Icom IC-720 Instruction Manual page 16

5-2-6 TRANSMITTING
Before transmitting, listen in the receive mode to make sure
your transmission will not interfere with other communi-
cations. If possible, use a dummy load for adjustment
instead of an antenna. Set knobs and switches as follows.
МІС GAIN CENTER
RF POWER CONTROL OFF (clockwise stil it ''clicks"')
METER SELECT SWITCH ALC
Other knobs and switches are left in the same positions as
for receiving. When the T/R switch is moved to transmit,
or when the PTT (push to talk) switch on the microphone
is depressed, the transmit LED is illuminated. By speaking
into the microphone, the meter needle will move according
to the strength of your voice and SSB signals will be
transmitted. Set the MIC Gain control so that the meter
needle stays well within the blue ALC zone at voice peaks.
Change to the receive mode by moving the T/R switch to
receive, or release the microphone PTT switch.
5-2-7 HOW TO USE THE SPEECH PROCESSOR
The Pass Band Tuning system acts as a low distortion RF
Speech Processor. This enables greater talk power and
better results in DX operation. Follow the steps below for
use of the RF Speech Processor:
Set to the CENTER
(12 o'clock) position.
Turn from the "СОМР" Off
position until it "Click" Оп.
MIC GAIN CONTROL
RF POWER CONTROL
Switch to transmit and turn the RF POWER CONTROL
counter clockwise while speaking into the microphone until
you obtain the desired RF "PEAK" output power of bet-
ween 10 watt and 100 watts (approximately).
Adjust the MIC GAIN CONTROL to a point where the RF
"AVERAGE" output power just saturates.
The Speech Processor should be turned OFF or MIC GAIN
CONTROL carefully set for minimum compression for all
communication other than DX operation for a very natural
voice quality.
5-2-8 HOW TO USE THE VOX CIRCUIT
The ІС-720 has a built-in VOX (voice operated relay) which
allows automatic T/R switching by voice signals into the
microphone. For VOX use, set the knobs inside the top
access cover as follows:
VOX GAIN CONTROL
FULLY COUNTER-CLOCKWISE
ANTI VOX CONTROL
FULLY COUNTER-CLOCKWISE
VOX DELAY CONTROL
FULLY CLOCKWISE
—14—
Push the VOX switch on the front panel to the on (їп)
position. Leaving the T/R switch in the receive position
and without pushing the PTT switch, turn the VOX gain
control clockwise while speaking into the microphone. At
a certain point, the T/R switching circuit will be activated
by your voice. This is the' proper position for the VOX
Gain control. Set the VOX Gain control at a level which
provides for T/R switching at your normal voice level.
Transmit-release time (the time delay before the set auto-
matically returns to receive when you stop talking) is
controlled by the VOX delay control. Turning the control
counter-clockwise makes the time shorter. Set it ata
position which is comfortable and which allows for short
pauses in normal speech.
Adjust the ANTI VOX control so Шар the VOX circuit is
not activated by sounds from the speaker by turning the
control clockwise while receiving a signal.
5-3 CW OPERATION
5-3-1 RECEIVING
For CW reception, PUSH the MODE Switch for CW or
CW-N position. Other switches and knobs are set the same
as for SSB reception.
In addition to a crystal band pass filter, a Narrow filter is
optional for this unit. When the MODE Select Switch is set
at the CW-N position, this filter is activated and the total
selectivity of CW reception is improved. Also, with this
filter, internal noise is reduced for comfortable CW
reception and an improved signal to noise (S/N) ratio.
If the optional CW filter is not installed the CW-N position
will have the same selectivity as the CW position.
5-3-2 TRANSMITTING
Insert the keyer plug into the KEY Jack on the rear panel
of the unit, and set knobs and switches as follows:
RF POWER CONTROL OFF (Fully clockwise)
METER SELECT SWITCH RF POSITION
Other knobs and switches are set the same as for CW
reception.
By setting the T/R switch to Transmit, the transmit LED
is lit and shows that you are ready for CW transmission.
When you key the keyer, the meter needle moves and your
CW signal is transmitted. To decrease the transmitting
power, turn the RF POWER Control counter clockwise to
on and rotate to adjust while watching the meter needle on
the Po scale for the desired output power.