Phasing a Half Square

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W5DXP, Apr 6, 2019.

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  1. W5DXP

    W5DXP Ham Member QRZ Page

    The half-square antenna is a broadside array. If the phase of the current in the second vertical element could be changed by 90 degrees, it would become an end-fire array. Has anybody ever turned a half-square into an end-fire array?
     
  2. KD8WU

    KD8WU Ham Member QRZ Page

    I guess not.
     
  3. KK9W

    KK9W Ham Member QRZ Page

    My question is how would you accomplish it? I have been looking at half squares recently.
     
  4. K1LH

    K1LH Ham Member QRZ Page

    End fire from two verticals spaced 1/2 wave apart requires a phase shift of 180 degrees per the ARRL book.

    I don't think its possible in practice with a half square, but in a few places I've seen it suggested you can put a 1/4 wave stub in the center of the horizontal wire to effect a 180 degree phase shift.

    Modeling this in EZNEC you do indeed get a 180 degree phase shift between the vertical sections with a 1/4 wave stub in the center of the horizontal wire - confirmed by looking at the currents tab. However the radiation pattern is almost omni-directional, and its no longer a low angle DX antenna, more a cloud warmer. I think what's happening is the radiation in the top horizontal wire is no longer cancelling and its radiating.

    Only spent a few minutes looking at this, someone else might be-able to offer more, or correct what I think is happening :)
     
  5. W5VQ

    W5VQ Premium Subscriber QRZ Page

    I used a half square on 40 meters with the 1/4 wave stub about 35 years ago and it seemed to work OK. I had a switch at the bottom of the stub to open or close it and change the pattern. Seems like I saw this in a 73 magazine article back in the late 70's.
     
    KK9W likes this.
  6. KK9W

    KK9W Ham Member QRZ Page

    Thank you for the info. That will give me something to search for while in the shack this weekend.
     
  7. K1LH

    K1LH Ham Member QRZ Page

    I did find this:

    [​IMG]

    Image from https://www.qsl.net/va3iul/Antenna/Wire Antennas for Ham Radio/Wire_antennas_for_ham_radio.htm
    132 - Double Bobtail Antenna for 20m

    Setting #1, three verticals spaced 1/4 wave apart - this is not a Bobtail Curtain, these are Half Square with an extra segment, the spacing between the vertical elements is still 1/2 wavelength except with 3 verticals making the top wire 1 wavelength long. Having three in a row compresses the lobe more, narrowing the beamwidth further which increases the gain. The Bobtail needs to be fed via the center vertical at the top (direct coax connection) or bottom (voltage fed) otherwise the pattern becomes distorted because currents are no longer symmetrical.

    Setting #2, that's a Half Square with the 1/4 wave stub in the middle, but EZNEC doesn't agree with that.

    Setting #3, I think they're isolating the middle vertical all together, if that's the case EZNEC doesn't agree with the pattern shown, more a pair of kidneys or a 4 lobed pattern.

    If this does actually work as described/assumed then I'm missing something, and need to be enlightened :)
     
  8. K1LH

    K1LH Ham Member QRZ Page

    AK5B and KK9W like this.
  9. HOUND189

    HOUND189 QRZ Member

    I'm amazed.. but no. You see, this is a perfect question, and (love) like forums. But, for entertainment how do you get past 'the dipoles. Ok... I put a technical thread of similar character and low-gremlin (behold) I got no replies. thread- uW antenna diy ...etc. Anyhow besides being a an nuclear fusion forum alumni and past confidant from anything to lasers.. my humble bow'nsess from your might, forum. thnky
     
  10. HOUND189

    HOUND189 QRZ Member

    I love the square ...any btw. And definitely consider the phase and reflector setup.
    I have more...
     

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