Yaesu FT-902DM Instruction Manual page 30

cw
In th e CW , AM , and FSK modes, carrier oscillator
Q 7 0 2
( 2SK 1 9G R ) on the
a crystal control led carrier sign al of
T h e carrier is fe d through buffer amplifier
to the ring m odulator.
(2SC 1 81 5 Y )
fo r
oscillates TUN E operation .
DC vol tage is applied through diode switch
RL7 0 1 ,
(1 S l 5 5 5 ) and to unbalance the ring mod­
ula tor for CW, AM ,
resul ting carri er sign al is fed to T
The outpu t from
T 7 0 1
and fed to
(3 S K 5 9Y )
NB
UNIT. The signal is th en furth e r amplified
by Q 2 0 3 ( 3 SK 5 9G R ) , and is fed to th e transmitter
m i xer.
K eying o f th e transmitter is accomplished by
changing the bias voltage to
1
V
1 0 2 The tube s are cut o ff on "key up" by
.
applica tion o f - 3 5 V for
1 1 0 2 .
V 1 7 0 1
and V These cutoff vol t age are re­
-- 0. 1 V
duced to and
"key
d own" c onditions.
The key is connected to pin!
(PB 1 7 1 7A ) . Under "key d own" conditions, the
b ase o f Q 1 8 0 3
( 2 SA 733)
Q 1 8 0 5 (2SC 1 81 5 G R )
c o n duct. Th e voltage at pin
z e ro
when conducts. Since pin
Q 1 8 0 4
1 7 1 7 A
is connected to pin
the bias vol tage of
(PB- 1 7 08) ,
V 1 7 0 2
places these tubes in the n ormal operating
c ondition .
1 2
On other modes, volts is applied to pin 1 5 ,
causing Q 1 8 0 4 to c onduct, th us placing th e operat­
in g bias on the tubes.
KEYER UNIT ( P B- 1 7 28A )
The built-in electronic keyer utilizes
804 4 IC). The output of
"key d own" c on ditions ; th is output is connected
to the b ase o f Q 2 7 0 2 ( 2S C 1 81 5 Y ) ,
current of which is c onnecte d to th e base of
Q
1 8 0 3 , c au sing Q 1 8 0 3
d own" c onditions .
CARR UNIT generates
8 9 8 8 . 2
kHz .
Q 1 0 3
Q 7 0 2 also
0 9 1 2
and F S K operation ; the
.
7 0 1
is amplified by
Q 1 0 4
Q2 0 1 ( 2 SC 1 8 1 5 Y ) on the
V 1 6 0 1 , V 1 7 0 1 , and
- 1 O V
V 1 6 0 1 and l
- 6 0 V
, respec tively , during
of the U NIT
3 REC C
is groun d e d , causing
and Q 1 8 0 4 ( 2 SA639)
1 6 PB- 1 7 1 7 A
of reaches
1 6
o f
2
o f th e RECT A UNIT
V 1 6 0 1 , . Y 1 7 0 1 ,
(Cu rtis
02 7 0 1
02 7 0 1 is high during
the collector
to c onduct during "key
Keyer speed is controlled by
panel. V R2 7 0 1
space symme try , while
weigh t . V R 2 7 0 2
1 : 1
providing a
c w + sv
D O T
D A S H
I
I
I
I
V R 5 :>--- --�
VR 4
K E Y SW 2
3 ¢
6 ¢
L
_ -
for
AM
Th e microph one signal is amplified by
(TA7063P) and
Q704 ( 3 S K 5 9Y ) ,
kHz c arrier signal . The output from T
to the NB U NIT in the same manner as described
to
in the CW section previously .
PB-
FSK
and
T h e carrier oscillator
a crystal controlled carrier frequency of
kHz . When keying is applied to th e F S K jack J
th e b ase voltage o f
zero , c au sing
c ondition , Q7 0 1
circuit a n d l owering the c arrier frequency to
8 9 8 8 . 03
kH z .
AMGC circuit
.
circuit is l oc ated in tl-ie
Th e AM GC
U NI T and is used to reduce. th e gain of th e micro­
ph one amplifier when only l ow-level b ackground
noise is present (no speech inpu t f r om the opera-
- 2 8 -
V R 2 b on the fron t
provide s adjustment o f the dot­
adjusts th e keying
VR2 7 0 2
normally i s s e t to minimu m ,
d ot : space weight.
-
- - -PS:17z8A
KEYER uNIT !N"0.27�
S
0 0 2
2SCl815Y
a::
§ §
-
- - - - - - - - - - � -
Q7 1 0 (2SC 73 2T M )
whe re it modulates the
Q7 0 2 ( 2S K 1 9GR )
Q7 0 1 ( 2SC 1 81 5 Y )
Q7 0 1 to cut o ff. In the "space"
conducts, placing TC7 0 4 in the
11
I
I
i§
-1
Q I
� :
I
-
J
__
Q 1 o s
and fed tq
8 9 8 8. 2
7 0 2 is fed
generates
8 9 8 8 . 2
1 5 ,
becomes
CARRIER