Yaesu FT-902DM Instruction Manual page 31
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Also See for FT-902DM:
- Instruction manual (57 pages) ,
- Survival manual (37 pages) ,
- Instruction manual (5 pages)
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The VOX
GAIN
control VR,
on the front panel
provides
adjustment
for
relay
sensitivity,
and
VReo;,
controls
antitrip
sensitivity.
Relay
hold
time is determined by delay control VR6o2-
The tone oscillator Q¢; .(2SC1815GR)operates when
the MODE
switch
is in the CW
position. It is a
phase
shift oscillator
operating
at approximately
800 Hz. The sidetone level is adjusted by VReo3.-
The sidetone
output is also coupled
to the VOX
circuit for semi-break-in operation.
Located
on
the VOX
UNIT,
the crystal
marker
generator Q,,, (2SC1815Y) generates a basic 3200
kHz crystal controlled signal which is divided into
100
kHz
multiples
by frequency
divider
Q6;2
(4024PC).
The
voltage
regulator
Qgo5
(2SC
1815Y)
regulates the supply voltage to the VOX
circuit.
FM UNIT (PB-1707B)
The speech signal from pin 200f PB-1707B is fed
to amplifier limiter Qg99
(TA7061 AP), which clips
both
positive and negative
peaks when
they ex-
ceed
the level set for maximum
deviation of the
transmitier
frequency.
Qo;9
(2SCL815Y)
acts as
an active
low pass filter to eliminate
harmonics
caused
by
the
clipping.
VRog2.
determines
the
maximum deviation.
The
output
from
Qo9,
is amplified
by
Qo,
(2SK34E)
and then fed to the modulator
Dogg
(FC63).
Qo,
(2SCI815Y)
oscillates at a crystal
frequency
of 8987.5
kHz and is frequency mod-
ulated by varactor diode Dogg. The output from
Qo12
is amplified by Q 9,3 (2SCI81SY) and then
fed to the NB UNIT.
TUNE UNIT (PB-1720B)
When
TUNE
switch S,,9,
is pushed, the voltage
across
C3,;9,
is applied
to the
base
of Qy401
(2SCI815Y),
causing
Q3;9;
to
turn
ON;
this
activates
RL ,92
which
grounds
the cathodes of
Daji05
and
Day9¢6
(both
181555).
As Dyyo5
is
connected
in parallel
with
the PTT
switch,
the
transceiver is placed in the transmit mode.
Diode
Dz;9¢
grounds
the common
terminal
of
the
MODE
switch
S,g and
S,h,
and
the
bias
voltage of the PA stage is lowered
from the cut-
otf condition to the normal operating level.
"PB (728A __
% KEYER UNIT
t— ol
es
Q
x
x
ede
ILE F
TUNE,CW
KEYING
CIRCUIT
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