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Thread: ADF antenna change

  1. #1

    ADF antenna change

    I now have the old post forward top center of the fuselage where the
    ADF antenna wire runs back to the tail just below the rotating beacon.
    Does someone have info about another spade-type antenna available and
    where it would be mounted. Could one be simply attached at the point
    where the old post is now?
    I'd like to leave that old wire setup far behind! (Actually I did
    leave part of it somewhere on a ramp in Gulf Shores AL!!)

  2. #2

    ADF antenna change

    David, it is not clear to me if you want another antenna to work with your present ADF, or an antenna to work with something else. ADF antennas are two types and the type that you use depends on the ADF. Some ADFs use a direction antenna on the belly of the airplane and a wire sense antenna (the wire that you lost). If your ADF is the old type with the sense antenna, you need to replace the one that you lost. If your ADF is a newer type (probably not very new?) the sense antenna is wound on a ferrite core and located in the direction package on the belly. Your antenna must match the design of the receiver to work well and they come as a package. Of course, many are replacing the ADF with a certified GPS and you can put the GPS antenna over the hole if you do.

    I hope that I understood the question.


  3. #3
    What type of ADF do you have. I have a King KR86 with single antenna on the belly. In fact I have 2 units and 2 antennas and an extra cable for the antenna. I also have the install manual for the ADF and it appears that you can have either type of antenna depending on how you wire it. I am about to remove the ADF from the plane since i have a GNS430 and want to drop the weight. Let me know if you have the same type ADF and I think i can help you out.

  4. #4

    ADF antenna change

    David, the ADF tunes the low frequencies of the AM broadcast band and below. These frequencies require long wire antennas. A lot of small wire wound on a ferrite rod will substitute for the long wire, but is very directional. The spade antennas are for the higher frequencies where the outer marker and DME work. The band where the Com radio and the Nav radio work at frequencies just above the FM broadcast band and require antennas about two feet long. Good, proper antennas are required for each of the radios and antenna design is a science and art in itself.

    David <> wrote:
    In, WILLIS COOKE wrote:
    > I hope that I understood the question.

    Yes you did Willis and thanks for the reply. I had no idea an ADF was
    so complicated... I guess I'll have to string another wire up there.
    (I have airplane cover issues that a wire antenna directly affects and
    wanted to lose the wire in favor of a spade or the like).

  5. #5
    I'm not sure that it came through well enough to date in this thread, though I think it is reflected in a few others. There are two types of ADF antenna set-ups. The older type, which most of us have or had, has the long sense wire above the fuselage and the 'pancake' loop antenna under the forward belly. As Mike D notes, there is another style of ADF antenna which does not use the long wire on the top. It instead uses a 'long wire' that is wrapped around a ferrite core, and which is actually housed inside the same shell that contains the loop antenna; the pancake antenna under the belly. Anyone old enough to recall the 9V early AM-FM 'transistor radios' has probably seen one of these ferrite core antennas.

    So the short story is that if you absolutely must keep your ADF for some reason, AND if (as Mike D indicates) your model of ADF can be set to use the ferrite core version, you can get by with just the pancake belly antenna (the type that contains both antennas). I'm not an 'Avionics Guy', so I cannot advise you any further on that aspect.

    If you need a replacement long wire, Aircraft Spruce used to sell a pretty low-priced kit containing a stainless-steel wire.

    Personally, I would not put a dime into an old ADF, unless you have a really, really good reason to keep it working. It will become a money pit if you try to keep it going. Most current avionics shop staff can no longer diagnose and repair them properly, in today's GPS world, so they will throw parts and labor at any problem.

  6. #6
    Some Canuck airspace..(still) requires adf ops (probably waay noth, in the boonies)

    Certainly, for an Atlantic crossing.

    Quote Originally Posted by Rellihan
    if you absolutely must keep your ADF for some reason

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