Kenwood TS-440S Service Manual page 11

OS B by IC4 goes th roug h the SS B transmit switching diodes
0 1 7 a n d 0 1 8, filter switc hing diod es 0 1 4 a n d O 1 2, a n d S S B
ce ramic filter CF 1 , to o btain the S S B sig n a l . T h e S S B sig nal
the n goes through the tran smit switching diode 036 a n d is
fed into the tran smit first mixer, IC6, where the S S B sig nal
is mixed with the output from the 8 . 37 5 MHz os cillator in
the IF u nit, and converted to 8 . 8 3 MHz . In CW or F M mode,
the carrier sig nal from the P LL u nit does not g o through IC 5
B M or the 4 5 5 kHz filter. These ca rrie r sig n als a re a p plied
to IC6 via switching diodes 0 5 3 and 0 5 4 . The output sig nal
from IC6 goes through the MCF to remove s p u rious compo­
n e nts, and is amplified by the IF amplifier 046 ( 3S K7 3) a n d
s e n t to the RF u nit . 046 p rovid es ALC control a n d CW
keyin g .
I n the tra n smitter second mixer, consisting of O 1 1 a n d O 1 2,
( 3 S K 1 2 2), the 8 . 8 3 MHz tran smit IF sig nal i n p u t to the RF
u nit is mixed with H ET os cillator sig nal ( 36 . 2 2 MHz) from
the PLL u nit and converted to 4 5 . 0 5 MHz sig n als . The 4 5 . 0 5
MHz sig nal g o e s through D 2 3 a n d the M C F t o remove a n y
s p u rious compo n e nts . T h e 4 5 . 0 5 MHz sig nal the n g o e s
through D 27 a n d i s s u p plied to the tran smit third mixer cone
sisting of 0 1 3 a n d 0 1 4 ( 3 S K 1 22). In the third mixer the sig­
n al is mixed with VC O sig nal (02 1 to 0 2 4) amplified by 0 1 2
( 2S C 266 8) a n d converted to the requi red tran smit fre q u e n­
cy ( 1 . 8 to 29 . 7 MHz) . The sig nal from the third mixer goes
through the low pass filters C 1 56, C 1 5 8, C 1 59, a n d L 89,
a n d is amplified by the wid e band amplifier Q 1 5 ( 2 S C 2 570).
The sig nal then goes through the wide band tran sfo rme r T 1 9
and low pass filters C 1 64, C 1 6 5, a n d L90, and is further am­
plified by wid e b a n d amplifier 0 1 6 ( 2S C 2 5 3 8). The sig nal
from the 0 1 6 goes thro u g h the output transfo rme r T 2 0 and
is used a s the d rive output.
In F M mode, the PLL VC O is dire ctly mod ulated . The a u dio
sig nal from IF u nit IC4 (UPC 1 1 5 8HZ) is fed into the RF u nit
via the F M I pin . In the RF u nit, the a u dio sig nal is amplified
by 036 ( 2S C 2 4 59) a n d 037 ( 2 S C 260 3), a n d g oes through
the limite r circuit c o n sisting of 038 (UPC 4 5 5 8C) a n d low
pass filte r circ uit, and is sent to the PLL u nit via the FMD
pin . In the PLL u nit, the 36 . 2 2 MHz VC O is mod ulated . 0 39
( 2 S C 2603) is a switching circ uit to p revent the mod ulated
sig n als from being emitted from the PLL unit in a mode other
tha n F M .
F o r " S " model radios the output from the R F unit is
amplified to a 100 W power level by 01 (2SC207 5 ) , 02
and 03 (2SC2 5 09) , and 04 and 0 5 (2SC28 79) in the
final unit. The 1 00 W output goes through the LPFs which
differ by bands, and is sent as output to the antenna via the
AT unit and transmit/receive switching relay. SWR and
ALC detection is performed at the output of the LPFs
CIRCUIT DESCRIPTION
1 ) Anten n a tuner
The a nte n n a t u n e r o p e rates w h e n the A UTO/TH R U s witc h
i s in the A UTO position a n d the AT TU N E s witc h i s O N . T h e
antenna tuner i s d riven in the CW mode and power i s reduced
to 50 W by the microcomp uter rega rdless of the mode select­
ed before the AT TU N E switch w a s turned O N . The r a n g e
of ope rating freq u e n cies is d etermined by a mic rocomputer
prog ram, and is from 3 . 5 MHz to 30 MHz .
