Old MFJ Keyer Jumper Questions

Discussion in 'Straight Keys - CW Enthusiasts' started by W3MAT, Oct 27, 2021.

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  1. W3MAT

    W3MAT Ham Member QRZ Page

    Hey there. Late starter here. Getting set up to learn the code.

    A couple of you guys are going to know right off the answers to the following, and I write asking your help.

    I’m juggling a bunch of things. ;)

    Question One

    What plugs and wire do you like to jumper a MFJ 408 keyer (see picture below) to Kenwood TS-830.

    Where do you like to source and can you supply a product link.

    I was thinking of making the jumper but if premade is inexpensive and convenient -- and you personally would go premade -- please advise.

    I’m guessing 3.5mm mono and ¼-inch (6.35mm) mono.

    Question Two

    What plug and wire from iambic paddles to keyer. I am guessing ¼-inch (6.35mm) stereo.

    For wire some kind of three-strand big box store bulk eh.

    Question Three

    So far I cannot find owners or service manual for MFJ Model 408 Deluxe Keyer II. I’m supposing close to others similar models. What other manual would suffice. Do you have a copy or link.

    Side Note

    I am definitely planning on straight key first; have QRP guys training oscillator coming. Am one week into listening watching G4FON first 10 characters. Waiting to hear back from Long Island CW Club on application.

    MFJ 408 Keyer Rear.jpg

    MFJ 408 Keyer Front.jpg
  2. KS2G

    KS2G Premium Subscriber QRZ Page

  3. W3MAT

    W3MAT Ham Member QRZ Page

    Nice!!! Thank you!!!
  4. N2UHC

    N2UHC Ham Member QRZ Page

    Honestly it looks like the output of your keyer is an RCA jack, so you'd want a cable with an RCA plug on one end, and I'm assuming a 1/4" phone plug on the other to the key jack of the radio. At least that's what my Kenwood TS-140 takes.

    Secondly, just looking at the picture it looks like the jack labeled "key" is where you plug in your paddles. That looks like a 1/4" phone jack, and you'd want a stereo plug. For wire I've long used the cords from computer mice, they have 5 conductors and are usually shielded. Since wired mice are starting to go away forever, you can use USB cords if you have one with a broken plug or something. I believe they are 4-conductor cords. The usual standard for wiring a plug onto a CW paddle cord is the tip is used for dits, the ring for dahs, and the sleeve for common, but I'm not sure what the MFJ keyer takes. When I started out, I had all my paddles wired up backwards because the Ramsey keyer I built had a backwards scheme. I did a modification to the PC board with a couple of pieces of wire and switched it around, and then switched the plugs on all my paddles around.
  5. W3MAT

    W3MAT Ham Member QRZ Page

    Now that you mention it, those DO look like RCA jacks. The unit is not here yet to confirm. Good eye. Thanks! Good recycling ideas on wire. Never thought of that. I like it. Thanks for note on typical plug-for-paddle, cord wiring. The story on the Ramsey keyer -- backwards, inputs wiring scheme -- is helpful to know, too.
  6. N2UHC

    N2UHC Ham Member QRZ Page

    I first realized the Ramsey keyer had a backwards scheme when I tried using my paddle with a friend's keyer. I didn't know any different, and that's when I learned that the typical configuration is to use the tip for dits, ring for dahs.

    But yeah, find an old wired computer mouse, either with the PS/2 plug or a USB mouse, and they work well for paddle cords. I think I may have also used old 4-wire telephone cord in the past, too, but it's solid wire and prone to breaking more than the stranded wire.

    For the output from the keyer to the radio, just find an old audio cable with RCA plugs on each end. Cut one off and solder a mono 1/4" phone plug to it.
  7. W3MAT

    W3MAT Ham Member QRZ Page

    I will actually do just as you say. Not only good function but efficient recycle. The Ramsey experience is a good story. Funny.
  8. VE3HIX

    VE3HIX Ham Member QRZ Page

    And don't forget that the 830 is a hybrid transceiver. You want to use the Grid Block connector on the MFJ keyer, not the Direct connector.

    Cheers and good luck,
    Bob VE3HIX
  9. N2UHC

    N2UHC Ham Member QRZ Page

    Good catch. I didn't realize the 830 has tubes.
  10. W3MAT

    W3MAT Ham Member QRZ Page

    Looking forward to seeing how that grid blocker circuit works. Key output on the transceiver I hear is at -65V. First and only HF rig so far for me. Love it. Have an Icom 765 on reserve though for backup.

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