From The 2Nd If To The Srif Output; 1St Mixer Of The Srx-1 Path - Kenwood TS-990S Service Manual

4-4. From the 2nd IF to the SRIF output

In FM mode, the signal is applied to the FM IC (IC602).
In modes other than FM, the signal is input to the AM/SSB/
CW/FSK/PSK mode mixer (D601 and D602) via D502.
The FM mode signal is mixed with SLO3 (10.240MHz) in
the FM discriminator (IC602) and converted into the 3rd IF
(455kHz). The 3rd IF signal passes through the ceramic fi l-
ters (CF602: wide, CF601: narrow), and is demodulated into
audio signals and amplifi ed by the FM AF AMP (IC603).
IF input
(10.695MHz/11.374MHz)
4-5. 1st Mixer
There are two 1st mixers used:
SRX-1 path: IF frequency=11.374MHz
SRX-2 path: IF frequency=73.095MHz
The 1st mixer for the SRX-1 path is a quad-balanced type
mixer which consists of Q351 to Q354 (JFET), where the
signal is mixed with the SLO1 (12.495MHz to 32.195MHz) at
a level of approximately 18 dBm and converted to the 1st IF
(11.374MHz). Approximately 2.6V bias is added to the SLO1
in order to suppress distortion.
RF
12.495~32.195MHz
CIRCUIT DESCRIPTION
IC602
FM FM IC
CF602
D502
Switching
455k BPF
BW: 12kHz
CF601
455k BPF
BW: 9kHz
AM/SSB/CW/FSK/PSK
D601,602
Sub RX 3rd Mixer
Fig. 19 From the 2nd IF to the SRIF output
L356
Q351
Q352
L357
SLO1
Fig. 20 1st mixer of the SRX-1 path
Signals other than in FM mode are mixed in the AM/
SSB/CW/FSK/PSK mode mixer (D601 and D602) with the
SLO3 (SRX-1 path: 11.398MHz, SRX-2 path: 10.719MHz),
converted to the 3rd IF (24kHz), and amplifi ed by the 3rd IF
AMP (IC601).
Signals in FM or other modes are sent from the SRIF
connector (CN600) on the TX-RX unit (X57-827 A/2) to
CN670 on the DSP unit (X53-453).
IC603
FM AF AMP
IC604
Multiplexer
IC601
Sub RX 3rd IF AMP
The 1st mixer for the SRX-2 path is a quad-balanced type
mixer which consists of Q401 to Q404 (JFET), where the
signal is mixed with the SLO1 (73.120MHz to 133.095MHz)
at a level of approximately 10 dBm and converted to the 1st
IF (73.095MHz). No bias is applied to the SLO1.
The variable resistor (VR401) in the 1st mixer are used
to adjust the mixer balance. If you have replaced the FETs
(Q401 to Q404), transformers (L403, L404 and L406), vari-
able resistors (VR401), or TX-RX unit (X57-827 A/2), do the
1st mixer balance adjustment in adjustment mode.
+14V
Q353
L359
Q354
+2.6V
TS-990S
CN600
SRIF
To DSP unit CN670
(X53-453)
1st IF
11.374MHz
21