TS-440S
CIRCUIT DESCRIPTION
Sig n als from the A NT pin are fed into the RAT pin of the R F
unit via the transmit/receive switching relay. The signals then
go to the 1 0 BPFs through th
�
approx . 20 d B attenuator cir
cuit, the first stage of the first IF trap circuit, and the low
pass filters (which pass only 500 kHz or less). The signal then
goes through the second stage of the fi rst IF trap circu it, and
is mixed with the VC O sig nal and converted into the first IF
sig nal of 4 5 . 0 5 MHz in the first mixer, consisting of 03 and
04 (2SK 1 2 5- 5) . The VC O circuit con sists of 02 1 to 024
( 2SC 2668Y) and oscillates in four bands from 4 5 . 0 5 MHz
to 7 5 . 0 5 MHz . Oscillator freq uencies a re controlled by D C
sig n als from the PLL u nit .
The first IF sig n al of 4 5 . 0 5 MHz is passed through the M C F
(F 1 ) , which is used i n both receive and transmit, and i s am
plified by the fi rst IF amplifier 05 ( 3S K74L) . In the second
mixer, consisting of 06 and 07 ( 2 S K 1 2 5), the first IF sig nal
is mixed with the hete rodyne oscillator sig nal ( 36 . 2 2 MHz)
from the PLL circuit, amplified by 0 1 2 (2SC 2668Y) to ob
tain the second IF sig n al ( 8 . 8 3 MHz) . The second IF sig nal
of 8 . 8 3 MHz goes through the g ate of the noise bla nker . In
modes other than FM , the signal then g oes through the MCF
(F2) and is fed into the IF u nit through buffer amplifiers 08
and 09 (2SC 2668Y).
1
)
Selectivity circuit
Fig u re 4 is a selectivity c ircuit diagram. In auto mode, the
appropriate bandwidth filter is automatically selected accord
ing to mod e . When an optional filter is used, two filters are
availa ble . Ta bles 2 and 3 shows the various combinations
"?if'
DIO
C25
DI D2
D3
'7'1f"'
1
To
02
;;i;
0
l
a.63MHz IF SECTION
from ICIO
455KHz IF SECTION
,.._
,.._
0
F•T
from ICJO
SSB
BBS
BBC
BBW
455
45A
When the optional 8 . 83 MHz fi lter is connected, the second
IF sig nal is then fed from the IF u nit into the optional filter .
In the thi rd mixer, consisting o f 0 1 and 02 ( 3SK73G R), the
second IF signal is mixed with 8 . 37 5 MHz sig n a l generated
by IF u nit ' s heterodyne oscillator circu it, consisting of 0 5 3
and 054 (2SC2458Y), and converted into the third I F sig nal
(455 kHz) . The third IF signal is then ampl ified by 05
(3SK73GR). A diode switch is used to route the sig nal to
either the FM or SSB circuits.
In SSS mode, the thi rd IF signal goes through the S SB cer
amic filter (XF 3). In AM mode, the third IF signal goes through
the AM ceramic filter (XF4) . In either mode, the third IF sig
nal is then amplified by 07 and 08 ( 3SK73G R) and detected.
In FM mode, the thi rd IF s i g n al goes through the FM ceramic
filter (XF 5). The s i g n al is then sent to the FM IF, IC 2 ( MC
3 3 57) for amplification and d etection . IC 2 also contains a n
F M noise squelch circuit .
The detected SSB/A M signal is passed through the notch cir
cuit, consisting of hybrid IC IC 1 (BX6 1 24) and squelch g ate
0 1 2 ( 2SC 2 4 5 9BL) . The sig nal then g oes through the AF
volume control and is amplified to the appropriate level by
AF amplifier IC7 (UPC 200 2V).
of bandwidth availa ble when optional filters a re used . In F M
mode, the selectivity switch does not operate a n d a si ngle
dedicated F M filter is used . O ption a l fi lters operate only in
receive and are sepa rate from the filters used i n transmit .
45A
BBS
455
BBC
AUTO SELECTIVITY CONTROL
L_
______
__J
,---------,
Dll
I
I
AUT
from
JCIO
Fig . 4 Selectivity control circuit
MANUAL SELECTIVITY CONTROL
7
