Kenwood TH-F6A Service Manual page 11

4-1. A band reception
IC6 functions as A band reception PLL. This PLL IC controls
the VCO produced by Q34. VCOs are changed over by
switching the power provided to each VCO by Q35 through
control line "DAVCOS" from the CPU. VCO power passes
through a ripple filter consisting of Q31 and C235.
4-2. B band reception and transmission
IC2 functions as B band reception PLL. This PLL IC controls
the VCO produced by Q9. VCOs are changed over by switching
the power supplied to each VCO by Q10 through control line
"DBSS" from the CPU. VCO power passes through a ripple
filter consisting of Q7 and C52. Each VCO output is amplified
by a common amplifier (Q13).
4-2-1. 0.1MHz-267MHz reception, VHF (220MHz <K type
only>) band transmission
The VCO oscillator frequency is UHF. The signal output
from Q13 goes to the prescaler IC (IC3) and is divided into 1/8
(0.1MHz-23MHz), 1/4 (23MHz-104MHz), and 1/2 (104MHz-
267MHz). Division is controlled by using control signals "SW1
(Q15)" and "SW2 (Q15)" from the CPU. The division output is
amplified by an amplifier (Q19), and the signal goes to the
mixer (Q28) during reception and to the drive during
transmission. The PLL IC FIN input is generated by extracting
the output from Q13 and amplifying it with an amplifier (Q11).
VCO
B
AMP AMP AMP
Q2MT6C03AE
Q13
D18 HVC131 Q12
2SC
D11,12 2SC
HVC3758 5108(Y)
5009 5009
D21 HVC131
D10,16
HVC3758
AMP
MT6C
03AE
DEVIDER AMP
IC3
UPB
1509GV 5009
CIRCUIT DESCRIPTION
VCO
A
RIPPLE FILTER
SW
Q31
Q34
2SC4617(S) Q35
MT6C03AE
Q38 HNIJ02FU
D35,37
MA2S111 1SV305
D36,34
SHIFT SW MA25304
D40
Q70 2SJ243
HVC131
Q69 DTC144EE
PLL
IC6
LMX2326TMX
SW SW AMP
Q21 D99 D102 Q71
2SC HSC HSC 2SC4226
277 277 (R24)
Q93 D100
HSC
277
Lo
MIX
Q28
Q19 D101
MT6C
2SC HSC
03AE
277
Each VCO output is amplified by a common amplifier Q37.
In VHF/UHF band reception, the signal passes through a low-
pass filter, is amplified by Q40, then by a common local
amplifier (Q41), and goes to a mixer. This low-pass filter uses
a varicap (D28, D106) to shift cut-off frequency. The FIN input
to the PLL IC is taken from the Q40 output.
LPF
AMP AMP
Q37 Q40
2SC 2SC
5108(Y) 5009
TUNE
D28,106
HVC375B
Fig.15
4-2-2. 267MHz-707MHz reception, UHF transmission
The Q13 output goes to the mixer during reception and to
the drive during transmission. The PLL IC FIN input is
generated by extracting the output from Q13 and amplifying
it with an amplifier (Q11).
4-2-3. 707MHz-1.3GHz reception
Output signal from Q13 is amplified by an aplifier(Q11), then
the signal is multiplied by 2 by a multiplier (Q12). The signal
is then amplified with three amplifiers (Q21), and goes to the
mixer (Q28) during reception and to the drive (Q71) during
transmission. The FIN input of the PLL IC (IC2) is input by
taking the output from Q11.
AMP DRIVE AMP DRIVE AMP RF POWER AMP
Q72 Q54 Q56 Q55
2SC 2SK 2SK 2SK
5192 2973 2973 3476
Fig.16
TH-F6A/F7E
AMP MIX
Q41 Q45
2SC MT6C
5009 04AE
HPF SW HPF LPF
D53
UHF
D54
HVC131
LPF SW LPF
D49 D85
D50 D86
D51
VHF
D52
HVC131
BPF
ANT
11