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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
+lOo/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
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