Radials for ground-mounted vertical: insulated or bare?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K5DH, Jun 29, 2020.

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  1. K5DH

    K5DH Ham Member QRZ Page

    I am planning to install a Butternut HF-9V vertical in my back yard. I have a 500 ft. spool of #14 THHN that I plan to make my radials from. I've heard and read various arguments for and against insulated or bare wire for radials. I'd like to use the insulated wire I have, but if it will make an appreciable difference, I'm not against buying a spool of bare wire. Anyone care to offer an opinion on insulated v. bare radial wire?
     
  2. N3ZP

    N3ZP Premium Subscriber QRZ Page

    I have a vertical with about 60 radials. I started with bare wire since I had a spool of 16 ga bare copper. As I added radials I switched to #14 THHN and also bought the insulated radial wire from DX Engineering. The bare wire is brittle and also more likely to corrode in the lawn from chemicals already in the soil and lawn fertilizer. I don't think there is any advantage with bare wire, It's not really about contact with the soil. The nice thing about the DXE wire is that it's very "limp" and doesn't try to coil up. I used the U-shaped wire lawn landscape stakes from Home Depot to hold down the wire every 5 feet or so. I have also made them from wire coat hangers. DXE also sells stakes including plastic ones that biodegrade over time. They do break easily though . After a few weeks the wire disappears into the grass thatch. Use the wire you have. Good luck with your vertical

    Phil N3ZP
     
  3. W4EAE

    W4EAE Premium Subscriber QRZ Page

    Insulated wire is easier to work with and could conceivably last longer. Earth ground isn't really part of the the discussion as to radiation efficiency, but counterpoise is.
     
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  4. KK4NSF

    KK4NSF Ham Member QRZ Page

    I've used all sorts of wires for radials, and I don't see much of a difference between insulated and non-insulated as far as performance goes. Insulated does seem to last longer though.

    My personal preference is to use whatever is cheapest. You can sometimes find big spools of wire at hamfests at really low prices.
     
  5. WA4SIX

    WA4SIX Ham Member QRZ Page

    Whatever metal you can connect to the antenna will do just fine.
    I have used vinyl coated steel rabbit fencing that performed great

    Ed
     
    N4FZ likes this.
  6. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

    N1VAU likes this.
  7. AJ5J

    AJ5J Ham Member QRZ Page

    I know this does not apply to your ground-mounted vertical at all but I must mention one scenario where bare or insulated radials will make a very minor logistical difference: elevated radials (generally tuned).

    Because of the velocity factor, insulated radials will be 3 to 5% shorter than their bare counterparts. Perhaps not any sort of big deal in most installations---but if space for tuned radials is tight---every little savings in wire length will help (particularly for the low bands).

    73,

    Jeff
     
    K3RW likes this.
  8. N8AFT

    N8AFT Ham Member QRZ Page

    I have both.
    On ground radials are not tuned thus need not be ny certain or any accurate lengths.
    Mine are assorted length from 20 to 50 ft long. Stapled to sod. A few added every year.
    See the Handbook.
     
  9. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    For RF effects, measurements by N6LF showed that insulation makes little difference except for less than 8 radials, but even then it's not very large. Besides one should have considerably more than 8 buried radials. Personally, I used THHN stranded 14 gauge wire from the local box store for my vertical radials because it was readily available at reasonable cost. It was also much easier to work with than the bare solid wire.

    There should be some advantage to bare wire for for dissipating lightning energy into the ground. However, a ground rod should be installed at the radial plate anyway (and at the coax entry to the shack with surge protectors). I'm not sure how much practical advantage over insulated wire there would be, considering that the system isn't designed for a direct strike in any case. Another issue is the contact resistance of the wire to ground. At my station the first few inches of soil are usually bone dry in the summer which isn't very conducive to low resistance.

    A simple calculation: Voltage breakdown of typical PVC wire insulation varies but is probably 5 to 10 kV volts. Suppose the ground rod is 25 ohms to "real ground". A small lightning stroke current might be 10 kA, so multiply by 25 ohms to get 25 kV, and the wire insulation is going to break down and conduct current.

    If anyone reading this has measured numbers to show a practical advantage for bare wire please share it.
     
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  10. KA3CNC

    KA3CNC XML Subscriber QRZ Page

    I use insulated wire...I think its easier to work with....Don't forget to check out yard sales for wire to ....sometime you might hit the jackpot like I did....just purchased last week many rolls of #14 es #12 insulated wire..about 1000 feet total...the guy wanted $3 dollars for it....lol....he just wanted to get rid of it!!...as far as lawn staples check out lowes and home depot too....good luck
     

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