How Should I Wire my J-38 Key?

Discussion in 'General Technical Questions and Answers' started by KD2PPY, Aug 9, 2018.

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  1. KD2PPY

    KD2PPY Ham Member QRZ Page

    I got this J-38 key off of eBay a little while ago and would like to get on the air with it eventually. The radio I need to hook it to is a Yaesu FT-450D. I believe there is something missing with this key too. most others I see have a bar on the back with two other connections. Is it okay if it's not there? [​IMG]

    Any tips and help would be very much appreciated to get this piece of history back on the air!

    Joe Greco KD2PPY
  2. NN4RH

    NN4RH Premium Subscriber QRZ Page

    The two connection posts that are missing are not that important. You have what you need.

    See page 45 of your FT-450D manual.

    For a Yaesu radio, you'll need a stereo audio plug and some two conductor cable, or a stereo audio cable with plug already on it. The plug whichever size (1/4 or 1/8) is the right size for that radio.

    If you're making a cable, solder one wire of the cable to the "tip" of the plug and another wire (or the shield) to the "shield" or "common" of the plug.

    The "ring" part of the plug is used for paddles, not used for straight keys. It's important that it be a stereo connector, anyway, even though part of it is not used.

    If you're using a pre-made stereo cable, you need to figure out which wire goes to the "ring" part of the connector, and do not use that one. Easy if you have an ohmmeter. If not, trial and error works.

    The two wires (or one wire and shield) at the other end of the cable connect to the two posts on the back of the key.
    Last edited: Aug 10, 2018
    KD2PPY likes this.
  3. NN4RH

    NN4RH Premium Subscriber QRZ Page


    Not a J-38 but they're all just switches and all wired the same:

  4. KQ4MM

    KQ4MM XML Subscriber QRZ Page

    Just like this ....

    N3AB likes this.
  5. KD2PPY

    KD2PPY Ham Member QRZ Page

  6. KD2PPY

    KD2PPY Ham Member QRZ Page

    Definitely a help. This is also my first key, so all information is being soaked up like a sponge! Thanks, Joe.
  7. N2EY

    N2EY Premium Subscriber QRZ Page

    Two comments on that photo:

    1) The binding post nearest the camera in that photo goes to the contact under the key lever. The other end of the wire that connects to it should connect to the tip of the plug. The other binding post (farther away) goes to the frame, and should connect to the shell of the plug (the bigger part).

    2) The key is mounted to the base by the two flat-head screws through the frame. For a more stable mounting, remove the two flat-head screws, turn the base around 180 degrees (a half turn), line up the holes, and reinstall the two flat-head screws. This will put the part of the base labeled "J-38" at the back of the base rather than under the knob.

    73 es GL de Jim, N2EY
    N3AB likes this.
  8. KA0GKT

    KA0GKT Ham Member QRZ Page

  9. N3AB

    N3AB Subscriber QRZ Page


    Kudos for giving CW a try, and for using a "loved by many" J-38.

    John N3AB
  10. WA9UAA

    WA9UAA Ham Member QRZ Page

    Didn't see a thing about the shorting bar. It can be useful when tuning up, but might be in the way otherwise. I had been known to remove some of mine but try the key first with the shorting bar moved to the right and out of the contacts. These needed more caution with the screen voltage on the contacts of older tube transmitters. ;) hth

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