ad: ARR

Halfsquare antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by G5TM, Mar 21, 2019.

Tags:
ad: L-HROutlet
ad: l-rl
ad: Left-2
ad: K5AB-Elect-1
ad: L-MFJ
ad: MessiPaoloni-1
ad: Subscribe
  1. N3DT

    N3DT Ham Member QRZ Page

    Mike, that EZ file will not import into my 4NEC2, the free version. It may be too involved for my cheapo version (5.8.16)? I've imported other EZ files, but not this one. Thanks for trying, unless you have another suggestion. Actually, I'd like to compare the square to my fairly high dipole (80 & 40) with real ground. If it is good enough, I might want to try a 160 version where I have no antenna. I've got the space and probably the height.
     
  2. W5DXP

    W5DXP Ham Member QRZ Page

    HalfSquare.png
     
  3. WR2E

    WR2E Ham Member QRZ Page

    Would dropping another vertical element from the center of the horizontal wire make this a 'bobtail'?

    Wonder what that would look like in the modeling?
     
  4. N3DT

    N3DT Ham Member QRZ Page

    I knew there was a reason I never built one. Here's a comparison of the half square to my 70' 40M dipole. No comparison, even if it has low angle radiation, the gain just doesn't compare. This is over my ground, with better ground it may be different. So just remember when someone says, low angle radiation, it doesn't necessarily mean better. Hard to beat a horizontal.

    half sq vs dip.jpg
     
  5. W1VT

    W1VT Ham Member QRZ Page

    In my case, my dipoles are only 30 to 40 feet high, so a 40M half square over really good, wet agricultural soil does work as DX antenna. But, commercial growers can't afford the cost of the soil in my yard. Lots of compost or "black gold" and time release fertilizer.
     
    Last edited: Mar 24, 2019
  6. W1FBV

    W1FBV Ham Member QRZ Page

    N3DT - Does your modeling assume the half square is at ground level? My 40 meter half square is elevated approximately six feet. I can't compare it in practice to a dipole because I don't have room for a dipole, but it outperforms an elevated half wave vertical in its favored directions. In fact, I bet it would beat your dipole if I could get it 70 feet in the air. Height is always best, especially in a cluttered urban environment.
     
  7. W5DXP

    W5DXP Ham Member QRZ Page

    I've been looking at a 40m half square and realized that it is 1/2WL on 80m where it would be an OCF with a less than terrible SWR.

    I may be wrong, but it seems to me that physics will not allow any common mode current to flow on the outside braid of the coax inside the aluminum tubing so no choke needed at the feedpoint.

    Hard to beat a 40m dipole at 70 ft. But is it hard to beat a 40m dipole at 40 ft? A 40m half square at 40 ft will beat a 40m dipole at 40 ft at all angles below 23 degrees, by 5dB at 10 degrees and 7dB at 5 degrees (by approximately one S-unit).
     
    Last edited: Mar 24, 2019
  8. WB2UAQ

    WB2UAQ Ham Member QRZ Page

    Just something to consider when using 77 material. While testing a transformer based on and FT-240-77 core I found that it went thru SRF at just under 1 MHz with about 6 or 8 turns applied (tested as a simple inductor). This means that for a choke, choking impedance (now capacitive) is already heading down hill so at 160 meters it won't offer much for limiting RF current. The transformer was intended for use with an EFHW for 160 so it was a bust. I found that an EFHW 1:54 transformer using a 3 turn primary and 22 turn secondary on an FT240-43 worked well with about 900 pF across its input using a test load of 2700 ohms (resistor). The insertion loss was not bad at all. 73
     
  9. N3DT

    N3DT Ham Member QRZ Page

    That half square I modeled was only a few feet above the ground at the bottom. I haven't looked at what it would do at 70' at the top, but then that would not be as easy as a dipole to implement and why bother? Notice I did say that if there's good ground and no available height for a decent horizontal antenna, things will change. If you put that half square over a salt water swamp, it would probably be better than my dipole. I'm just saying that in lots of circumstances a vertical antenna is not a better choice for those of us who have some high supports for a horizontal. But verticals are perfect for some, just not me and believe me I've tried lots. I guess I've been burned too much by vertical promises. We do what we have to.

    There's a lot of information out there that verticals have low angle radiation and that's the end of the conversation. Well, yes, they do, but how much? It's circumstantial and there may be better options.
     
  10. SM0GLD

    SM0GLD Ham Member QRZ Page

    It acts as a sleeve balun.
    https://www.w8ji.com/sleeve_baluns.htm
     

Share This Page