Icom IC-706 MKII Instruction Manual page 29

RECEIVE AND TRANSMIT 4
© Optional AT-180 AUTOMATIC ANTENNA TUNER Operation
The AT-180 automatic antenna tuner matches the IC-
7O6MKIl to the connected antenna automatically. Once
the tuner matches an antenna, the variable capacitor
angles are memorized as a preset point for each fre-
quency range (100 kHz steps). Therefore, when you
change the frequency range, the variable capacitors
are automatically preset 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.
Note:
«The AT-180 cannot be used for the 144 MHz band.
¢When operating on the 144 MHz band, pushing the
tuner switch selects the call channel (p. 33).
e The AT-180 can match both HF and 50 MHz bands.
However, operation is different for the HF and 50
MHz bands.
TUNER OPERATION
¢For the HF band:
Push [TUNER] to turn the tuner ON. The antenna is
tuned automatically during transmission when the
antenna SWR is higher than 1.5:1.
[TUNER/CALL]
Lights to indicate the AT-180
is turned ON.
¢When the tuner is OFF, the [TUNER] light goes out.
¢For the 50 MHz band:
Push and hold [TUNER] to tune the antenna. If the
[TUNER] light flashes slowly while transmitting, push
and hold [TUNER] again to re-tune the antenna.
[TUNER/CALL]
Flashes to indicate re-tuning
is necessary.
MANUAL TUNING
During SSB operation on HF bands at low voice lev-
els, the AT-180 may not be tuned correctly. In such
cases, manual tuning is helpful.
Push and hold [TUNER] for 1 sec. to start manual
tuning.
*CW mode is selected, a side tone is emitted, and the
[TUNER] light flashes; then, the previous mode is select-
ed.
[TUNER/CALL]
Push and hold for 1 sec. to start
manual tuning.
If the tuner cannot reduce the SWR to less than 1.5:1
after 20 sec. of tuning, the [TUNER] light goes out. In
this case, check the following:
ethe antenna connection and feedline
ethe antenna SWR (p. 25; meter function)
Through inhibit (HF bands only)
The AT-180 has a through inhibit condition. When
selecting this condition, the tuner can be used at poor
SWR's. In this case, automatic tuning in the HF
bands activates only when exceeding SWR 3:1.
Therefore, manual tuning is necessary each time you
change the frequency. Although termed "through
inhibit," the tuner will be "through" if the SWR is high-
er than 3:1 after tuning.
CONVENIENT
e Tuner sensitive condition (HF bands only)
If you require critical tuning at any time during trans-
mission, select the tuner sensitive condition. See
p. 55 for selection.
e Automatic tuner start (HF bands only)
lf you want to turn OFF the tuner under conditions of
VSWR 1.5:1 or less, use "automatic tuner on" and
turn the tuner OFF. See p. 46 for turning the function
ON and OFF.
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