Icom IC-720A Instruction Manual page 20

ВЕ POWER CONTROL
position until it "Click" ON.
Switch to transmit and turn the RF POWER CONTROL
counterclockwise while speaking into the microphone until
you obtain the desired RF "РЕАК" output power of bet-
ween 10 watts 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
Тһе ІС-720А 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 COUNTERCLOCKWISE
ANTI VOX CONTROL
FULLY COUNTERCLOCKWISE
VOX DELAY CONTROL
FULLY CLOCKWISE
Push the VOX switch on the front panel to the ON (in)
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 con-
trol counterclockwise makes the time shorter. Set it at a
position which is comfortable and which allows for short
pauses in normal speech.
Adjust the ANTI VOX control so that 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 SELECT Switch for CW
mode, or CW-N mode (first the FUNCTION key, then the
CW switch).
Other switches and knobs are set the same as for SSB
reception.
іп addition to the crystal band pass filter, a Narrow filter
(FL-32) is optional for this unit. When the MODE SELECT
Тит from the "COMP OFF"
—17—
Switch is set at the CW-N mode, this filter is activated and
the total selectivity of CW reception is improved (500Hz/
—6dB). 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 mode
will have the same selectivity as the CW mode.
The Pass Band Tuning system can be used to narrow the
band width up to 800Hz, the same as in the SSB mode.
Also, use the Noise Blanker, AGC switch and/or ATT switch
depending on the receiving conditions, the same as SSB
reception.
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
indicator is lit and shows that you are ready for CW trans-
mission. When you key the keyer, the meter needle moves
and your CW signal is transmitted. To decrease the trans-
mitting power, turn the RF POWER Control сошптегс!осК-
wise to ON and rotate to adjust while watching the meter
needle on the Po scale for the desired output power.
5-3-3 CW SIDE-TONE (MONITOR)
When keying the side-tone oscillator is activated and a
800Hz tone will be heard. The loudness of the tone is
controlled by the CW MONI Control located under the top
access cover. Rotating the control clockwise will increase
the loudness. This tone is also audible in the receive mode
and can be used for code practice, adjustment of the keyer,
etc.
5-3-4 SEMI BREAK-IN OPERATION
Тһе ІС-720А has Semi Break-In CW capability when using
the VOX function. When keying, the unit is automatically
set in the transmit mode. After keying, it is returned to the
receive mode, also automatically, after a given transmit-
release delay time constant. Leave the T/R switch in the
RECEIVE position, and set the VOX switch in the ON (IN)
position.
The transmit release delay time constant is set by adjusting
the CW DELAY Control located under the top access cover.
Turning the CW DELAY Control clockwise will make the
transmit release time longer. Set for your keying speed.