Icom IC-718 Instruction Manual - Page 30

5 RECEIVE AND TRANSMIT ï Optional AT-180 AUTOMATIC ANTENNA TUNER operation Y Y The AT-180 automatic antenna tuner matches the IC718 to the connected antenna automatically. Once the tuner matches an antenna, the variable capacitor angles are memorized as a preset point for each frequency 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 be damage both the transceiver and the antenna tuner. DO NOT! connect the AT-180 and AH-4 at the same time. Both turners will not be function correctly. TUNER OPERATION • Tuner type setting (p.46) q Push [PWR] for 1 sec. 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 select [TUNER]. r Rotate the main dial to select "18". • AT-180 AUTOMATIC ANTENNA TUNER is selected. NOTE: NEVER select "4" (AH-4 AUTOMATIC ANTENNA TUNER), otherwise the transceiver transmits automatically when turning the power ON. Push [TUNER] to cancel unexpected tramsmission. Then, re-select the tuner type correctly. y Push [PWR] for 1 sec. 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, " " goes out. • MANUAL TUNING During SSB operation on HF bands at low voice levels, 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 tun- ing. •CW mode is selected, a side tone is emitted, and " " blinks; then, the previous mode is selected. Y [TUNER] Push and hold 1 sec. to start manual tuning. If the tuner cannot reduce the SWR to less than 1.5:1 after 20 sec. of tuning, " " goes out. In this case, check the following: • the antenna connection and feedline • the antenna SWR (p. 26; meter function) • Through inhibit 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 higher than 3:1 after tuning. CONVENIENT • Tuner sensitive condition If you require critical tuning at any time during transmission, select the tuner sensitive condition. See p. 51 for selection. Y [TUNER] • Automatic tuner start If 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. Tuning indicator; 28