IC-746 FAQ
AT-180
The AT-180 is intended for use in the shack with near-resonant antennas; it will tune a
maximum excursion of 3:1. The AT-180 was designed for the ham bands only but should
have sufficient band overlap to accommodate the MARS frequencies.
Here are the AT-180 specifications:
http://www.icomamerica.com/amateur/hf/at-180.html
No real point to using this ATU over the built-in one
AH-4
The AH-4 is an automatic antenna coupler, intended to tune random-length wire and whip
antennas. The AH-4 is mounted at the antenna, and the RF lead from the coupler to the
radiator should be as short as possible. The AH-4 covers 3.5 to 54 MHz (continuous) with a
7m (23 ft) wire antenna.
Here is the AH-4 brochure:
http://www.icomamerica.com/support/documents/brochures/ah-4.pdf
And a very informative site on the AH-4 (including an AH-4 FAQ):
http://www.hamoperator.com/ah4/ah4.htm
AH-3
The AH-3 is an older (out of production) alternative to the AH-4; it covers 1.8 to 30 MHz
(continuous) with a 7m wire antenna. There is info on it at the following WWW site:
http://www.qsl.net/n4pl/ah3/
AH-2
Older still, the AH-2 could cover 1.8 to 30 MHz with a 12m antenna or 3.8 to 30 MHz with a
3m antenna.
3.2.14 Can the TUNER button activate an external automatic ATU?
Yes. The IC-746 has a connector designed to directly connect to the Icom AH-4 automatic
antenna tuning unit. Page 80 in the instruction manual describes hookup and operation.
Once installed, pressing the TUNER button for 2 seconds will cause the rig to transmit 10w
in CW mode until the AH-4 finishes.
The IC-746 assumes that the AH-4 is connected to ANT-1 and automatic tuning will only
work there. ANT-2 is still available, but with no ATU.
In fact, there's a whole WWW site devoted to the AH-4. Check it out at:
http://www.hamoperator.com/ah4/ah4.htm
Most Icom tuners use the same interface (AH-2, AH-3, AT-180, etc...).
Page 33 of 113
2003-02-08
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