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LBI-3999
CIRCUIT ANALYSIS
A-FET LEADS
I
B-TUBE EQUIVALENT
1
RC-1626
MIXER Q I
F i g u r e 2
-
FET Nomenclature
PLATE
(DRAIN)
RF from t h e a n t e n n a is c o u p l e d t h r o u g h
c a b l e W444 t o a t a p on L410/L412.
The t a p
is p o s i t i o n e d t o p r o v i d e t h e p r o p e r impe-
d a n c e match t o t h e a n t e n n a .
RF e n e r g y is
c o u p l e d t o L411/L413 t h r o u g h a n o p e n i n g i n
t h e s h i e l d w a l l , and t h e n t o t h e s o u r c e
t e r m i n a l o f FET
61.
61
o p e r a t e s a s a g r o u n d e d - g a t e a m p l i -
f i e r .
T h i s method of o p e r a t i o n p r o v i d e s a
low impedance i n p u t t o t h e a m p l i f i e r .
The
a m p l i f i e d o u t p u t is t a k e n from t h e d r a i n
t e r m i n a l and c o u p l e d t h r o u g h a t u n e d c i r c u i t
(C7 a n d L2/L3)
t o t h e i n p u t o f f i v e h e l i c a l
r e s o n a t o r s .
HELICAL RESONATORS
I n r e c e i v e r s w i t h o u t t h e UHS o p t i o n ,
t h e f r o n t e n d RF s e l e c t i v i t y
is
p r o v i d e d
by f i v e t u n e d h e l i c a l r e s o n a t o r s (L414IL419
t h r o u g h L418/L423).
RF c a b l e W441 c o n n e c t s
t h e RF s i g n a l from t h e a n t e n n a t o a t a p on
L414/L419.
The t a p is p o s i t i o n e d t o p r o -
v i d e t h e p r o p e r impedance match t o t h e an-
t e n n a .
The o u t p u t of L418/L423 is c o u p l e d
t h r o u g h c a p a c i t o r C1 t o t h e 1st m i x e r
a s s e m b l y .
1ST OSCILLATOR AND MULTIPLIER
R e c e i v e r Models 4ER42E10-33 a r e e q u i p -
p e d w i t h s t a n d a r d O s c i l l a t o r / M u l t i p l i e r
Boards A415-A420.
R e c e i v e r Models
4ER42G10-33
a r e e q u i p p e d w i t h O s c i l l a t o r /
M u l t i p l i e r B o a r d s which u s e t h e I n t e g r a t e d
C i r c u i t O s c i l l a t o r Module (ICOM)
.
S t a n d a r d O s c i l l a t o r / M u l t i p l i e r
Board
(A415
-
A4201
The o s c i l l a t o r i n t h e s t a n d a r d O s c i l l a -
t o r / M u l t i p l i e r Board is a t r a n s i s t o r i z e d
C o l p i t t s o s c i l l a t o r .
The o s c i l l a t o r c r y s t a l
o p e r a t e s i n a f u n d a m e n t a l mode a t a f re-
q u e n c y of a p p r o x i m a t e l y 1 6 t o 1 9 m e g a h e r t z .
The c r y s t a l
is
c u t t o p r o v i d e t e m p e r a t u r e
c o m p e n s a t i o n a t t h e h i g h e n d of t h e t e m p e r a -
t u r e r a n g e and
is
t h e r m i s t o r compensated a t
low t e m p e r a t u r e s .
T h i s p r o v i d e s i n s t a n t
warm-up w i t h a f r e q u e n c y s t a b i l i t y of
+0.0005% w i t h o u t c r y s t a l o v e n s o r w a r m e r s .
I n s i n g l e - f r e q u e n c y r e c e i v e r s , a jumper
from H 1 t o H2 c o n n e c t s r e g u l a t e d +10 v o l t s
t o t h e c r y s t a l c i r c u i t .
Feedback f o r t h e
o s c i l l a t o r
is
d e v e l o p e d a c r o s s C47.
I n m u l t i - f r e q u e n c y r e c e i v e r s , a d i o d e
is
c o n n e c t e d i n s e r i e s w i t h t h e c r y s t a l and
up t o t h r e e a d d i t i o n a l c r y s t a l c i r c u i t s c a n
be a d d e d .
