Kenwood TK-190 Service Manual page 18

TK-190
9. Compander circuit
The term compander is a compound of compressor and
expander. The compander reduces noise by utilizing a com-
pressor and an expander.
As shown in Fig. 14, the signal input to the compressor is
compressed so that the logarithmic ratio is 1/2 with refer-
ence to –10dBV, and then output onto the transmission
path. The signal is expanded by the expander so that the
10. Option Board Terminal
Terminals for mounting the option board are provided at
the bottom of the TX-RX unit. The table below shows the
correspondence between the board and terminals. Discon-
18
CIRCUIT DESCRIPTION
(dB)
Compressor Transmission path
0
Signal
–20
–40
Noise
Input
–60
–80
–100
Modulator
Input
Compressor and
Transmitter
X57-608X-XX
Component side
DATI CODE4
C471
DATO
CODE2
C469
TCNT
C470 STONE
TXOUT
AUDIH
E
MUTE NC
SCALL
R674
AUX
PTTIO
KEY
R481
RXAEN
MAND
EMERG
BUSY TXIN
PTT
R470
A+
9
R471
C472
16
logarithmic ratio is 2 with reference to –10dBV. This re-
duces noise on the transmission path and prevents deterio-
ration of the signal quality due to noise during transmission.
The TK-190 contains IC607 (TC35453F) to perform this
operation.
Pin 16 : Compressor input pin
Pin 18 : Compressor output pin
Pin 43 : Expander input pin
Pin 41 : Expander output pin
Expander
40dB S/N
Demodulator
and Expander
Receiver
Fig. 14
nect R414 and R665 in TX-RX unit when the voice scrambler
board is attached.
Connect the option board to the connection terminals of
the TX-RX unit.
23
C467
C466
CODE3
C464
CODE1
C462
C461
RXOUT
C468
C456
E
CLR/C
C458
RXIN
9
+V
8
1
Fig. 15
0
–20
–40
Output
–60
–80
60dB S/N
–100
Output
C657
R415
R412
R653
R652
C667
Q602
C654
R661
C647
12
22
L603
11
1
33
34
44
C633 C632
L602 R645 C627
Q404
R414
C646
C644
R660
R654
C640
C638
C637
C634
C635
R640
R666
C400