Yaesu FT-223 Mode d’emploi
THEOR
Y
OF
OPERA
TION
:;.ENERAL
i'unctional
operation
of
the
model
FT
-223
VHF
IFM
transceiver
s
ìllustrated
in
the
Block
Diagram,
Figure
6
lefer
to
the
schematic
diagram
for
the
circuit
description.
['be
transceiver
consista
of
a
crystal
controlled
transmitter
and
:eceiver
operating
on
any
of
the
23
channels
within
the
frequency
:ange
of
144
to
148
MHz.
In
addition
to
22
channels
which
are
;elected
by
the
CHANNEL
selector
switch,
one
"most-often-used"
:hannel
may
be
preset
for
ease
of
operation.
Solid
state
circuitry
s
employed
throughout
and
the
transceiver
is
designed
to
operate
rom
a
13.5
Volt
+lO
o/o
DC
negative
ground
power
source.
CRANSMITTER
SECTION
Che
transmitter
section
produces
an
FM
(phase
modulation
method)
Jutput
signal.
Che
audio
signal
from
the
microphone
is
amplified
by
an
integrated
:
ircuit
Q201
(TA706IAP)
which
works
as
arnplifier
and
an
IDC
Instantaneous
Deviation
Contro!)
circuìt.
The
IDC
circuit,
clips
lOth
positive
and
negative
peaks
when
they
exceed
a
predetermined
evel
to
li.Init
the
maximum
deviation
of
the
transmitter.
The
IDC
:ontrol,
VR202,
permits
the
deviation
to
be
adjusted,
and
is
nominally
actory
set
fora
deviation
of
+5kHz.
When
wide
band
transmission
s
desired,
VR202
must
be
readjusted
to
provide
a
maximum
deviation
•f +10
kHz.
FT-
223
BLOCK
OIAGRAM
The
tone
signa!
passes
through
a
low
pass
filter
by
uni
t 11c
11
c
0501
and
is
fed
to
0502,
NE567.
When
the
tone
signal
has
t}
same
frequency
as
preset
for
transmitting,
the
voltage
of
pi
of
0502
becomes
low
causing
0504,
2SC372Y
to
1
'0FF".
In
t
proper
bias
voltage
is
applied
to
0119
for
normal
operation.
Without
proper
tone
signal,
Q504
conducts,
removing
the
prc
bias
from
0119
to
disable
the
audio
circuit.
As
the
conventional
carrier
squelch
circuit
is
operative
wher
the
tane
squelch
is
switched
in,
the
busy
lamp
lights
up
when
any
carrier
is
received.
l SIV A )
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---------------
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(
TOJYE.
SQ
S W l
ICH)
TONE SQUELCH
<Pe
-r555A) OPTION
Figure
9
Figure
10
-
17
-
Downloaded
by
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1e
frequency
modulated
146
to
148
MHz
signal
is
amplified
by
Q210,
:c741,
Q211,
2SC730
and
Q212,
MRF212
and
applied
through
a
two
age
pi-network
to
the
antenn
a.
A
diode
D204,
1Sl88FM
rectifies
s
mall
portion
of
the
RF
output
and
applies
the
resultant
DC
voltage
the
meter
where
is
provid
es
an
indication
of
relat
i
ve
power
output
om
the
tr
ansm
itter.
The
meter
sensitivity
is
adjusted
by
VR204
Ld
it
is
set
for
indication
of
8
on
the
meter
scale
a t l O
watts
on
a
l
ohm
r
esisti
ve
load.
the
transmitter
is
keyed
without
an
antenna
conn
ec
t
ed,
or
ifa
high
\T'R
exists
in
the
antenna
syst
em
,
the
reflected
power
is
detected
rough
T210
and
a
diode
D207,
1Sl88FM
produces
DC
voltage.
~15,
2SC372Y
conducts
with
the
DC
voltage
applied
through
VR209
.uaing
Q216,
2SC3
72Y
to
decrease
its
collector
current.
Thus
,
e
emitter
voltage
of
Q217
,
2SA496(0)
is
lowered
causing
Ql,
:D313
to
decrease
current
and
the
supply
voltage
to
the
PA
amplifier
nz
is
low
ered
to
prevent
damage
of
the
transistor.
The
protection
vel
is
set
by
VR209.
This
circuit
is
also
used
to
switch
the
output
·
wer
down
to
l
watt
where
the
ID/LOW
switch
is
s
et
to
LOW
position.
1e
amou
nt
of
power
reduction
may
be
adjusted
by
VR208.
1e
antenn
a
change
-over
circuì
t
consista
of
the
switching
diodes
~05
and
D206,
Ml
301.
~CEIVE
R
SECTION
te
146
to
148
MHz
input
signal
from
the
antenna
is
am
plified
by
~T
QlOl,
3SK
40Mon
RF
board,
and
applied
through
five
hi-Q
)t-coupl
ed
resonators
to
the
first
mixer,
Q102,
3SK40M
.
...
di
Q,
Q
Q ,
a..
X,
a
..
Q,
Q,
Q
Figure
8
Top
View
14
-
~
l
·t
Downloaded
by
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C'he
limited
audio
signa!
is
applied
through
a
low-pass
filter
to
2202,
2SC372Y
where
it
is
amplified
and
applied
to
the
phase
modulator
-aractor
diade
D20l,
lS
1658.
The
low-
;
pass
filte:t
limits
the
transm.itt€
nodulation
spectr\.un
by
attenuating
frequencies
above
the
speech
range.
~he
oscillator,
Q203,
2SC372Y,
operates
on
the
crystal
frequency
o
generate
the
initial
RF
signal.
The
crystal
frequency
is
in
the
12
MH
·ange,
and
is
determined
as
follows:
Crysta1
Frequency
(MHz)
=
Output
Frequency
(MHz)
12
~rhnmer
capacitors
TC40l
through
TC423
permit
each
of
the
23
:rysta1s
to
be
individually
setto
frequency.
Output
from
Q203
is
.mplified
by
Q204,
2SC372Y,
and
applied
across
transformer
L203.
~he
audio
signal
from
Q202
varies
tl1.e
bias
applied
to
DZO l
and
>202,
in
turn
causing
the
capa
city
of
the
diodes
to
vary
in
accordance
rith
the
audio
voltage.
As
D201
and
T201
and
D202
and
T202
are
in
eries,
the
capacity
change
in
the
diade
effectively
changes
the
esonant
frequency
to
produce
a
phase
shift
at
an
audio
rate
in
:1e
input
of
Q205,
2SC372Y
in
the
exciter
stage.
'he
angu1ar
phase
shift
fronì
the
modulator
is
relatively
small,
1erefore
the
crystal
frequency
is
multiplied
twelve
times
to
obtain
1e
desired
deviation
at
the
output
frequency
of
144
to
148
MHz.
'he
nìodulated
12
MHz
signal
is
applied
through
the
buffer
amplifier
~205,
2SC372Y
to
the
multiplier
chain
consisting
of
a
doubler
Q206,
SC710D,
a
tripler
Q207,
2SC710D,
and
a
doubler
Q208,
2SC710D
·here
the
necessary
frequency
m~ltiplicatio-n
is
provided.
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Downloaded
by
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SC372Y
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NOTES.
l
ALL
RES1STORS
IN n
1/
4\11
±.10%
UNLESS
OTH
ERW
I.SE
NOTE
O.
21lLL
CA
PACITORS
IN"F
UNLESS
OTHERWISE
HOTEO
.
+*=- 16\IIV
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FT
-
223
CIR
CUIT
OIAGRAM
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