The 1 0 - v o l t jumper is removed,
and t h e p r o p e r f r e q u e n c y
is
s e l e c t e d by
s w i t c h i n g t h e d e s i r e d c r y s t a l c i r c u i t t o +10
v o l t s by means of a f r e q u e n c y s e l e c t o r s w i t c h
on t h e c o n t r o l u n i t .
S w i t c h i n g t h e +10 v o l t s
t o t h e c r y s t a l c i r c u i t f o r w a r d b i a s e s t h e
d i o d e i n s e r i e s w i t h t h e d e s i r e d c r y s t a l ,
and t h e c r y s t a l f r e q u e n c y
is
a p p l i e d t o t h e
b a s e of o s c i l l a t o r t r a n s i s t o r
61.
The o s -
c i l l a t o r o u t p u t is c o u p l e d t h r o u g h C45 t o
t h e b a s e of 1st M u l t i p l i e r 6 2 .
The 1st m u l t i p l i e r o u t p u t is c o u p l e d
t h r o u g h T1/T2 t o M u l t i p l i e r Board A413/A414.
T1/T2 is t u n e d t o f o u r t i m e s t h e c r y s t a l
f r e q u e n c y .
The
1st
m u l t i p l i e r s t a g e is
m e t e r e d a t 5442-4 t h r o u g h m e t e r i n g n e t w o r k
C38, CR6, R17 and R18.
O s c i l l a t o r / M u l t i p l i e r Board With ICOM
(A432-A43 5)
O s c i l l a t o r / M u l t i p l i e r
B o a r d s A432-A435
u s e s ICOM Module Model 4EG26A10.
The ICOM module c o n s i s t s of a c r y s t a l - c o n -
t r o l l e d C o l p i t t s o s c i l l a t o r , a v o l t a g e r e g u -
l a t o r , and a b u f f e r o u t p u t s t a g e .
The e n -
t i r e module ( i n c l u d i n g c r y s t a l ) is e n c l o s e d
i n a d u s t - p r o o f
aluminum c a n , w i t h t h e ICOM
f r e q u e n c y and t h e r e c e i v e r o p e r a t i n g f r e -
q u e n c y p r i n t e d on t h e t o p .
A c c e s s t o t h e
o s c i l l a t o r t r i m m e r is o b t a i n e d by p r y i n g o f f
t h e p l a s t i c GE d e c a l on t h e t o p o f t h e c a n .
The o s c i l l a t o r f r e q u e n c y is t e m p e r a t u r e -
compensated a t b o t h e n d s of t h e t e m p e r a t u r e
r a n g e t o p r o v i d e i n s t a n t f r e q u e n c y compensa-
t i o n , w i t h a f r e q u e n c y s t a b i l i t y o f f 0 . 0 0 0 2 %
w i t h o u t c r y s t a l o v e n s o r w a r m e r s .
I n s i n g l e - f r e q u e n c y r e c e i v e r s , +10 v o l t s
f o r o p e r a t i n g t h e ICOM i s o b t a i n e d by a jump-
e r from
H 1 t o H2.
With t h e ICOM o p e r a t i n g ,
d i o d e CR1 is f o r w a r d b i a s e d a n d t h e o s c i l l a t o r
o u t p u t is a p p l i e d t o t h e
1st
m u l t i p l i e r Q1.
The 1st m u l t i p l i e r o u t p u t
is
c o u p l e d
t h r o u g h T1/T2 t o m u l t i p l i e r b o a r d A413/A414.
T1/T2
is
t u n e d t o f o u r
t i m e s
t h e ICOM f r e -
q u e n c y .
The
1st
m u l t i p l i e r s t a g e
is
m e t e r e d
a t 5442-4 t h r o u g h m e t e r i n g n e t w o r k C4, CR5,
R 5 and R6.
I n m u l t i - f r e q u e n c y
r e c e i v e r s , u p t o
t h r e e a d d i t i o n a l ICOM m o d u l e s c a n be p l u g g e d
i n t o t h e b o a r d .
The 1 0 - v o l t jumper is re-
moved and t h e p r o p e r f r e q u e n c y
is
s e l e c t e d
by s w i t c h i n g t h e d e s i r e d ICOM t o +10 v o l t s
by means o f a f r e q u e n c y s e l e c t o r s w i t c h on
t h e c o n t r o l u n i t .
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