True balanced auto-tuner?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K5DH, Aug 14, 2017.

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  1. K5DH

    K5DH Ham Member QRZ Page

    Does anyone currently offer an auto-tuner for balanced feeders? I don't mean a coax matcher with a balun tacked onto the output. I mean the automated equivalent of the ol' Johnson Matchbox or a W1FB balanced tuner from the ARRL Handbook... the real thing that is designed for nothing but balanced feeders.
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    True, but it's not an auto-tuner, it's manual.
     
  3. W6OGC

    W6OGC Ham Member QRZ Page

    The Icom AH-4 doesn't use a balun.
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    It's also not balanced, it's a single-ended tuner by design.

    And it has a 150W power rating.
     
  5. W6OGC

    W6OGC Ham Member QRZ Page

    We use them in balanced apps without detriment.

    120 watts, actually, and is more than enough.
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    You certainly can use any single-ended tuner for balanced lines if you want to -- I've done it, also.

    But it's not a balanced tuner.

    A balanced tuner tunes both sides of the line differentially and forces the same current into both conductors, 180 degrees out of phase. Neither conductor is connected to ground or common to the same ground as the coax that feeds it.

    PALSTAR probably could make an auto-tune version of their balanced line tuner, but it appears they haven't done that. Might be a market for that, or maybe not -- I don't know.
     
  7. K8JD

    K8JD Ham Member QRZ Page

    Consider the MFJ974
    The rather inexpensive MFJ 974 is a true balanced tuner that doesn't rely on a BalUn. There is also a high power model, I believe, if you run more than 200 W.
    This tuner uses a twin T network, on each side of the antenna terminals, the tuning caps are mechanically linked to turn together.
    I got one, about 6 years ago, when I designed a 20M EDZ antenna. I used 450 Ohm balanced twinlead and found the antenna actually worked rather well from 5 to 18.1 MHz !
    It's a manual tuner but I made a chart for all the bands I use and can pre-tune it when I change bands. Then a few seconds of fine tuning gets me right to 1:1 SWR.
    I don't know why everyone HAS TO HAVE a computer do all the work ????
     
    K2CAJ likes this.
  8. N7ZDR

    N7ZDR Ham Member QRZ Page

  9. MIKESM

    MIKESM QRZ Member

    Yes, that is the only balanced autotuner I could find as well. But price is skyhigh... There is no reason for one to cost THAT much.

    thx
    mike
     
  10. N8CMQ

    N8CMQ Ham Member QRZ Page

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