D If The Tuner Cannot Tune The Antenna - Icom IC-7800 Instruction Manual

10
ANTENNA TUNER OPERATION
■ Antenna tuner operation (continued)
• PTT TUNER START
• Antenna tuner of the IC-PW1

D If the tuner cannot tune the antenna

The tuner is always tuned when the PTT is pushed
after the frequency is changed (more than 1% from
last-tuned frequency). This function removes the "hold
down [TUNER]" operation and activates for the first
transmission on a new frequency.
This function is turned ON in set mode. (p. 12-16).
When using an external antenna tuner such as the
IC-PW1's tuner, tune with the external antenna tuner,
and turn OFF the IC-7800's tuner. After tuning is com-
pleted, turn the internal tuner ON. Otherwise, both tun-
ers tune simultaneously and correct tuning may not be
obtained.
See the instruction manual included with each antenna
tuner for their respective operations.
Check the following and try again:
• the [ANT] connector selection.
• the antenna connection and feedline.
• the untuned antenna SWR.
than 2.5:1 for 50 MHz band)
• the transmit power.
• 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 re-tune the antenna.
• 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 be tuned at the edge
of their bandwidth, therefore, tune such an antenna as fol-
lows:
[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.
10-6
(Less than 3:1 for HF bands; Less
(8 W for HF bands; 15 W for 50 MHz band)