Kenwood TS-590S Service Manual Download Page 16

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TS-590S

The 10.695MHz transmission IF signal is converted to

73.095MHz by the mixer (D422, D423). The impedance is
made variable by the current that passes through the pin di-
ode (D741), and thus the level of the 73.095MHz transmis-
sion IF signal level changed. This level variance corrects the
transmission signal gain (PGC function) at the time of power
control.

Fig. 12 From transmission signal (TIF) to drive output

The transmission signal which passed MCF (XF371) with

the bandwidth 15kHz is converted to the target transmis-
sion frequency in the fi nal transmit mixer (IC761). This MCF
(XF371) helps reduce proximate spurious components. The
signal from the fi nal transmit mixer passes through the re-
ceive BPF, and is amplifi ed to the power needed to drive the
fi nal circuit in the drive amplifi er (Q783).

IC701

IC761

Q783

TIF

from DAC

(IC72)

Drive OUT

IC68

XF471

XF371

D741

Q721

D721
D722

D422
D423

10.695MHz

73.095MHz

LO3

ALC

LO2

LO1

■

From the drive output to the antenna terminal

The transmit signal sent from the TX-RX unit (X57-785

A/2) to the CN2 (TXRF) of the Final unit (X45-391 A/2) is
amplifi ed to the designated power in the fi nal stage, passes
through the LPF, and is then output from the antenna termi-
nal. This unit includes a relay antenna tuner circuit that oper-
ates in all bands.

The transmit signal input into the Final unit (X45-391 A/2)

CN2 is amplifi ed by the pre-drive amplifi er (Q1, Q2) and the
drive amplifier (Q3, Q4). Then, the signal's high harmonic
is eliminated in the LPF and the signal goes through the
progressive wave/reflected wave detection circuit, ampli-
tude phase detection circuit for the antenna tuner, transmit/
receive changeover relay (K46), antenna tuner IN/THROUGH
changeover relay (K45), antenna changeover relay (K44), and
fi nally, output through the ANT1 or ANT2 antenna terminal.
In order to reduce the transmit/receive changeover relay's
operational noise, relays are in a separate unit (X45-391 B/2).

Fig. 13 From the drive output to the antenna terminal

The antenna tuner tunes by the combination of the con-

denser and the coil. Its operation is the same as in previous
models. IC6's phase error signal switches the input side
condenser of the tuning circuit, and the IC5 amplitude differ-
ence signal switches the output side condenser. The SWR
is decided by calculating the voltage of the progressive
wave and the refl ected wave with the main MCU (X53-446
IC306).

This model includes a current protection circuit. The cur-

rent running in the fi nal portion is converted to the potential
difference of the 1m

resistance inserted into a power line,

and the potential difference is detected at IC4. When the
potential difference is larger than designated, IC4 output
activates the ALC protection function. This ALC protection
function controls so that the current would not exceed the
predetermined value when the current at the fi nal portion
is increased for some unexpected reason. There are other
protection circuits the same as the ones included in the pre-
vious models.

K46

X45 B/2

K45

K44

AT IN

Through

RAT

(TX-RX

unit)

VSR

VSF

IC6