I Antenna Tuner Operation - Icom IC-7400 Instruction Manual

9
ANTENNA TUNER OPERATION

I Antenna tuner operation

The internal automatic antenna tuner matches the
transceiver to the connected antenna automatically.
Once the tuner matches an antenna, the variable ca-
pacitor 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 damage
the transceiver. Be careful of the antenna selection.
D D TUNER OPERATION
➥ Push [TUNER] to turn the internal antenna tuner
ON. The antenna is tuned automatically when the
antenna SWR is higher than 1.5:1.
• When the tuner is ON, the "TUNE" indicator appears.
• MANUAL TUNING
During SSB operation at low voice levels, the internal
tuner may not be tuned correctly. In such cases, man-
ual tuning is helpful.
➥ Push [TUNER] for 1 sec., to start manual tuning.
• A side tone is emitted and "TUNE" indicator blinks while
tuning.
• If the tuner cannot reduce the SWR to less than 1.5:1
after 20 sec. of tuning, the [TUNER] switch indicator
goes out.
• AUTOMATIC TUNER START (HF bands only)
If you want to deactivate the tuner under conditions
of VSWR 1.5:1 or less, use the auto tuner start func-
tion and turn the tuner OFF. This function activates
the tuner automatically when the SWR exceeds 1.5:1.
This function is turned ON in set mode. (p. 83).
• PTT TUNER START
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
"push and hold [TUNER]" operation and activates for
the first transmission on a new frequency.
This function is turned ON in set mode. (p. 83).
• Antenna tuner of the IC-PW1
When using an external antenna tuner such as the
IC-PW1's tuner, tune with the external antenna tuner,
while the internal tuner is turned OFF. After tuning is
completed, turn the internal tuner ON. Otherwise,
both tuners tune simultaneously and correct tuning
may not be obtained.
See the instruction manual included with each an-
tenna tuner for their respective operations.
75
[TUNER]
NOTES:
• The internal antenna tuner can only tune the HF and
50 MHz bands— the 144 MHz band cannot be tuned.
• NEVER transmit without an antenna properly connected
to antenna port in use.
• When 2 antennas are connected, select the antenna to
be used with [ANT].
• If the SWR is higher than about 1.5:1 when tuning above
100 kHz on an antenna's preset point, push [TUNER] for
1 sec. to start manual tuning.
• The internal tuner may not be able to tune in AM mode. In
such cases, push [TUNER] for 1 sec. to manually tune.
D D If the tuner cannot tune the antenna
Check the following and try again:
• the [ANT] connector selection.
• the antenna connection and feedline.
• the unaltered antenna SWR.
Less than 2.5:1 for 50 MHz band)
• the transmit power.
(8 W for HF bands; 15 W for 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 re-tune the antenna.
• turn power OFF and ON.
• adjust the antenna cable length.
(This is effective for higher frequencies in some cases.)
• Some antennas, especially for low bands, have a nar-
row bandwidth. These antennas may not be tuned at the
edge of their bandwidth, therefore, tune such an an-
tenna 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 Push [TUNER] to turn the antenna tuner ON.
w Select CW mode.
e Turn OFF the break-in function. (p. 55)
r Push [TRANSMIT] to set to the transmit condition.
t Set 3.55 MHz and key down.
y Set 3.80 MHz and key down.
u Push [TRANSMIT] to return to the receive condition.
(Less than 3:1 for HF bands;