Long Metal Fence as Counterpoise?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KW4TI, Nov 22, 2020.

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  1. KW4TI

    KW4TI Ham Member QRZ Page

    Ok, I am in a place where I can't really bury radials. However, the property does have a long chainlink fence enclosing the yard.

    I was thinking the antenna would be a "long wire" antenna (as long as I can get it) that would be in the trees above the yard above the chainlink fence, with the feedpoint being a few feet off the ground clipped to the chain link fence. That way the current is flowing (hopefully) mostly being the large metallic fence and the wire sticking out above it.

    Does this sound like it might work as a makeshift antenna using the chain link fence advantageously?
     
    VA3TFC likes this.
  2. KI4ZUQ

    KI4ZUQ Ham Member QRZ Page

    That is about what I have cobbled up in my backyard!
     
    VA3TFC likes this.
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

    At the risk of being accused of being a shill for a commercial maker of antennas, you could do worse than a coax-fed, 75m to 10m multi-band horizontal wire antenna that does not need a counterpoise like this one, (but works better with an added CM choke).

    If I was doing it, I would home-build that antenna for a parts cost of less than 25% of the finished product.

    If you can get it horizontal, more than 30ft high, it will work very well.
     
  4. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    Sure...why not?
     
  5. N3PM

    N3PM Ham Member QRZ Page

    The chances of all the metal parts in a chain link fence be connected are slim. Even less than that if it's a colored one.
    Mike N3PM
     
  6. KC3PBI

    KC3PBI XML Subscriber QRZ Page

    It might even work! Try it and tell us!
     
  7. W4HWD

    W4HWD Platinum Subscriber Platinum Subscriber QRZ Page

    The "ideal" counterpoise covers a surface area, not a perimeter. It may work as "makeshift" but not much more.
     
  8. KW4TI

    KW4TI Ham Member QRZ Page

    One thing I am wondering about this arrangement is if the resonant frequencies of the antenna are mostly determined by the length of the radiating wire and if the effective impedance of the ground "chainlink fence" is much less. The reason I am thinking that the chainlink fence might work better than expected is that the effective capacitance of a large metal plate (galvanized fence panels) might be fairly high and therefore able to store a lot of charge. This could be especially helpful if a 9:1 unun is used so that the current in the radiating element is three times that of the counterpoise/fence. Using an antenna analyzer to sweep the impedance of a long wire antenna would help figure this out. Perhaps you have a SWR sweep you could share?

    To answer the question of whether or not the parts of the fence are connected, I can use both a resistance tester as well as capacitance, as even if the panels are not connected together tightly, the gaps between them might be small (because of the tension in the chain link wires) so the RF can still pass along the fence. Being galvanized steel, the zinc oxide coating on the steel may become thicker over time due to weathering and progressive anodization, but still may be thin enough so that the capacitance between the wires is high.

     
  9. NN4RH

    NN4RH Premium Subscriber QRZ Page

    Just try it and see how it works.

    This question comes up a couple times a year and we usually end up having a multipage thread over-intellectualizing things, and then never hear back on the result.
     
    VE4AJM and KC3PBI like this.
  10. N1IPU

    N1IPU Premium Subscriber QRZ Page

    If you can place a vertical on the ground you can bury galvy wire fence there underneath it or stake it down and let the grass grow over it. I place a 20x20 grid and ground it with ground rods. Make sure to silver solder the connections between the fencing in several places where they meet. You can connect them mechanically but its unreliable over time. Works like a charm. You will find that chain link fence around the perimeter is pointless as a counterpoise.
     

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