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AA7OL Niko Takahashi
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Icom AH-4 and AH-3 ( automatic antenna tuner ) connection to any radio

Both AH-3 and AH-4 are similar

Here is a redesign of connection digram of the ICOM IC-AH3 and IC-AH4 by 5B4AEZ.

There is four wire control cable coming out beside coax cable.

Control cable has

    White: Start tuning

    Green: Tuning in process

    RED: 12 V DC input

    Black: GND

Tuning Process

  1. Put about 10 watts of power into tuner. ( CW )

  2. After about 0.5 second, press start switch for a moment. ( use momentary contact switch )

  3. LED start blinking , which indicate tuning is in process.

  4. After about 3 seconds or so, LED shut off, and tuning is completed,

If tuning is successful SWR should be less than 1.2

Some radio start to reduce the power when SWR is high, this tuner takes at least 10 watts of power for tuner to work properly. Most of the 100 watts radio should not have any problem, since they still put out 10 watts or so, even with high SWR.

But, it does not work with some QRP radio ( 5 watts or less ).

Adjust power level, if necessary.

You may extend control cable to 100 feet , it still work fine, you can put this tuner on top of tower.

Let me know , how it worked

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31-01-2000 Icom, AH-4, AH-3 ( automatic antenna tuner ) connection to any radio..    (Selected article)
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