Halfsquare antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by 2E0TWG, Mar 21, 2019.

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  1. AF7ON

    AF7ON Ham Member QRZ Page

    If you follow G3TXQ's suggestion, you can remove the vertical wire at the driven end and replace it by using the coax shield of the feed - you just relocate the balun down to the quarter wave point where the first vertical wire ended - mechanically much simpler.

    Mike
    AF7ON
     
  2. SM0GLD

    SM0GLD Ham Member QRZ Page

    I use one mix-77 and one mix-43 in series on the same piece of coax.
    For higher frequencies I use one mix-43 and one mix-61 if nessecary.
     
  3. W5DXP

    W5DXP Ham Member QRZ Page

    Back in 2010 when I first heard about G3TXQ's (SK) suggestion, I thought a sleeve over the coax would work better than just the coax braid. We could have a quarter-wavelength of aluminum tubing insulated from ground by a short non-conducting support. The coax could be routed up the inside of the tubing and the tubing becomes one of the two required supports.
     
    K2CAJ likes this.
  4. W5LZ

    W5LZ Ham Member QRZ Page

    Draw it. The verbal description makes no sense to me.
     
  5. K2CAJ

    K2CAJ XML Subscriber QRZ Page

    That would make more sense, because a choke at the top would be in a better position. A choke at the bottom would be at a high voltage point on the radiator---where it is expected to serve as an insulator between the 1/4λ of outer braid and the rest of the cable.
     
  6. N3DT

    N3DT Ham Member QRZ Page

    Mike (ARK), Could you be prompted to share the nec file? I'd like to play with it.
     
  7. WA7ARK

    WA7ARK Ham Member QRZ Page

    As soon as I get dressed, and walk over to the "lab"
     
  8. WA7ARK

    WA7ARK Ham Member QRZ Page

    Remove the .txt after saving it to your disk.
     

    Attached Files:

  9. N3DT

    N3DT Ham Member QRZ Page

    Tnx. Dave
     
  10. AF7ON

    AF7ON Ham Member QRZ Page

    Using a tubing element as a quarter-wave stub is perhaps a better alternative than just trying to choke the coax at the high-voltage point! Of course, you then have the high voltage at the bottom end of the tube to insulate from the coax shield where it exits the tube. However, properly done, this should eliminate most current on the coax shield and reduce the necessity for choking.

    Mike
    AF7ON
     

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