Icom IC-720A Instruction Manual page 23

MODE/FREQUENCY display.
In SSB operation there is both an USB (upper side band)
and an LSB (lower side band). USB is selected on the
10MHz band and above, and LSB on the 9MHz band and
below, in the SSB-N setting. When you wish to operate on
the opposite sideband, push the FUNCTION switch first,
then SSB switch.
When you wish to operate on а band other than the 15MHz
band, push the BAND UP/DOWN switches to select the
band you wish to operate. Slowly turn the AF gain control
clockwise to a comfortable level. Rotate the tuning knob
until a signal is received. The multi-function meter needle
will move according to the signal strength, so tune for the
highest possible meter reading and the clearest audio.
Refer to 5-2-2 ~ 5 on page 16 for other functions,
5-3-1 on page 17 for CW reception, 5-4-1 on page 18
for RTTY reception, and 5-5-1 on page 19 for AM
reception.
When you wish to receive on 1.599.9MHz and below, con-
nect a low band antenna to the LOW BAND ANT terminal
on the rear panel. Refer to 5 - 7 - 6 on page 21.
5-7 OTHER OPERATIONS
5-7-1 METER FUNCTIONS |
The multi-function meter functions as ап S-meter in the
receive mode, and as the following in the transmit mode,
depending on combinations of the METER SELECT switch
on the front panel, and the METER and SWR switches
under the access cover.
RF meter : Indicates the relative output power оп the Ро
scale.
ALC meter : Indicates the ALC condition.
Ic meter : Indicates the collector current of the final
transistors.
SWR meter : Indicates the VSWR of the load on the SWR
scale.
The combinations of the switch positions for the meter
functions are as per the following chart.
METER
SELECT
SWITCH
METER
SWITCH
RF
5-7-2 VSWR READING
The IC-720A has a built-in VSWR meter for checking an-
METER
FUNCTION
RF meter
SWR SET
ALC meter ALC
іс meter RF
SWR meter
(calibrating)
SWR meter
(measuring)
SWR SET
_20—
tenna matching іп order to avoid problems caused by
VSWR. Set the METER SELECT switch and METER
switch to the RF positions, and the SWR switch to the
SWR SET position as shown in chart 5 - 7 - 1. Set the op-
erating mode to RTTY, and push the TRANSMIT/RE-
CEIVE switch to TRANSMIT.
Adjust the SWR SET control located under the access cover
so that the meter needle points to "SET" on the meter
scale. Set the SWR switch to the SWR position. With the
switch іп the SWR position, SWR reading can be seen оп the
meter. Although this unit is built to handle VSWR of up to
2:1, it is recommended that the antenna(s) be adjusted for
the lowest possible VSWR. After taking the reading, return
the switch to the SWR SET position. ALSO BE SURE
THAT THE ANTENNA IMPEDANCE 15 50 OHMS OR
THERE MAY NOT BE ANY OUTPUT. OTHERWISE
THERE WILL BE DAMAGE TO THE TRANSCEIVER.
The final transistors used in the ІС-720А are of good design
and аге protected to a reasonable extent by circuits
incorporated in the set. These devices can be expected to
have an indefinite lifetime since there are no cathodes to
burn out. Under some conditions, however, they can be
abused beyond tolerance and may have to be replaced.
When in doubt about antenna systems, use the lowest
power setting possible to achieve meaningful readings. Use
a good tuner or transmatch when necessary. Always use
Caution and exercise judgement when testing RF power
generators.
5-7-3 WWV RECEPTION
To receive WWV (or other standard frequency station}, set
the operating band to 10MHz in the HAM band mode, and
the MODE to any mode. Tune to 10.000.0MHz on the
frequency display.
Since the IC-720A has a General Coverage receiver built-in,
any frequency's WWV can be received. Merely set to the
GENERAL COVERAGE mode and USB or CW, and tune
to the desired frequency.
The WWV signal сап be used for alignment of a frequency
counter, marker oscillator, or the frequency display.
5-7-4 SIMPLE FREQUENCY ALIGNMENT
A very accurate frequency counter is necessary to align the
frequency of the IC-720A. However, the frequency can be
aligned simply by receiving the WWV signal.
. Set the frequency display to 10.000.0MHz in the HAM
band and be sure that you are receiving the WWV signal.
. Set the operating mode to CW. A 800Hz beat can be
heard.