Functions Relating To Transmission; Modulation Input Path; Transmit Power Control - Kenwood TS-590SG Service Manual

n Transmit power control
Transmit power control is done in the same way as in the
previous models; the ALC circuit controls the ALC voltage
using the progressive wave voltage (VSF) and keeps a con-
stant output.
The voltage detected in the Final unit (X45-398 A/2) pro-
gressive wave voltage and reflection wave voltage (VSR)
detection circuits is sent to the TX-RX unit's (XC1-024 A/2)
CN5. The progressive wave voltage is the intended power
(100W, 20W) divided into a suitable voltage by the resis-
tance, and input into the differential amplifi ers consisting of
IC802.
The output voltage of IC802 (1/2) increases when the
progressive wave voltage rises, the current at the base
of Q803 increases thereby reduces the collector voltage
where the ALC time constant CR is connected. The reduc-
tion in this collector voltage reduces the output voltage of
the buffer (IC802 1/2), and the ALC voltage from the resis-
tance voltage divider drops. If the ALC voltage (2.5V when
the ALC voltage is not added) goes down, the IF amplifi er's
(Q952) second gate voltage goes down and the gain is de-
creased.
DAC (IC75, IC78) and ADC (IC83) Signal Path
n Outline
DAC (IC75) communicates signals with ACC2 and the
Optional unit (VGS-1). DAC (IC78) communicates signals
with USB. ADC (IC83) communicates signals with ACC2/
USB and the Optional unit (VGS-1). The signal path of DAC
(IC75, IC78) and ADC (IC83) vary depending on each sta-
tus of transmit/receive.
CIRCUIT DESCRIPTION
TX ATT TX IF Amp (ALC)
TGC
VSF
POWER
POC
CONTROL
AMC
VSR
VSWR
PROTECT
PRO
IC801 BA2904 (1/2)
ID
ID
PROTECT
IC801 BA2904 (2/2)
Fig. 13 Transmit power control
When transmitting AM, Q802 is turned on approximately
50ms after transmission, and the ALC voltage is controlled
with the average power. The input voltage of pin 2 of IC802
(1/2) used as the ALC reference voltage is controlled by
the adjustment value (POC) from the main MCU and output
from pin 5 of the D/A converter (IC13).
SWR protection is controlled by the reflection wave
voltage. The refl ection wave voltage is divided by the re-
sistance and input into IC801(1/2). If it exceeds the desig-
nated voltage, IC801(1/2)'s output controls the ALC voltage
and lowers the power.
The PWR (power) meter is amplifi ed from the progres-
sive wave voltage, the SWR meter is amplified from the
reflection wave voltage, and the ALC meter is amplified
from the ALC voltage each by the relevant operation ampli-
fi er and then input into the A/D converter and displayed on
each meter.
Q952
3SK264-5
ALC
ALC
IC802 BA2904 (1/2)
Q803 2SC4617(R)
IC802 BA2904 (2/2)
EXT ALC
n Functions relating to transmission

1) Modulation input path

Each output signal from the analog switch (IC80) passes
through the active fi lter (IC81) and then enters ADC (IC83)
and is sent to DSP (IC301).
 The signal sent from the USB (UAO) is output from pin 6
to pin 5 of the analog switch.
 The signal sent from the ACC2 (ANI) is output from pin 2
to pin 1 of the analog switch.
 The message output signal (VAO) from the Optional unit
(VGS-1) passes, without going through the analog switch,
through the active fi lter (IC82), and then input into ADC.
TS-590SG
17