Icom IC-7410 Instruction Manual - Page 90

9 ANTENNA TUNER OPERATION ■ Antenna tuner operation The internal automatic antenna tuner automatically matches the transceiver to the selected antenna. After the tuner matches an antenna, the variable capacitor settings 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 setting. CAUTION: NEVER transmit with the tuner ON when no antenna is connected. This will damage the transceiver. Be careful of the antenna selection. 4 For your convenience When you purchase a brand-new antenna, or you want to change the antenna settings, you can erase all of the internal antenna tuner preset points with "Tuner Preset Clear" in the Set mode. (p. 87) D Tuner operation ➥ Push [TUNER] to turn ON the internal antenna tuner. The antenna is automatically tuned when the antenna SWR is higher than 1.5:1. • When the tuner is ON, " " appears. D Manual tuning If you transmit in SSB with a soft voice, the internal tuner may not automatically tune correctly. In such case, manual tuning is helpful. ➥ Hold down [TUNER] for 1 second to start manual tuning. • A sidetone sounds, " " blinks and the TX indicator lights red while tuning. • If the tuner cannot reduce the SWR to less than 1.5:1 within 20 seconds of tuning, " " disappears and the TX indicator goes out. NOTES: • NEVER transmit without an antenna properly con- nected to each antenna port in use. • When 2 antennas are connected, select the an- tenna to be used, by pushing [ANT•METER]. • If the SWR is higher than about 1.5:1 when tun- ing farther than 100 kHz from an antenna's programmed preset point, hold down [TUNER] for 1 second to start manual tuning. • The internal tuner may not be able to tune in the AM mode. In such case, hold down [TUNER] for 1 second to manually tune. [TUNER] ❍ If the tuner cannot tune the antenna, check the following and try again: • the correct antenna connector selection. • the antenna connection and feedline. • the untuned antenna SWR. (Less than 3:1 for the HF bands; Less than 2.5:1 for the 50 MHz band) • the transmit power. (8 W for the HF bands; 15 W for the 50 MHz band) • the power source voltage/current capacity. ❍ Tuning a narrow bandwidth antenna Some antennas, especially for the low bands, have a narrow bandwidth. These antennas may not be tuned beyond the edge of their operating bandwidth, therefore, manually tune such an antenna as follows: [Example]: Suppose you have an antenna which has an SWR of 1.5:1 at 3.55 MHz and an SWR of 3:1 at 3.8 MHz. If the tuner still cannot reduce the SWR to less than 1.5:1 after checking the above, perform the following: • try manual tuning one or more times. • adjust the antenna feedline length. (This is effective for higher frequencies in some cases.) q S elect 3.55 MHz and hold down [TUNER] for 1 second. to start manual tuning. w S elect 3.80 MHz and hold down [TUNER] for 1 second to start manual tuning. Even if manual tuning does not tune the antenna and the tuner turns OFF the first time, it may tune the antenna the second time. 83