icom ah-2

Discussion in 'General Technical Questions and Answers' started by KB2SDR, Jun 26, 2002.

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  1. KB2SDR

    KB2SDR Ham Member QRZ Page

    Hello everyone!

    I just received an Icom ah-2 from a friend of mine, that had gotten it when he purchased a marine rig from a friend. Unfortunately, it did not come with anything but the tuner module. I was wondering if there is a way to make an interface for it that will allow me to connect the rig to it. I am also less the manual and schematics for it. I have searched on the web and was unsuccessful finding one.

    Any info is appreciated.

  2. W9GB

    W9GB Ham Member QRZ Page

    An AH-2b is the 2.5 meter long antenna element (whip antenna) for mobile operation with the AH-4 tuner.

    The AH-4 is Icom's premier (HF and 6 meter) automatic antenna tuner.  Frequency coverage for the AH-4 is 7 to 54 MHz with the AH-2b whip antenna (3 - 54 MHz with a long wire).  A shielded control cable (Icom part # OPC-420) connects the AH-4 tuner to many Icom radios.  This cable provides the proper interface (voltage, ground, start and key) from the radio to the tuner.

    Your description sounds like you have both the AH-4 and the AH-2 ?

    The AH-4 manual is available on the Icom America web site: www.icomamerica.com

    Select:  Support --> Documents --> Scroll down to Options and Accessories (AH-4 is the first entry).  The file is in Adobe Acrobat "PDF" format

    If you still need a paper manual or tech support:

    ICOM America's Technical Support-by-Phone please call (425) 454-7619, Monday - Friday, 8:00 AM - 4:30 PM Pacific Time. (Please note: this free support-by-phone service is extremely popular. You may have to wait on hold during peak business hours.)

    ICOM America, Inc.
    2380-116th Ave NE
    Bellevue, WA 98004
    Phone: (425) 454-8155
    Fax: (425) 454-1509
    Customer Service: (425) 454-7619

    E-mail addresses:

  3. KB2SDR

    KB2SDR Ham Member QRZ Page


    Thanks for the reply, but it seems that you are jumping the gun. I am positive that I have an ic-ah2, i would like to know if the main unit is usable without the smaller unit or not. On the following link you will see  the ah2 with a small box next to it. I want to know if anyone knows what it is used for, and will the whole unit work without it. I had called Icom many months back to see if the box was still available, but I was told it is no longer carried. The person I received the unit from has misplace the manual. I am asking for help before I call icom for the manual and the schematics.


  4. W9GB

    W9GB Ham Member QRZ Page

    Jason -

    The photo did help, forgot about this model (popular with boaters using the IC-735)

    Here is an valuable web site you should bookmark:

    So you have the earlier model (IC AH-2).

    The "controller unit" (AH-2a) is 2.1" (W) x 2.5" (H) x 8.1" (D) in addition to the standard tuner (AH-2b).

    The AH-2 was designed for the IC-735 transceiver.

    Here is the hookup diagram for the Controller and Tuner Units with the IC-735 transceiver (note the controller unit):

    This controller (AH-2a) fits to the side of an ICOM 735 SSB/Ham radio and generates a signal that is used by the tuner (AH-2b) to auto tune the backstay.  The 735 does not have a built in signal generator like most of the other Icom transceiver models.  Bob Grove still has this controller box available (bargain bin) at:

    Later brochure for the Icom AH-2a model
    [Front page]
    [Back page]

    Additional links:

    --------------------------------[no warranty]------------------
    Double check with Icom technical support (or a schematic), BUT IF you use this unit with the Icom 706, and connect the control cable(4 pin molex connector), from the back of the AH-2 controller to the "like connector" on the rear of the IC-706. The 706 tuner button now becomes the control button for the AH-2 (or AH-3).

    The 4 conductor interface from the radio to the tuner is (voltage, ground, start and key).

    Use the AH-2 (or AH-3) as described in the IC-706 instruction manual.

    73 de w9gb
  5. KB2SDR

    KB2SDR Ham Member QRZ Page

    Thank you very much, you have been a big help. I was going to ask about the 706, but you beat me to the punch. I will have to order the tuner control for my other rigs. At 29.95, you can't beat that.

    Thanks again

  6. W9GB

    W9GB Ham Member QRZ Page

    Jason -

    Unless you will operate the AH-2 with an Icom IC-735 transceiver or desire to have the complete system (for future sale), you do not need the controller for other Icom transceivers.  [It was lucky that I saw Bob Grove had one of these controllers earlier this week.]
    You would have to check with Icom, if the controller allows other transceivers (e.g. Kenwood, Yaesu) to operate with this tuner.

    I already mentioned the IC-706 interconnection. My Icom 756Pro has the 4 connector Molex plug for connecting a AH-2, AH-3 or AH-4 automatic tuner at the bottom center of the back panel .

    Best wishes.

    73 de w9gb
  7. W9GB

    W9GB Ham Member QRZ Page

    I did find that K9EQ has built an AH-4 interface so that it can be used with other transceivers.  You may wish to look at this web page for more information.  The AH-2 was the earlier version of this current automatic tuner (AH-4).


    The AH-4 Interface

    Q: How does the AH-4 differ from the AH-3?

    A:  The wiring is identical and I assume that the AH-3 will work where ever the AH-4 will and visa versa. I did notice, however, that the 706 MKIIG implements some special circuitry just for the AH-3. It is not clear to me why this is done. The main difference from the user's point of view is that the AH-3 is specified to operate on 160 meters, while the AH-4 eliminates 160 and includes 6.

    73 de w9gb
  8. KB2SDR

    KB2SDR Ham Member QRZ Page

    Thanks for the feedback. I did call icom to see if the ah-2 is compatable with my icom 706 and 737a. They told me that there should be no problems that the pinout is the same for all the icom tuner units. I did try the unit with a 25 foot wire and it only seemed to tune 15m. I'll play with it a bit more to see if there is a problem or not.

  9. HB9US

    HB9US Ham Member QRZ Page

    AH-2 occasionally fails to tune 80 & 40m

    My AH-2 is connected to a 27m sloping wire. Since a while it fails to tune in the 80 & 40m bands. The tuner is mounted outside, on the roof of my house. I found that when the sun shines on the tuner and "warms" it up, it does tune on 80 and 40m.
    Does anybody know this problem?
    73 Werner HB9US
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