Transmitter Controls; And Switch - Icom IC-725 Instruction Manual

PRE-OPERATION
4
4-5
TRANSMITTER
CONTROLS
AND
SWITCH
TRANSMIT/ALC INDICATOR
Lights
up
when
transmitting. Lighting intensity
depends
on
the
mic
gain
and your
voice
level.
See
MIC GAIN
control
information below.
SPLIT
SWITCH
For
transmitting
on one frequency and
receiving
on
another. See detailed information
on
p.
21.
RF
POWER CONTROL
Varies the
RF
output
power from
10
W
to
maximum.
Adjust
this
control for the desired
output power
level.
Maximum
output power
•SSB
:
100
W
PEP
•
CW,
FM
:
100
W
•
AM
:
40
W
(AM
and
FM
operations require the optional UI-7
AM
•
FM
UNIT.)
MIC GAIN
Used
for adjusting the
mic
gain.
Adjust
this
control to the
point
where the
ALC
indicator lights
up
at
its
brightest level
while speaking
into
the
mic
using
your normal
voice
level.
See
ALC INDICATOR
information above.
Tech
Talk
from
Icom
Q:
What
is
ALC?
A:
ALC
means Automatic
Level Control.
The
ALC
circuit limits
output
power
by
controlling
the input
level
of the
RF
power
amplifier.
The
RF
power
amplifier
is
designed
as a linear
ajnplifier
to amplify an input
signal
proportionally.
The
linear amplifier functions
in
the linear area of
the
signal.
However,
if
the input
signal level
exceeds
the
limit
of
linearity,
the linear
amplifier
outputs
distorted signals
because the
signal
is
amplified
in a
non-linear area of
the
signal.
To
prevent transmitting distorted signals,
the
ALC
circuit detects a signal
and
applies
it
to
a
driver
amplifier
as
feedback
to
reduce driver
output power.
Therefore, the input
signal level
to the
RF power
amplifier
is
reduced and the transceiver transmits
clear signals.