Kenwood TS-440S Serivce Manual page 5

TS-440S
CIRCUIT DESCRIPTIO N
ANT
Fig . 2 PLL frequency configuratio n
30 K
30MHz 1st MIX
MIX
3rd MI X
2nd
D
AF OU T
DET
/ \
I
5 KHZ
I
6 .22MHZ
P
D
120KHZI
1= 1800 1=450 1
J=72441=1811 1
FM MOD
I
/
1
I
HI
IPLL 5 1
I I F M
MIX 5
4 .55MH
AMR,FM R
AMT, FMT : 455 KH z
USB, CW : 456. 5
LSB, FSK : 453 . 5
CA R
1/1 0
IX 4
9.9—10 4MH
1/2 0
1/ 5
IPLL
31
I/1 0
MKR —
(=13720_ .20719)
11
RIT, XI T
Y
I/L
11/1800
L=19800
`_ MN614 7
20799
4
P.D
99=104MH z
(98_6 =103.6MHZ)
—
5KHZ
—
I
M=323 9
299 4
STEP 5
)Cw R
1
/P
o r
I
/P-
I
F
P
I/1
--- - 7006 J
58.25-u
53.25MHz
BP F
r
1
I p,D
I/ M
}
20KH Z
1/450
AM,FM
: 91 MH z
USB,CW : 91 .3 MH z
LSB,FSK : 90 .7MHz
IPLL4I
I
AM,FM : K=18200
USB, CW K=1826 0
LSB,FSK
K=1814 0
IPLL
11
D
I/N,I/A--L
1
8
SOOKHZ
INT=13-.73
T _ MN614 7
NT=PN-A
L— —
I
91 MH z
/'
—
1
I .98^-2.08MHz
64.78 =
59 .88MHz
P .D
5KH z
I/K
1/180 0
—
As shown in figure 2, all received frequencies excluding th e
local oscillator frequency fLo are generated in the PLL circuit .
The frequencies generated in these loops are expressed a s
follows:
-fsTD
VC04 :
f
K04
4
800 • . fvco4 = 7200 fSTD
. . . 3
.fsTD
L
VCO3 : fvLos =
4
800
fvcos = 7200 fSTD . . . . 4
fvcoz + fvco3 + fvco4 1
'fsTD
50 20 4
M 45 0
M fsTD
fvco _ s
fvco4
5
fvcoz = 1800
50
2 0
VC01 :
N 1 8
: .
fvcos = 72 fSTD + fLo + fSTD f
1
0 0 2 . . 6
Based on these formulas, the frequencies fvcor fHET, and fCA R
are expressed as follows :
/ N M L
fvco = fvcor = ( 72
1800 + 3600000
K
+ 1440000 + 1) fsTD + fLo 7
J
fHET = fVCO5 = 41 fSTD
8
Formula 1 may now be rewritten as follows :
N _ M L J
fIN 1 72 180000 + 3600000
41 + 1 ) . fsTD
1 0
Note that f L
o is
not included in formula 10 . That is, a
received frequency is determined by the reference frequen-
cy fs TD and frequency division data Ito N. Further analysi s
of formula 10 shows the following :
i) Basically, frequency division data I to N contain no er-
ror because they are controlled by the microproces-
sor according to the operating frequency .
ii) The accuracy of the operating frequency is equal t o
that of the reference frequency, because all frequen-
cies other than fs TD in formula 10 are determine d
by the microprocessor .
iii) The operating frequency does not change even if k o r
fLo changes .
When f IN = 14 MHz (USB mode) in formula 10 , f IN and
f STD have the following relationship :
VCO5 : fvcos
4 fsTD
fvcos = J I
4
1 fSTD
2
VCO2 :
fvcos — f L o — fSTD + fvcoz
1
f
10 4
sTD
fvco4
K
fcAR
200
1440000 fSTD 9
5