Locking On High Frequency Signals; Count-Down Operation; Single-Pulse Operation; Use As Adelay Generator - GENERAL RADIO COMPANY 1398-A Operating Instructions Manual

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T Y P E 1398-A P U L S E G E N E R A T O R
3.9 LOCKING ON HIGH FREQUENCY SIGNALS.
3.9.1 FREQUENCY DIVIDER ACTION.
If a n e x t e r n a l s i g n a l is applied t o t h e E X T DRIVE
binding p o s t s and t h e P R F s w i t c h is s e t t o one of t h e
numbered p o s i t i o n s , t h e internal oscillator of t h e T y p e
1398-A will lock on t h e external s i g n a l . F o r i n s t a n c e ,
if a 50-kc s i g n a l is applied a t t h e E X T DRIVE termin-
als and t h e P R F is s e t t o nearly 1 0 k c / s t h e main p u l s e
of t h e T y p e 1398-A c a n b e locked a t
t h e external
frequency of 50 kc/s. In other words, t h e p u l s e genera-
tor is operating a s a 5-to-l
frequency divider and
s u p p l i e s one output p u l s e for every five input p u l s e s .
T h e p u l s e generator c a n b e phase-locked i n t h i s manner
t o frequencies w e l l above t h e maximum prf of the inter-
n a l oscillator.
3.9.2 OBSERVATION WITH OSCILLOSCOPE.
T o observe t h e above a c t i o n , connect a n o s c i l l o -
s c o p e and a n audio-frequency generator t o t h e T y p e
1398-A a s described in paragraph 3.3.3. If p o s s i b l e ,
observe t h e waveform of t h e external generator on t h e
o s c i l l o s c o p e , together with t h e Type 1398-A output.
T h e n proceed a s follows
a. S e t t h e P R F switch t o 1 kc/s.
b. S e t t h e AF control fully c l o c k w i s e .
c . Set t h e e x t e r n a l generator t o 1 kc/s.
d. S e t t h e output amplitude of t h e external generator
t o minimum and then i n c r e a s e it until t h e T y p e
1398-A l o c k s
.
e . S e t the frequency of the e x t e r n a l generator t o
2 k c / s , 3 k c / s ,
4
k c / s , e t c . , and e a c h time a d v a n c e
the s i g n a l amplitude t o lock the pulse generator. In
t h i s way t h e pulse generator c a n b e locked a t very
high ratios.
3.10 COUNT-DOWN OPERATION.
When t h e duration is s e t longer than t h e p u l s e
period, t h e p u l s e timing c i r c u i t s will " c o u n t down
",
producing one p u l s e for e a c h 2 , 3 , 4 ,
...
n input periods.
In general, t h e pulse duration will not be p r e c i s e l y
controllable, owing t o lack of recovery time.
3.11 SINGLE-PULSE OPERATION.
3.11.1 METHODS.
T h e r e a r e three ways by which one c a n produce a
s i n g l e p u l s e :
(1.) By rotating t h e A F control with t h e P R F s w i t c h
s e t t o E X T DRIVE.
(2.) By touching t h e E X T DRIVE binding post.
(3.) By using t h e T y p e 1217-P2Single-Pulse Trigger.
T h e following three paragraphs explain e a c h
method in d e t a i l .
3.1 1.2 ROTATION OF AF CONTROL.
S e t t h e P R F switch t o E X T DRIVE and rotate t h e
AF control about 2 0 or 3 0 d e g r e e s clockwise from i t s
center position and then reverse the direction of rota-
tion. An output pulse will b e produced a s the AF con-
trol is moved counterclockwise p a s t the center position.
Very little rotation is n e c e s s a r y t o r e s e t and t o s t a r t t h e
input c i r c u i t s . Be careful not t o touch t h e E X T DRIVE
binding post b e c a u s e a pulse burst may be produced by
t h e injected hum.
3.11.3 TOUCHING EXT DRIVE BINDING POST.
S e t the P R F s w i t c h t o E X T DRIVE and s e t t h e
AF control near t h e center of i t s range. A s i n g l e p u l s e
will be produced when the E X T DRIVE binding post is
touched. T h i s method is useful only for very long p u l s e s
b e c a u s e t h e driving s i g n a l is a burst of n o i s e or hum.
3.11.4 TYPE 1217-P2 SINGLE-PULSE TRIGGER.
T h e most convenient way t o produce single p u l s e s
is t o u s e a pushbutton actuating-circuit s u c h a s the
T y p e 1217-P2 Single-Pulse Trigger, shown pictorially
in F i g u r e 1-2 and schematically in Figure 3-7. T o u s e
i t , s e t t h e P R F switch t o E X T DRIVE and s e t the AF
control between three-quarters
clockwise and fully
c l o c k w i s e .
100 k n
1.5V
DRIVE
f
O.1LJF
O.'PF
TERMINAL
I
I
NORMALLY OPEN
- -
F i g u r e
3-7.
Schematic diagrom o f the
T y p e 1217-P2 Single-Pulse Trigger.
T o produce a main pulse when t h e s w i t c h opens,
connect t h e negative banana plug of the T y p e 1217-P2
(arrowhead terminal in Figure 3 - 7 ) t o t h e E X T DRIVE
binding p o s t of t h e T y p e 1398-A.
T o produce a main p u l s e when t h e s w i t c h c l o s e s ,
r e v e r s e the double banana plug of t h e T y p e 1217-P2 s o
t h e p o s i t i v e banana plug (ground symbol in Figure 3-7
)
is connected t o t h e E X T DRIVE binding p o s t of the
T y p e 1398-A.
3.12 USE AS
A
DELAY GENERATOR.
T h e delayed s y n c p u l s e from the Type 1398-A
c a n b e u s e d t o operate the input circuits of a second
T y p e 1398-A with a minimum of adjustment. T h e delayed

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