Icom IC-7610, Basic Manual

Page: 51 / 80

7
ANTENNA TUNER OPERATION
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7-3
About an external antenna tuner
The optional AH-4
antenna tuner
matches the
IC-7610 to a long wire antenna more than 7 m/23 ft
long (3.5 MHz and above).
In addition, using the optional AH-2b
antenna
element
matches the IC-7610 to a whip antenna more
than 2.5 m/8.2 ft long (7
~
50 MHz).
The optional AH-740
automatic tuning antenna
covers 2.5 to 30 MHz range with the whip antenna that
is supplied with the AH-740.
R DANGER HIGH VOLTAGE!
NEVER touch the antenna element while tuning or
transmitting. Always install it in a secure place.
NEVER operate the AH-4 or AH-740 without an antenna
connected. The tuner and transceiver will be damaged.
D
Using the AH-4 or AH-740
1. Turn ON the transceiver.
•“TUNE” is displayed.
L
Each time you push TUNER
,
the AH-4 or AH-740 is
turned ON (the indicator on the
TUNER
key lights) or
OFF (bypassed).
2. Hold down
TUNER
for 1 second to start manual
tuning.
• The tuner reduces the SWR to less than 2:1 after 2~3
seconds of tuning.
L
While tuning, a side tone is heard and the indicator on
the
TUNER
key blinks red.
L
If the tuner cannot reduce the SWR to less than 2:1
after 15 seconds of tuning, the indicator goes out.
3. After tuning, the indicator stops blinking and lights
white.
L
When the long wire antenna cannot be tuned, the
indicator goes out. In that case, the AH-4 is bypassed
and the wire is directly connected.
NOTE: When the wire antenna cannot be tuned, check the
wire length and connection.
Note that the AH-4 cannot tune a wire that is a ½λ long or
on a multiple of that frequency.
Using the Internal antenna tuner
1. Push
TUNER
to turn ON the internal antenna
tuner.
•The indicator on the
TUNER
key lights.
2. Tune the antenna.
L
To tune the antenna, see “Manual tuning” or “PTT
Tuner start” below.
D
Manual tuning
You can manually tune the antenna before
transmitting for the first time.
1. Hold down
TUNER
for 1 second to start manual
tuning.
• The tuning normally takes 2~3 seconds.
•The indicator on the
TUNER
key blinks red.
2. After tuning, the indicator on the
TUNER
key lights
white, and the internal antenna tuner stays ON.
L
If the tuner cannot tune, the indicator on the
TUNER
key goes out, and the tuning circuit is automatically
bypassed.
D
PTT Tuner start
The tuner is always activated when [PTT] is pushed
after the frequency is changed (more than 1% from
the last-tuned frequency). This function tunes the
antenna for the first transmission on a new frequency.
L
This function can be turned ON in the “PTT Start”
item on the TUNER screen.
(p. 8-3)
MENU
» SET > Function > Tuner > PTT Start
NOTE:
If the SWR is higher than about 1.5:1 when tuning more
than 100 kHz on an antenna’s preset point, hold down
TUNER
for 1 second to start manual tuning.
If the tuner cannot tune the antenna
•Repeat manual tuning several times.
• Even if the tuner cannot tune the antenna on the first
tuning, it may success at the second tuning.
• Some antennas, especially for the 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.
1. Set 3.55 MHz, and hold down
TUNER
for 1
second to start manual tuning.
2. Set 3.80 MHz, and hold down
TUNER
for 1
second to start manual tuning.