Swann CUBIC ASTRO 102 BX Service Manual page 10

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NarE: Component designations used in the "Theory" sections of this manual
are the shortened numbers as they appear on the schematic diagrams. To de-
termine complete component designation, the boardjlocation numbermust
be
added after the letter or letters. See the "Note" in the first portion of
the "Parts" section of this manual.
Schematic diagrams contalned ~n the "Theory" sections of this manual
are simplified to help in the understanding of the operation of the circuit;
they may not always, therefore, be sufficient for troubleshooting purposes.
When servicing the equipment, it is urged that the technician use only the
schematic diagrams included in the "Servicing Data" portion of this manual.
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3-1
*CIIO
RECEIVE ANTENNA
IWITC" IN.
r - - - - - - - ....
D SWITCN - - - - - ,
I
LIQI LIQ2
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"It"
LlNI
TO RX elol ca
~
I"PUT
C>--ft--"'--1~
et-------oo
TO
Ut,
I 1101
"131 RI02
I
TO
_1Q1.
O! ..
BANIBWITCH AND LOW PASS FILTER BOARD
-- -- - - - - -
""'--..-;...;;;..
The received signal
from the antenna connec-
tor is passed through one
of six low pass filters,
which are also usedin
the transmit condition.
Each is composed of two
inductors and three cap-
acitors, yielding a five
pole filter for each band
(160 through 10 meters).
Note that the same filter
is used for all segments
of the 10 meter band.
The filters are sel-
ected
by
SlOl and Sl02,
sections of the BAND sw-
i tch. From SlOl, the
signal is passed to relay
KlOl, through C122, and
through ClOl. From there
it is routed to the input
of the preselector board.
Receiver antenna switch-
ing
is accomplished by KlOl ,
which is activated
by
Ql02.
When the receive ("R") line
is high, as it is in the re-
ceive condition Ql02 is bias-
ed to saturation, energizing
KlOl and connecting C122 to
the output of the selected
low pass filter. Since the
collector of Ql02 is low when
it is thus saturated, QlOl is
in a non-conducting condition
and has no effect. However,
when the "R" line is low, as