Homebrew tuner

Discussion in 'Homebrew and Kit Projects' started by KF4ZGZ, Jul 14, 2017.

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  1. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    Something I have wanted to build for a long time.
    At a hamfest Saturday, I picked up the variable capacitor for 10 bucks.
    Sunday, the junkbox produced the rest of the parts and I kludged together a working unit using another coil that was a shunt coil for a mobile antenna. Even though the coil was small it worked on 20m and up.

    I then made the current coil and mounted everything permanently on the board.


    According to my MFJ-259B it will tune my 80m loop on all bands to 1.5 or better.

    Put it in line yesterday and I was told I had rf on my signal.

    I listened to myself on 80m using websdr this morning and it sounds more to me like an 60 cycle hum.

    Any ideas on where to look to solve this?

    I plan on sourcing a metal enclosure today to see if that helps.
    Another thought is to finalize all the connections by soldering .... which I plan on doing anyway.

  2. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    The metal enclosure should do the trick.
  3. N7EKU

    N7EKU Ham Member QRZ Page


    Probably you already checked, but is it (or the coax) near any line transformers (like from a linear power supply or non-switching wall wart kind)?


  4. G3YRO

    G3YRO Ham Member QRZ Page

    With the right values, an ATU should always be able to give you a perfect 1:1 match !

    What kind of circuit are you using?

    If you're using it to feed a Loop, is it a proper Balanced design?

    Roger G3YRO
  5. AA7EJ

    AA7EJ Ham Member QRZ Page

    Any ideas on where to look to solve this?
    Since the tuner is in "work in progress" state - how about temporary "enclosure" likes
    large cooking pot or turkey frying aluminum pan?
    Not sure how you getting 60Hz into "just" tuner, but...
    Can you post the schematic?
    73 Shirley

    PS One of the better "sources" for home-brew tuners is hardware from ARC5 WWII US transmitters - both capacitors and coils.
    You cannot beat the rugged mechanics, but most people just throw them away!
  6. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    The circuit is a basic L-network. My intent is to use it with 600-ohm feedline and a dipole.
    The loop just happens to be what I have up right now.
    The coil is 60-70 turns, and I have no idea what the variable is.

    Last edited: Jul 14, 2017
  7. N5DMC

    N5DMC Ham Member QRZ Page

    Looking good so far Matt, also.....A grounded enclosure is an active component of your matchbox, good luck.

    Last edited: Jul 17, 2017
  8. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    UPDATE: The tuner is actually fine!
    Apparently my IC-706 MKII is picking up ac line noise.

    Used the tuner (with newly completed popcorn tin enclosure) on 80m this morning and it is all FB.
    Can't wait to try it on a dipole.
    Now to figure out the 706 .........

  9. AA7EJ

    AA7EJ Ham Member QRZ Page

    Not sure how you getting 60Hz into "just" tuner, but...

    I guess the kid was right, at least this time.
    It may not be that easy to find the real source , but it would be better than just putting band aids (toroids) here and there.
    Patience is a virtue.
    Good luck.

    73 Shirley
  10. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    pic test ..... goodbye photobucket


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