Icom IC-7850 Instruction Manual - Page 204

Previous view 13 ANTENNA TUNER OPERATION ■■Antenna tuner operation (Continued) • PTT TUNER START The tuner is always activated when PTT is pushed after the frequency is changed (more than 1% from last-tuned frequency). This function removes the "hold down [TUNER]," and activates the tuner for the first transmission on a new frequency. This function is turned ON in Set mode (p. 15-14). • Antenna tuner in the IC-PW1 When using an external antenna tuner such as the ICPW1's tuner, tune with the external antenna tuner, and turn OFF the transceiver's tuner. Otherwise, both tuners tune simultaneously and correct tuning may not be obtained. See the instruction manual included with each antenna tuner for their respective operation. DDIf the tuner cannot tune the antenna Check the following and try again: • the [ANT] 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/capacity If the tuner cannot reduce the SWR to less than 1.5:1 after checking the above, perform the following: • Repeat manual tuning several times. • Tune with a 50 Ω dummy load and then retune the anten- na. • Turn power OFF and ON. • Adjust the antenna feedline length (This is effective for higher frequencies in some cases.) • Some antennas, especially for low bands, have a narrow bandwidth. These antennas may not tune at the edge of their bandwidth, therefore, 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. q Set 3.55 MHz and hold down [TUNER] for 1 second to start manual tuning. w Set 3.80 MHz and hold down [TUNER] for 1 second to start manual tuning. 13-8