Sony CRF-150 - Page 7

if stage󰾰 سأ
чае
у ESE
Fig. 1:3 Block diagram of the sw front end
Age
amp
‘The
age
(automatic
gain
control)
0202
Circuit
consists
of
transistor
0302
Q202
and
diode
0302.
The
carrier from the last stage of the
if amplifier adds a negative арс
voltage on the positively-biased
base of transistor Q202 through
diode
D302
as
shown
in
Fig.
1-4.
озо!
В 0
m
Me,
mal
6
ome
07
gal
d
Fig.
1-5
Output
waveform
of
the
age
ud
M
Strip
P
Ist
mixer
Q301
combines
the
signal
озо!
applied
to
its
base
with
the
oscil-
—
lator
voltage
(1.55
-
2.25
MHz
higher than incoming signal)
applied to its emitter for conver
sion to the 1.55 — 2.25 MHz Ist
Fig. 1-4 Diagram of the age
Аз the signal becomes stronger, Е
the age level becomes higher SW tst м 0303 amplifies three am sig-
sito:
amplifier.
mals;
1.55
2.25
MHz
(SWI
—
decortindy;
the;
collier
SWIO),
$20
—
1,670
kHz
(MW),
current
of
Q202
and
the
drain-
MW,
LW
rf
254 145
410
kB
(LW):
current
of
0201
decrease.
If
amplifier
the signal is small, 0202 0303
increases the gain of rf amplifier
Q201
and
the
desired
sensitivity
2nd
oscillator
0304
generates
a
frequency
455
is
obtained
as
shown
in
Fig.
1-5.
0304
kHz
higher
than
the
signals
that
In
this
way,
the
gain
is
controlled
come
from
0303.
automatically.
Fm
if
Q302
amplifies
the
10.7
MHz
1st
focal
‘The
oscillator
generates
a
fre-
amplifier
fm
if
signal
coupled
through
quency
1.55
—
2.25
MHz
higher
0302
ceramic
filters
CF301
and
than
the
incoming
signal
fre-
CF302.
Also,
the
saturation
quency,
and
injects
the
gener-
due
to
high
base
to
emitter
bias
ated
voltage
at
the
emitter
of
clips
the
negative
peak
of
the
Q301.
Тһе
oscillator
fre-
ac
signal
voltage
developed
at
quencies
are
fixed
in
each
band.
the
collector
of
Q302.