Kenwood TS-940S Instruction Manual page 52

voc
HET
CARO
MKR
AFS
Fig.10-2
gital unit A via the keyboard.
The received signal, having passed through the second IF
filter, is applied to the third receiver mixer 07, 8 to be
mixed with the CAR2 signal (9.285 MHz) and then con-
verted to the third IF signal (455 kHz). The output is then
separated into two channels. One is connected to the
Control unit FIN terminal, and goes through IF amplifier
045 and third IF filter CF1 . It is then applied to limiter am-
plifiers IC11 and IC12 for amplitude limiting, and the out-
put applied to ceramic discriminators L 12 for FM detec-
tion. The detected output is supplied from the FMV ter-
minal to the IF unit for the FM mode signal via the de-
emphasis circuit and, at the same time, the noise com-
ponent near 40 kHz is eliminated. The signal is then con-
nected to the squelch circuit. noise amplifier 046 and
047, noise rectifier D80 and D81 and the comparator con-
sisting of IC13 2/2.
The above Control unit circuits function in all modes.
Therefore, one noise squelch system is employed. The
squelch control output mutes the IF unit audio amplifier via
the MTU terminal. (IF unit 028)
The third IF signal is amplified by 010 on the IF unit and is
then applied to the filter circuit as the third IF signal.
48
This filter circuit uses a ceramic filter CF1 with a 2.7 kHz
bandwidth for SSB (used also for wide CW /FSK and nar-
row AM) and ceramic filter CF2 with a 6 kHz bandwidth
for AM wide. As an option, the filter circuit provides for
use of either a CW 500 Hz crystal filter or 250 Hz band-
width filter. These three filter types are automatically se-
lected by information from Digital unit
A.
like the second IF
filters. The signal from the third IF filter is amplified by 01
and applied to the fourth receiver mixer to be mixed with
the 355 kHz (CARl - CAR3) signal and converted to the
fourth IF signal. The output is applied to 013 via the notch
filter circuit. This amplifier output is detected by either the
SSB/CW product detector or the AM detector. The de-
tected signal is applied to AF GAIN control via the squelch
gate 028 and preamplifier 029. In CW mode, it is also
possible to apply the signal through the AF TUNE circuit,
IC1 and IC2. The output of 03 is also applied to the AGC
circuit. The received AF signal from the AF GAIN control
is applied to the Control unit, where it is amplified by the
audio power amplifier IC15 and used to drive the speaker.