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59
9
INTERNAL ANTENNA TUNER
9-1 Before operating
9-2 Tuner operation
➀
Make sure that output power on the HF bands is
higher than 8 W; on the 50 MHz band, higher than
15 W.
➁
Push [TUNER] to turn the internal antenna tuner
ON. (See p. 3—
!5
RF POWER CONTROL.)
• The antenna is tuned automatically when the SWR is
higher than 1.5:1.
• When the tuner is ON, “TUNER” appears in the display.
[TUNER]
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 ca-
pacitors are automatically preset to the memorized
point. (See p. 62—19 Auto tune.)
■
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 2 sec. to start manual tuning.
• During manual tuning, “TUNE” flashes.
• If the tuner cannot reduce the SWR to less than 1.5:1
after 20 sec. of tuning, [TUNE] disappears and “through”
is selected.
■
IF THE TUNER CANNOT TUNE THE
ANTENNA
• Check the unaltered antenna SWR (less than 3:1 for
HF bands; less than 2.5:1 for 50 MHz band).
• Repeat manual tuning several times.
• Tune with a 50
Ω
dummy load and re-tune the an-
tenna.
• 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 band width. These antennas may not be tuned 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.
➀
Push [TUNER] to turn the antenna tuner ON.
➁
Select CW mode.
➂
Turn OFF the break-in function (p. 44).
➃
Push [TRANSMIT] to set the transmit condition.
➄
Set 3.55 MHz and key down.
➅
Set 3.8 MHz and key up.
➆
Push [TRANSMIT] to return to the receive condition.
■
NOTES
• The internal antenna tuner can only tune the HF and
50 MHz bands—the 144 MHz band cannot be tuned.
• DO NOT transmit if no antenna is connected to
[ANT1] or [ANT2].
• 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 2 sec. to start manual tuning.
• The internal tuner may not be able to tune in AM
mode. In such cases, push [TUNER] for 2 sec. to
manually tune.
Summary of Contents for IC-746
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