Kenwood TS-990S Service Manual

TS-990S
12
CIRCUIT DESCRIPTION
IF frequency IF fi lter
Mode
FM AM SSB FSK CW
8.248MHz
15kHz
*1 *1 *1
6kHz
*1 *1
2.7kHz *1
500Hz *1
270Hz *1
*1 : manually selectable
3-3. From the 2nd IF to the MRIF output
In FM mode, the signal passing through D30 is applied to
the FM IC (IC9) via D31. In modes other than FM, the signal
passing through D30 is input to the AM/SSB/CW/FSK/PSK
mode mixer (D32 and D33) via D31 (Refer to Fig. 7).
In FM mode, the FM signal is mixed with the MLO2
(7.793MHz) output in the FM wave detecting IC and con-
verted into the 2nd IF (455kHz). The 2nd IF signal passes
through the ceramic filters (CF1: 9kHz (narrow) and CF2:
Table 6 Selecting an IF fi lter
3-4. Preselector circuit
This transceiver has a preselector on the PRESEL unit
(X42-343 B/10). This function can be turned ON and OFF
with a panel switch.
The preselector forms narrow band-pass fi lters in which
inductors and capacitors are switched with relays for respec-
tive amateur bands. (Refer to Table 7.)
The fi lters cause an insertion loss of about 10 dB by the
band if the preselector function is used. This insertion loss is
compensated with the combined use of the variable attenua-
tor (ATT) in the PRESEL unit and the preselector AMP (Q10
and Q11) in the RX unit (X55-313 A/2).
12kHz (wide)), is demodulated into audio signals and ampli-
fi ed by the FM AF AMP (IC12).
Signals other than FM mode are mixed in the AM/SSB/
CW/FSK/PSK mode mixer (D32 and D33) with the MLO2
(8.224MHz) output, converted to the 2nd IF (24kHz), and
amplifi ed by the IF AMP (IC10).
These signals are output to the DSP unit (X53-453)
through the MRIF connector (CN137).
Fig. 7 From the 2nd IF to the MRIF output
CF1
455kHz BPF
BW: 9kHz (Narrow)
IC12
FM AF AMP
FM
(AF)
CF2
SSB, CW, AM,
FSK, PSK
D32,D33
2rd mixer
FM
IC9
FM IC
D31
Switching
IF input
(8.248MHz)
IC10
IF AMP
SSB, CW, AM,
FSK, PSK
(24kHz)
455kHz BPF
BW: 12kHz (Wide)
MRIF
CN137
24kHz
IC11
Multiplexer
Band Preselector operation frequency
1.8MHz 1.7975~2.00499MHz
3.5MHz 3.4925~4.01749MHz
5MHz 5.2400~5.46999MHz
7MHz 6.9800~7.33999MHz
10MHz 9.9800~10.17999MHz
14MHz 13.9500~14.44999MHz
18MHz 18.0180~18.26799MHz
21MHz 20.9000~21.69999MHz
24.9MHz 24.7900~25.18999MHz
28MHz 27.9000~29.89999MHz
Table 7 Preselector operation frequency

Kenwood TS-990S Specifications

General

Receiver Type	Triple Conversion Superheterodyne
Antenna Tuner	Built-in automatic antenna tuner
DSP	Yes
IF DSP	Yes
Modes	SSB, CW, AM, FM
Display	7-inch TFT color LCD
Weight	25 kg (55.1 lbs)
Antenna Connectors	SO-239
Power Supply	13.8V DC