Frequency Configuration; Circuit Description - Kenwood TS-711A Instruction Manual

CIRCUIT DESCRIPTION
@ FREQUENCY CONFIGURATION
Reception uses a double conversion superheterodyne
_ system, in which the second IF (Intermediate Fre-
quency) differs according to the mode. Here, the signal
from the antenna is mixed with the PLL, (Phase Locked
Loop) local OSC, (Oscillator), signal in the first mixer
common to the respective modes and is then convert-
ed to the first IF at 30.265 MHz.
At this point, the first IF is separated between SSB/CW
and FM modes. In SSB/CW, it is mixed with a 40.96
MHz local OSC signal (4 times the TCXO frequency) in
the second mixer (Q34) and is converted to the second
IF at 10.695 MHz. Then, this IF is product detected
with a 10.6965 MHz carrier. In the FM mode, it is
mixed with the 30.72 MHz local OSC signal (3 times
the TCXO frequency) in the second mixer (Q36) and is
converted to the second IF at 455 kHz.
Then, this IF is detected.
In SSB/CW transmission, the SSB/CW signal 10.695
MHz is mixed with the 40.96 MHz local OSC signal (4
times the TCXO frequency) in the balanced mixer
(Q6/Q7) and is converted to a 30.265 MHz signal. It is
then mixed with the 113.735 — 117.725 PLL signal to
the transmission frequency. In FM, a 13.6533 MHz
X'tal OSC signal, used in place of the 40.96 MHz local
OSC signal is modulated and multiplied by 3 to a 40.96
MHz local OSC signal.
@ RF UNIT (X44-1620-01, 11)
Reception system
The signal input from the RA terminal enters the RF ampli-
fier (Q1) through the ATT circuit (-20 dB). The RF ampli-
fier uses GaAsFET 3SK129. The input uses a 2-pole heli-
cal and the output a 3-pole helical, thus obtaining the de-
sired bandwidth and skirt attenuation.
The input signal is converted in the receiving mixer, Q2:
C-MOSFET 3SK122 to the first IF 30.265 MHz. Then, the
first IF is converts to the RIF level signal through
the 2-stage MCF (Monolithic Crystal Filter) and is out-
put to the IF unit.
Transmission system
@ IF UNIT (X48-1400-00, 11)
Reception system
The reception system is generally devided into SSB/CW
and FM modes.
1) SSB/CW mode:
For AGC, the IF output of Q22 is taken through AGC
buffer Q24 (2SC2458), 023 controls the AGC voltage.
2) FM mode:
The RIF is input to mixer Q36
(2SC2668)
via gate-
grounded amplifier Q35 (2SK125).
For the local OSC
signal, 30.72 MHz is obtained by multiplying the PLL
10.24 MHz reference by 3-times (038).
There, the RIF signal is converted to the 455 kHz se-
cond IF.
This output is amplified via ceramic filter L31 in the IF
amplifiers, consisting of Q44 (TA7302P), Q45
(2SC2668) and 046 (uPC577H), and is then demodu-
lated by ceramic discriminator L34 (CFY455S).
The demodulated signal is filter separated between the
AF pre-amplifier
(Q49: 2SC2458)
and the squelch
noise amplifier Q53 and Q54. The "busy" lamp is con-
trolled by the squelch circuit and the center detection
circuit (Q47: uPC4558C).
To suppress ignition noise, a
"killer" circuit using Q62 is added and is controlled by
Q61.
3) Noise blanker:
Q41
noise amplifier the second IF output obtained by
mixing the 30.265 MHz first IF at 36.
It is switched
by 043. Q37 is a switching circuit to blank PLL reset
noise which would otherwise occurs every 20 kHz.
4) SSB squelch:
Transmission system
1) SSB and CW mode:
The audio signal from the AF unit is amplified in the mi-
crophone amplifier Q28 - 30 and sent to the balanced
modulator,
D16 (ND487C1
— 3R).
In CW mode, the
modulator is unbalanced by DC, and this carries signal
output from the modulator is used.
The double side-
band output is filtered by 3SK73 (GR) (SSB Xtal filter
L12) amplified by FET Q5: and mixed with the 40.96
MHz
output from
Q2 in balanced
mixer
Q6, Q7:
2SK161
(GR) for conversion by the TIF (transmit IF) sig-
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