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TS-440S
CIRCUIT DESCRIPTIO
N
1
. Overview
•
The TS-440 is a triple conversion type transceiver, incor-
porating a general coverage receiver, which uses 45
.0
5
MHz as the first IF, 8
.83 MHz as the second IF, and 45
5
kHz as the third IF
.
•
The TS-440 is compact, but allows for installation of a
n
optional internal automatic antenna tuner operating in th
e
amateur band from 3
.5 MHz to 28 MHz and enables
a
wide range of antennas to be used
.
•
The TS-440 also contains a microprocessor-controlled dig-
ital PLL circuit which controls frequency in 10 Hz step
s
using a single crystal oscillator to implement high accura
-
cy and stable frequency control
.
•
The TS-440 has the following major features
:
(1)
Selectable VFOs
; VFO-A and VFO-
B
(2)
Direct frequency input using a numeric keypa
d
(3)
100-channel memory containing frequency band
,
and mode information (channel 90 to 99 for split fre
-
quency memory
)
(4)
Memory scan in 10 channel groups and two type
s
of program sca
n
(5)
RTTY (AFSK) mode availabl
e
(6)
Squelch circuit operational in all mode
s
(7)
Dual filters available to improve selectivity and SI
N
ratio (optional filter required
)
(8)
IF shift, audio notch, IF filter switching, and RF AT
T
functions for convenient interference reductio
n
(9)
Large heat sink and cooling fan (100 W) enabling u
p
to one-hour continious transmit operatio
n
(101 Full and semi break-in circuits for C
W
(1 1) External-computer controllable (optional interface re
-
quired
)
(12) Many easy-to-read meter functions such as th
e
received signal strength (s-meter), transmitter power
,
SWR, and ALC level
.
2
. Frequency Element
s
The TS-440 utilizes a triple conversion transmitter an
d
receiver
.
V
30K
f IN
RX MIX
1
30MHz ,
RX
TX
45
.05MHz RX MIX2
8
.83MHz
RX MIX3
455KHz
DE
T
DISCR I
RX OUTPU
T
TX MIX3
TX MIX
I
8
.83MH
z
TX MIX
2
SSB,CWT, AM,
FM, FSK
(FM MOD
)
:45
.O8^-75
.05MH
z
-CW R
:45
.0792-- 75
.0492 MHz
SS B
C
W
FS
K
'
AMR,FM
R
AMT,FMT
: 455KH
z
USB,
CW
:
456
.5
KH
z
-LSB,FSK
453
.5KH
z
FSK
AFS INPU
T
B
.M
.
SS
B
AM
MIC INPU
T
F
M
Fig
. 1
Frequency configuratio
n
The overall frequency configuration of the TS-440 is show
n
in Figure 1
. The incoming received signal (f,
N
l
is applied t
o
the ANT terminal
. This signal is mixed with the local oscilla-
tor signal (fvco) in RX MIX 1 to obtain the first IF frequen-
cy
. This signal is then mixed with the HET Oscillator signa
l
(fHET) in RX MIX 2, to obtain the 2nd IF frequency
. Th
e
resulting signal is then mixed with the second local oscilla
-
tor frequency (f
L
o) to obtain the 3rd IF frequency
. The sig-
nal is then combined with the CAR signal for detection
. f
i
N
is expressed mathematically as follows
:
fiN = fvco
fHEr – fLo
fcAlt
1
4