Icom ic-718 Instruction Manual page 33

ï Optional AT-180
The AT-180 automatic antenna tuner automatically
matches the IC-718 to the antenna. Once the tuner
matches the antenna, the tuning settings are memo-
rized as a preset point for each frequency range (100
kHz steps). Therefore, when you change the frequency
range, the tuning circuits are automatically set to the
memorized point.
CAUTION:
NEVER transmit with the tuner ON
when no antenna is connected. This will damage
both the transceiver and the antenna tuner.
DO NOT!
connect the AT-180 and AH-4 or AH-740
at the same time. Both tuners will not be function cor-
rectly.
TUNER OPERATION
• Tuner type setting (p. 46)
q Hold down [PWR] for 1 second to turn power OFF.
w While pushing and holding [SET], push [PWR] to
turn power ON.
e Push [UP Y] or [Z DN] one or more times to se-
lect [TUNER].
r Rotate the main dial to select "18."
• AT-180
AUTOMATIC ANTENNA TUNER
NOTE: NEVER select "4" (AH-4
), otherwise the transceiver automat-
TENNA TUNER
ically transmits when you turn ON the power. Push
[TUNER] to cancel the unexpected transmission.
Then, reselect the correct tuner type.
y Hold down [PWR] for 1 second to turn power OFF.
u Push [PWR] to turn power ON again.
• AUTO TUNE:
Push [TUNER] to turn the tuner ON. The antenna is
tuned automatically during transmission when the an-
tenna SWR is higher than 1.5:1.
• When the tuner is OFF, "
Tuning indicator;
AUTOMATIC ANTENNA TUNER
is selected.
AUTOMATIC AN-
" goes out.
Y
[TUNER]
RECEIVE AND TRANSMIT
operation
• MANUAL TUNING
During SSB operation at low voice levels, the AT-180
may not tune correctly. In such cases, manual tun-
ing is helpful.
Hold down [TUNER] for 1 second to start manual tun-
ing.
• CW mode is selected, a side tone is emitted, and
" " blinks; then, the previous mode is selected.
Hold down 1 second to start manual tuning.
If the tuner cannot reduce the SWR to less than 1.5:1
after 20 seconds of tuning,
case, check:
• the antenna connection and feedline
• the antenna SWR (p. 27: Meter function)
• Through inhibit
The AT-180 has a through inhibit mode. When select-
ing this mode, you can use the tuner at poor SWR's.
In this case, automatic tuning in the HF bands acti-
vates only when exceeding an SWR of 3:1. There-
fore, manual tuning is necessary each time you
change the frequency. Although termed "through in-
hibit," the signal will pass "through" the tuner if the
SWR is higher than 3:1 after tuning.
CONVENIENT
• Tuner sensitive condition
If you require critical tuning at any time during trans-
mission, select the tuner sensitive condition. See
page 51 for selection.
• Automatic tuner start
If you want to turn OFF the tuner when the VSWR is
1.5:1 or less, use "automatic tuner on" and turn the
tuner OFF. See page 46 for turning the function ON
or OFF.
5
Y
[TUNER]
goes out. In this
" "
29