Kenwood TS-711A Instruction Manual page 26

nal at 30.265 MHz. Then, the TIF signalis amplified by
FET O8: 3SK73 and sent to the RF unit. In CW mode,
keying controlled by Q32 and Q8 gate biases using -6V
and Q13 switching.
2) FM mode:
The carrier signal output from the unbalanced SSB mo-
dulator is used. Different from the SSB/CW mode is
that the local OSC signal used in FM for balanced
mixers Q6, Q7 is oscillated by X'tal OSC L4. This OSC
output is tripled 40.96 MHz. In the FM mode, +5 kHz
frequency deviation is obtained after tripling the direct
modulated X'tal OSC output.
3) Power control
The final output is detected, and the ALC (Automatic
Level Control) voltage is controlled by Q4 in the Display
unit (X54-1820-00). The ALC voltage is applied to the
second gates of FETs Q5 and Q8, by which the TIF level
is adjusted and then APC (Automatic Power Control) is
applied. In addition, the power control, in which two
pots are used, controls the G2 voltage of generator
buffer Q32, to counter excessive ALC at low power.
@ AF UNIT (X49-1180-00)
@ Microphone amplifier
The signal from the microphone is amplified by Q1
(2SC2459 (GR)), which is common to both FM and SSB
modes. In FM mode, the signal is subject to 6 DB/oct
pre-emphasis by 04 (1/2) (NJM45588S) and is amplified
by OP amplifier Q4 (2/2). Then, it is high-cut by active
LPF (Low Pass Filter) Q9 for -24 dB/oct via amplitude
limiter D8 (MC911) and applied as modulation to the
X'tal OSC in the IF unit.
In the SSB mode, the output from amplifier Q1 is impe-
dance-converted by emitter-follower Q3 (2SC2458 (Y))
and provided as modulation for the balanced modulator
in the IF unit through the microphone gain control on
the front panel.
The input signal to pin ANI of accessory terminal
ACC2, in the SSB/CW mode is mixed with the output of
microphone amplifier Q3 and is then input to the micro-
phone gain control. In the mode, it is input to amplifier
Q4, but not through the pre-emphasis circuit.
Further, Q2 is controlled by the signal input ot ACC2
pin MM to turn OFF amplifier Q1 for microphone mut-
ing.
@ Processor
When the processor SW is ON, the processor circuit
consisting of Q5, Q6 and Q7 is connected through tran-
sistor switch Q8. Q5 is an amplifier circuit with ALC.
The NFB (Negative Feed Back) signal from Q5 pin 3 is
amplified by Q7, detected by D5 and input for ALC at
pin 6. Then, the input if controlled by ALC output pin 5.
Q6, an FET switch, adjusts the SSB level to that which
has been previously adjusted in the FM mode.
26
@ Other circuits
Q11 is the AF PA. Transistor Q10 is an AF amplifier
through which the signal is supplied to ACC2. Q1-2 is
the CW side-tone OSC circuit. Q13 - Q16 forms the
CW semi-break-in circuit.
@ FINAL UNIT (X45-1380-11)
The drive signal from the RF unit is amplified up to 25W by
hybrid Q1:M57727.
It is then supplied to the antenna through the ANT switch
and the LPF for removal of harmonic component content.
In addition, ALC detection, RF meter, reflected power de-
tection and fan temperature detection circuits are provid-
ed. The RF meter circuit is a peakholding circuit in which
voltage doubler detection is used. The final PA hybrid is
protected in two ways. Reflected power VSWR is detect-
ed the antenna circuit and lowers the drive voltage by con-
trol of the ALC reference voltage to prevent damage to the
final PA bybrid. For the second protection circuit, thermis-
tor TH1 detects the final temperature to control the fan
and, prevent abnormal heating in the final unit PA.
@ AVR UNIT (X43-1490-11)
The AVR (Automatic Voltage Regulator) unit consists of
the rectifier and filter section and the AVR circuit section.
The AVR circuit section has 13.8V, 8V and 9V AVR cir-
cuits and a temperature protection circuit and a fan drive
circuit.
The 13.8V AVR circuit consists of Q1 - 04 and pass tran-
sistor, Q5. Transistor Q1, which controls 5 emitter, sup-
plies power (pin BB) which is separately rectified and fil-
tered.
The fan is switched by comparator Q10 (1/2) and Q11
after heat detection by thermistor TH1 in the Final unit.
The temperature protection circuit functions to stop trans-
mission if the transformer heats abnormally due to exces-
sive continuous transmission, etc. during AC operation.
The detection circuit, like the fan, turns OFF the AVR 9T.
(QV, trnasmit) output.
@ PLL UNIT (X50-1990-00, 11)
The PLL unit has a double loop configuration an output in
10 Hz steps and uses a 10.24 MHz TCXO (Temperature
Compensated Crystal Oscillator) (+3 ppm) as the refer-
ence OSC. 10 Hz step operation is achieved by dividing
the output of the 2 kHz comparison PLL (Loop B) by a
1/200 divider.
Digital tuning in 10 Hz steps is obtained by mixing that
division signal with the output of the 20 kHz comparison
PLL (Loop A).
In addition, the carrier OSC, which is located in the PPL
unit is configured to form and IF shift.
Loop B is a mixing type PPL. The VCO output operates
from 64 - 68 MHz (Q28: 2SK192A in Loop B and is
mixed in Q31 (SN16931P) with a 51.2 MHz signal. This
infection signal is derived by multiplying 10.24 MHz
5-times, in Q32 (2SC2668) via buffer amplifier Q29