Kenwood TS-120S Service Manual page 7

FUNCTIONAL DESCRIPTION
MIX(1)
Input
MIX(1)
Output
RX, TX
Frequency
14.5
~15.0
3.5
~40
7.0
~75
vco Divider
23.33
~ 23.83
24.33
~ 24.83
14.33
~ 14.83
14.33
~ 14.83
12.33
~ 12.83
15.83
~ 16.33
22.83
~ 23.33
29.83
~ 30.33
36.83
~ 37.33
24.33
~24.83
34.33
~35.83
34.33
~ 35.83
34.33
~35.83
34.33
~35.83
34.33
~ 35.83
14.0
~14.5
21.0
~21.5
28.0
~28.5
37.33
~ 37.83
37.83
~ 38.33
38.33
~ 38.83
28.5
~29.0
29.0
~29.5
29.5
~30.0
VFO OSCILLATOR
DIGITAL COUNTER
The TS-120 digital counter employs a VFO frequency coun-
ting system as shown in Fig. 3.
The VFO frequency is mixed with a 5 MHz signal obtained
from the reference oscillator chain by a 3SK73 (Q7) and is
coverted to a 1 MHz signal. This signal passes through the
LPF, is amplified, buffered and shaped into a square wave,
passes through the 0.1 second gate circuit and is applied to
the four-digit counter. The signa! is counted from 10 Hz to
100 kHz and fed to the preset counter deriving the carrier
output.
The 100 kHz order digit presents "5" or ''O" to display the
operating frequency.
The 1 MHz and 10 MHz order digits are composed by diode
matrix operating on bandswitch information.
(22.B3~23.83) (29.83~30.33) (36.83~38.83) (15.83~16.33) (12.33~12.83)
3.5 VCO
14,wwv VCO 2t vcO 28 VCO 7 vco
Vari-cap line
fc Approx. 10 MHz
VCO output
From Counter
{BCD signal)
Unlock detector
Phase detector
Butt
Q1 Q2 Q3 Q4 Q5
46 018) 46018) 7840) 46018) 46018),
> Buft
Y VY V Y Y 06
S$
Q
Q26
i)
35,7
14.33~14.83
ne
24.33~24 83
14,JuY
BPF >
4
. 34.33~3483
21,28
KI BPF >
VFO
§,5~ 6.0MHz
CAR
VCO OFF signal
Blanking signals
Fig. 2 TS-120 PLL circuit configuration