Belcom LS-202E - Page 16

8)
9)
AGC circuit
In the AGC circuit,
the
signal
from L203
is detected
by D203
and
204 to
reduce the sourve
voltage
of
0203
in order to
control the
gain
of 0101 and
204.
Meter circuit
In
F[,4,
the
S-meter
is driven
by the 2nd
lF
signal
from
pin
7 of
lC1 01
via lCl 02, D'l05
and 106.
In SSB,
the S-meter
is driven
by the detected
output
from D205,
206 and 208
via A206,
D211 and
212.
TRANSMITTER
SECTION
RF
Circuit
The VCO
frequency and
carrier
frequency
of
i0.695
N'4Hz are
mixed by
L317,
L316.
D304 and.
D305, and
then
amplified
bv
0304 after
filtering
through
L312,
L313
and
L314
bandpass
filter'
The signal
is further
amplified
by
0303,
0302 and
O301 to
the
specified
output
pov!€r
and
fed to the
antenna
through
bandpass
filter.
Microphone
Amplifier
In
FN,4, the voicesignal
from the microphone
isamplified
by
IC405
eliminating
frequency
higher
than 3
KHz. and
applied
to the
VCO
circuit
for frequency
modulation.
In SSB, the
voice signal
is amplified
by
O401 and
applied
to IC404
balanced
modulator
together
with
the
10.695
i\4Hz carrier
to
generate
a
DSB signal.
The unwanted
sideband
is
removed by
FLl02., and the
resultant SSB
signal
amplified
by
0104, before
being
mixed with
the
PLL
output
frequency
in D304 and
305.
The
output
from D304 and
305 is
now at
final frequency,
and
is am-
plified
by
0304, 303, 302
and 301
to the 2.5W
final level.
PTT Circuit
By depressing
5404
PTT
switch,
0402 activates
1C403 to
put
the
transceiver
in
transrnit
mode.
1l
2l
3)