Table of Contents
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LnT31072
DESCRIPT ION
Channe.l CrrarC is
disabled
when
the
microphone
js
removed
from the
hookswitch.
EXTERNAL
SPEAKER
(OpTTONAL)
A five-inch
speaker, contained in
a
LFXANo
housing, provides an audio output of
3 watts.
The
nomina
I speaker
impedance
is
3.2 ohms.
The speaker
leads are
connected
to
pin-s
3
and
7 of
Systems
plug P910.
IVhen
the
Externa
I Speaker is used, the
jumper
from
H13
to
H14
on the (IOC) board can
be
removed
or
P904
unplugged
to disconnect
the
hui
I
t-in speaker.
A
LEXANo
bracket is
sup-
p) j
ed for
moun
t
i
ng.
OPERATION
Complete operating instructions
for
the
Two-lVay
Radio are provided in a
sepa-
rate Operatorts Manual. The basic
proce-
dures for
receiving
and transmitting
messa
ges
fo
1
1
ows
:
TC
RECEIVE
A
}.4ESSAGE
1. Turn the radio on by pushing
in
the
POWER
pushbutton.
2.
Push
in the
I,{ONITOR
button to dis-
able the squelch circuit
and
Chan-
nel
Gua
rd decoder.
Adjust
the
volume control for a comfortable
I
istening level and then
release
the
I\{ONITOR
but
ton
f
or
norma
1
operation.
The radjo is now ready to
receive
messages
from other radios in the
system.
TO
TFANSI4IT
A
I\,IESSAGE
'|
Turn the radio on as clirected in
the "To Receive a
lr,lessage" sec-
tion.
2. Press the
PTT
switch on the
micro-
phone and speak
across the face of
the
nnicrophone
jn a normal
voice
level.
Release
the
PTT
switch
as
soon
a
s
t
he
messa
ge
ha
s
been
given.
The
red inriicator
I
ight
on
the control panel will
glovr
eacb
tirne the
microphone PTT
switch is
pressed,
inr!icating
that
the
transmitter is on the air.
The
receiver is
rnuted when
the trans-
mitter is
keyed.
INITIAL
ADJUSTMENT
After the radio
has been
installed
(as
described in the Installation
I\4anual), the
following adjustments should be
made
by
an
2
electronics technician
who
holds a Firsl
or.
Second Class
FCC
Radiotelephone license
(where requi
red
)
.
TRANSTI
I
TTER
ADJUSTIVIENT
Adjustments for the
Lransmi
tter
in-
clude measuring the forward and reflected
power and
adjusting the antenna length for
optimum VSIJR,
then setting the transmitter
to rated
power
output.
Next,
measuring the
frequency and modulation and entering
these
mea
suremen t
s on the
FCC requi
red
sta
t
ion
records.
For the complete transmitter
ad-
justment, refer to the Alignment
Procedure
(see Table of Contents).
RECEIVER
ADJUSTMENT
The initial
adjustment for the recei-
ver includes tuning the input circuit
to
match the antenna.
For the Receiver
Ad-
justment Procedure, refer to the
Alignment
Procedure (see Table
of
Contents).
CHANNEL GUARD DISABLE
All radios are equipped with
Channel
Guard.
1n
applications
where Channel
Guard
is not desired, disable the
Channel
Guard
circuit
by connecting a jumper from
J910-B
to J910-9. Also,
remove
the versatone if
present.
RE-
INSTALLATION
If
the mobile combinati.on is ever
moved
to a different vehicle, always
check
the battery potarity of the
new system.
CIRCUIT
ANALYSIS
TRANS}{I TTER
The transmitters
utilize
a crystal
control led, frequency modulated exciter for
two-frequency operation in the
4bO-4TO
trtiHz
frequency band. The solid state transmit-
ter uses integrated circuits
and discrete
components
for increased reliability.
The
transmitter
consists of audio processor
U1O1;
osci
I
1a
tor Q151, and Q15t, buffer
Q153,
exciter stages e201 through
e2O4;
pA
ampl
i fier
Q251 through Q253, and
power
control circuit
q2S4 through e287.
The
exciter provides approximately 150 milli-
wa
t
ts of
modula
ted RF to the pA
which
provides rated output power. Figure 1 is
a
block
diagram
of the radio
showing
both
the
transmitter and receiver.
I\{ICROPHONE
PREATIPLIFIER
A preamplifier
stage
(e901
and
associated circuitry)
is provided for
the
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