If The Tuner Cannot Tune The Antenna - Icom IC-7851 Instruction Manual

13
ANTENNA TUNER OPERATION
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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
• Antenna tuner in the IC-PW1
When using an external antenna tuner such as the IC-
PW1's tuner, tune with the external antenna tuner, and
turn OFF the transceiver's tuner. 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 operation.
D If 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 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 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.
(p. 15-14).
(Less than 3:1 for the HF bands,
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