance d iodes to
l i nearise their curve .so that the frequency change of the h.f. osc i l l ator i s proportional to the contro l l ing
modu lation voltage.
The capacitance diodes are d isconnectea trom the contro l l ing mod u l ation voltage source by resistors
602 a nd chokes 7 7 1
3. 1 . 4. 1 -kHz OSC I L LATO R
The active element of this R C osc i l lator is i ntegrated c ircu i t 32 1 . The frequency is determ i n ed by R C-fou r p o l e
6 2 6 - 506 / 628 - 507. The a m p l ifier consists of d ifference ampl ifier 321 / 1 , the output signal of w h i c h i s
su ppl ied to the mentioned R C fou r p o l e via em itter fol l ower 3 21 /1 1 .
The osc i l lator voltage is a lso suppl ied to a rectifier via resistor 622 and capacitor 508.
The rectifier consists of d iode 402 and transistor 32 1 / 1 1 1 w h ich is c i rcuited as a d iode . This recti fy i ng c i rcu i t
produces a control voltage to sta b i l ize the ampl itude. T h e output a m p l i tude may be adjusted by m e a n s of
potentiometer 632.
If button WOB. ( 803/6) is rel eased, the 1 kHz signal is ava i l able at connector 852
Moreover, the signal is supp l i ed to the ampl itude modul ator via resistor 62 1 , switch 803/2A a nd to the
frequency modulator via resistor 623, switch 803/5A, -/4A, -/3A, -/2 B and -/6A.
3. 1 . 5. SW E E P S I G N A L G E N E R ATOR AND BLAN K I N G P U L S E F O R M E R
The sweep signal generator consists o f a n e m i tter-coupled m u ltivibrator 30 1 /302.
The sweep signal is supp l i ed to difference ampl ifier 304/306, the em itters of which are a.c. coup l ed . Both
stages of the d ifference ampl ifier have a constant current sou rce (305 and 307) to obtai n a good common mode
rejecti o n . With d iode 401 the constant current sources are temperature compensated.
The sweep signal for frequency mod u l ation and a sawtooth voltage · phase s h i fted by 1 800 - a re taken from
col l ector resistors 6 1 1 and 6 1 6.
The voltage across resistor 6 1 1 can be adjusted with potentiometer 602 on behalf of the freq uency sweep.
The voltage across resistor 6 1 6 i s avai lable at connector 1 k H z/SW E E P OUT (852) for external co ntrol pu rposes.
Due to t h i s the mod u latioM voltage at connector 852 i ncreases s i m u l taneously with i ncreasi ng freq uenc ies.
The blanking pu lse, requ i red i n mode wobble, is taken from the col l ector of tra nsistor 302 and appl ied to
transistor 32 1 / I V which functions as a switch . If button W O B . ( 603/6) i s depressed the b l a n k i ng pulse is suppl ied
to b l a n k i n g diode 408 via voltage divider 609/6 1 0.
3. 1 . 6. CA L I B R ATOR
The cal i brator consists of a cal i brati ng osci l lator, a m ixer, a n LF ampl ifier w ith l im iter and ind icator.
3. 1 . 6. 1 . Cali brating oscillator
The ca l ibrati ng osc i l lator consists of a crystal osc i l lator and two decimal div iders.
,
772.
601
,
.
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