Icom IC-751A - Section 7 Functions Operation; Vox Operation; Speech Compressor Operation

SECTION
7
FUNCTIONS
OPERATION
7
-
1
VOX OPERATION
1
)
Set
controls.
VOX
a
GAIN—
vox—DELAY
COMP
KEY SPEED
FULL
NB
WIDE
NB LEVEL
OFF
2)
Set the
T/R
SWITCH in the receive position.
3)
Adjust VOX GAIN
CONTROL.
4)
Adjust VOX
DELAY CONTROL.
5)
Adjust ANTI-VOX CONTROL.
The IC-751
A has a built-in
VOX
(voice-operated
relay)
circuit which
allows automatic
T/R
switching
by
using
the
operator's
speech
modulation.
1)
Set the VOX GAIN,
VOX
DELAY
and
MIC
GAIN
as shown In
the table.
SWITCH/CONTROL
POSITION
VOX SWITCH
ON
(IN)
VOX GAIN
FULLY
COUNTERCLOCKWISE
VOX DELAY
12
O'CLOCK
MIC GAIN
12 O'CLOCK
2)
Set the T/R SWITCH
in the receive
position. It is not necessary
to
push
the
PTT
SWITCH
on the microphone.
3)
Rotate
the VOX GAIN
CONTROL
clockwise while
speaking
into
the
microphone
until
the
T/R
switching circuit
activates. Stop
adjusting
the
control once
the circuit
has activated.
4)
The VOX DELAY CONTROL varies
the amount
of delay after
your speaking stops before the transceiver
changes back
to
the
receive mode. Rotate this control
counterclockwise
to
reduce
the time delay. Set it to allow for short pauses
in normal speech
without the IC-751 A changing
to
receive.
5)
Rotate the ANTI-VOX CONTROL on the
top pane! clockwise
while
receiving
a
signal until the
audio from the speaker no longer
activates the VOX circuit.
Refer
to SECTION
3
-
3
for the
con-
trol location.
7-2
SPEECH
COMPRESSOR
OPERATION
The IC-751 A has
a
low distortion,
RF
speech compressor circuit
which provides greater
talk
power by
improving the intelligibility
of
the
transmitted signal
over
long distances.
1)
Set
METER
SWITCH
to
"COMP" position.
METER
2)
Switch to
transmit and speak into
the mic.
1
)
Set
the switches and controls
as
shown in the table.
SWITCH/CONTROL
POSITION
MIC GAIN
CENTER
(12
O'CLOCK)
RF POWER
MAXIMUM
COUNTERCLOCKWISE
COMP ON (IN)
METER
COMP
2)
Switch
to
transmit
and turn the
RF POWER CONTROL
clock-
wise
while speaking into the
microphone until
the desired
RF
"PEAK" output
of between
approximately 10 watts
and 100
watts is obtained.
3)
Adjust the MIC GAIN CONTROL.
3)
Adjust the
MIC
GAIN
CONTROL
for
a
reading of
between
lOdB
and 20dB on
the COMPRESSOR
(COMP) scale.
4)
NOTE: Misadjustment
of
the
speech
com-
pressor may cause interference
to
other
stations.
4)
For the best
transmit audio,
leave the compressor
OFF, or use
a
low
mic gain setting
with the compressor
ON. However,
when in
contact
with DX stations, or
under weak
signal
conditions, the
compressor will definitely
improve
the readability of
your signal
when it is turned
on and adjusted
correctly.
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