•
AT u n it o peration
Power transmitted by the final u nit passes through the cur­
rent a n d volt a g e d etecting transforme rs L 1 a n d L 2 using
to roidal cores . Current and voltage com p o n e nts d etected
by the transformers a re sup plied to pin s 9 a n d 1 3 of IC 2
for wave sha pin g a n d their phases a re compared by IC 3
H 0 1 0 1 3 1 . The output from pin 3 of IC 3 d e p e nds u p o n
the phase o f the voltage a n d c u rrent w a veforms a p plied
to IC 3 . The sig n a l from IC 3 pin 3 is sent to pins 1 0 a n d
1 5 o f buffe r I C IC 3 HD 1 0 1 2 5 . O u t p u t from p i n s 1 2 a n d
1 3 o f IC 3 goes t h rough level s hift Zener d i o d e s D 5 a n d
D6 to co ntrol the input circuit o f motor d rive I C IC 5
B A6 1 09U 2 . The output sig nal is used to d rive motor M 1
to a dj u st the varia ble c a p a cito r VC 1 s o that the pha se
diffe rence between volt a g e and curre nt com p o n e nts is
reduced .
The cu rrent a n d voltage compo n e nts output from the c u r­
rent a n d volt a g e d etecti n g transforme rs is also s u p plied
to the volt a g e compa rato r IC 1 NJM29030. The compa­
rator output is used by motor d rive IC IC6 B A6 1 09U 2 to
d rive moto r M2 to adjust variable c a p a cito r VC 2 so that
the amplitude difference is red uced . That is, the phase con­
trol v a ria ble c a p a citor VC 1 is c o ntrolled so that the c u r­
rent is in phase with the volt a g e a n d the voltage co ntrol
varia ble c a p a cito r VC 2 is controlled so that the amo u nt
of amplitude diffe rence betw e e n the c u rrent a n d voltage
is reduced ( S W R 1 , a n S W R of 1 to 1 , is obtained when
the cu rrent and voltage a re in p h a s e and the amo u nt of
amplitude difference is 0) . VC 1 a n d VC 2 a re d esig n ed to
ope rate i n d e p e n d e ntly of e a ch other, but sin ce phase
difference affects the amo u nt of amplit u d e difference a n d
vice versa, VC 1 a n d VC 2 will n o rmally rotate tog ethe r .
Forward a n d reflected waves detected by the filter u nit a re
converted to SWR control sig n als in the SWR a rithmetic cir­
cuit in the co ntrol u n it a n d a re s e nt to the ISW pin of the
AT u nit . Since the SWR co ntrol sig n als are c u rrent w ave­
fo rms, the sig n als a re converted from I to V wavefo rms by
IC 8 ( b /4) in the AT unit and to o btain the corresponding vol­
.
tage mod e SWR sig n als are g e n e rated . The SWR sig n als a re
the n fed into the S W R compa rato r IC 8 (C /4). T h e refere n c e
voltage p i n 9 of t h e IC 8 (C /4) is s u p plied with a volt a g e cor­
responding to an SWR of 1 . 2 5 to 1 via a pote ntiomete r .
The refore, w h e n the actual SWR val u e exceeds 1 . 2 5, pin 8
of SWR compa rator IC 8 ( C /4) is H, so t h e motor d rive vol­
tage control transisto r 05 t u r n s o n a n d the collector of 04
is s u p plied with voltage from pin 1 4S. The volta g e is also
used to turn the tuning LED o n . The inverted i n p u t pin of IC 8
(d /4) is s u p plied with tria n gula r waves generated by IC7, a n d
its no n-inverted i n p u t p i n i s supplied with the a bove SWR vol­
tage sig n als . As a result, as SWR lowe rs, IC 8 (d /4) outputs
TS-440 S
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