From The If Amplifier To The 3Rd Mixer Output; From The 3Rd Mixer To The Scif; Scref; Pll To Sclo1/Sclo2 - Kenwood TS-990S Service Manual

SC08M
SC11S
SC73S
DDS

SCREF

6-3. MCF Adjustment
The MCF (XF1) is prepared for the 2nd IF frequency
(10.7MHz). Since the MCF terminal impedance is 1 k, the
impedance is converted using variable inductors. The MCF
is a filter that consists of a 2-pole MCF with a center fre-
quency of 10.7MHz and a passband width of 15kHz.
Connect an appropriate device, such as a tracking gen-
From 1st Mixer
10.7MHz
6-4. From the IF Amplifi er (SCIF2_AMP) to the 3rd
Mixer (SCMIX3) Output
In the 3rd mixer (SCMIX3), the signal is down converted
by the SCLO3, and converted to the 3rd IF (SCIF3: 24kHz).
6-5. From the 3rd Mixer (SCMIX3) to the SCIF
The 3rd IF (SCIF3: 24kHz) is amplifi ed by the OP ampli-
fi er (IC9) and sent to the control unit (X53-452) as SCIF.
6-6. SCREF
The scope unit has equipped two PLL and three DDS,
and it receives a 40MHz reference signal as SCREF from
the PLL (MAIN) unit (X50-322) in order to distribute approxi-
mately 8.4MHz reference signal to PLL (IC4, IC6) through
DDS (IC1, IC2).
After this 40MHz reference signal passes buffer amplifi er,
it is distributed to three DDS as master clock.
Approximately 8.4MHz reference signal generated
by DDS is inputted into each PLL of SCLO1 and SCLO2
through a ceramic fi lter. The signal for SCLO3 use is con-
CIRCUIT DESCRIPTION
ATT: 0dB
ATT: -10dB
ATT: -20dB
ATT: -30dB
PLL
Fig. 30 From the IF input stage to the SCIF (3rd IF)
Tune connector
CN10
L75 XF1
Fig. 31 MCF adjustment
MCF
ATT
ATT
PLL
ATT
DDS
ATT
erator, to the MCF adjustment connectors (CN10 and CN12)
and turn the variable inductors to adjust the MCF. Make the
MCF adjustments while in adjustment mode if you have
replaced the MCF (XF1), variable inductors, or scope unit
(X42-343 A/10). When adjusting the MCF, apply 8 V (8 A) to
the scope unit.
Tune connector
CN12
Supply 8V
L79
Q44,45
ver ted into 10.676MHz by the DDS and becomes the
SCLO3 signal via the amplifi er and fi lter.

6-7. PLL to SCLO1/SCLO2

■ SCLO1
The VCO consists of components including the induc-
tor (L60) and variable capacitance diode (D15). The PLL
(IC4) is in control of this VCO for the SCLO1 use. The VCO
outputs different oscillation frequencies (64.847MHz and
61.721MHz) for main signal reception and sub signal recep-
tion.
■ SCLO2
The VCO consists of components including the inductor
(L85) and variable capacitance diode (D23). The PLL (IC6)
is in control of this VCO for the SCLO2 use. This oscillation
frequency (83.795MHz) is changed by ±250kHz to perform
scope sweeping. It is performed every 10kHz by dividing the
bandwidth.
TS-990S
SFIC
DDS
To 3rd Mixer
29