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please school me on radials

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KN4CQB, Jul 12, 2018 at 6:06 PM.

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  1. KN4CQB

    KN4CQB Ham Member QRZ Page

    i am currently using an OCF dipole at about 35 feet as my only antenna. For a second unit I
    Am thinking about a multi band vertical on some type of mast also in the trees behind my house or even better next to the house.

    Other than the fact that I need to run as many radials as possible I need some help on location. With the antenna on a mast is there typically some part of the system to attach the radials at ground level?

    I also have a dog that may be in the area. Will he be ok if the radicals are on the ground? I would think RF burns would be an issue.

    lastly for ease of installation I could mount the antenna from a bracket on the side of my house. This would then prohibit running 360 degree radials. Is this a big problem.

    Thanks ....73
     
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Radials must be connected at the vertical antenna's feedpoint, and commercially made verticals all have some method of doing this by design. As such, if you install the vertical "on a mast" above ground level, then the radials would also be "up at the base of the antenna," on the mast, starting at the same height as the antenna.

    If you bracket a mast to the house and install the vertical above the roof of the house, all the radials would be "up there," so you can likely use the roof to support radials for maybe 180 degrees (or more, if the house is L-shaped!) around the antenna. Radials in the "other direction" could be tied off to trees or other elevated supports. No problem with dogs, or kids, or burns...

    There are some HF vertical designs that don't require you to "add" any radials at all, as they have high-Z feedpoints (matched to 50 Ohms via transformers and stuff, part of the antenna) and can use reduced-sized radials pretty effectively. Those usually have 6-8-10-12 stainless steel "rod" elements that aren't long (often only about 4' long, in all directions) and come with the antenna, along with a way to attach them. Install one of those completely above the roof and it can work well.

    Examples:

    http://www.cushcraftamateur.com/Product.php?productid=R-8
    http://www.hy-gain.com/Product.php?productid=AV-640
    https://www.mfjenterprises.com/Product.php?productid=MFJ-1796

    Or an antenna that's designed like a center-fed vertical dipole, with built-in end loading on top and bottom:
    http://gapantenna.com/shop/antennas/titan-dx/

    ...lots more exist.
     
    AE1N likes this.
  3. NH7RO

    NH7RO Ham Member QRZ Page

    Keep your antenna away from house; no good can ever come from that arrangement.

    If you have dogs running around you'll need to insulate the ends of the radials.

    Elevated verticals perform better than ground mounted ones as a rule; with elevated Marconis you'll be able to run far fewer radials than if ground mounted.

    N6LF's findings reduced to a nutshell: 4 radials 0.15 to 0.40 lamda 4 feet above avg ground are the equivalent of 120 ground radials all else being the same.

    If elevated aim for 7-8' or more so humans/animals don't run into them.

    Search Rudy Severns, N6LF for the full story.
     
    AI3V and AE1N like this.
  4. EA1DDO

    EA1DDO Ham Member QRZ Page

    If you can, elevated radials are best option. No matter how much, but they use to be attached to the base of the antenna, I mean, elements will be at same height as antenna base.
    Minimum 2 radial per band, best result 4 radials.
    Try to make them 1/4 wavelength. Same size as a dipole for that frequency.
    Use good insulators at the terminations as high voltage is present.
     
    WZ7U and AE1N like this.
  5. KN4CQB

    KN4CQB Ham Member QRZ Page

    Good stuff guys! Keep it coming! Anyone want to contribute to my antenna fund?
     
  6. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    You can use this for inspiration.
    [​IMG]
     
  7. AE1N

    AE1N Ham Member QRZ Page

    Yes, don't get carried away with radials. Study the Elevated Ground Plane; it only needs 4 radials and is very effective. A "ground Plane" can be inches above the ground.
    Layne AE1N
     
  8. AI3V

    AI3V Ham Member QRZ Page

    Everybody talks about common mode and feedline radiation.

    And lots of money i$ $pent trying to eliminate it.

    But what if I told you you can prevent it!

    Yes, it's true!

    For a "ground plane" type of Marconi antenna it's simple,

    Take a length of coax

    Connect 1/4 wavelength of wire to the center conductor, and run the wire and coax in a straight line (preferably straight up :) )

    Now arrange two or more 1/4 wavelength wires, equally spaced, at right angles to the existing coax and wire

    Connect these "radials" to the coax shield.

    Sit back and enjoy a cool drink, knowing you don't have, well, IT.

    :)

    Rege
     
    NL7W and NH7RO like this.
  9. KM3F

    KM3F Ham Member QRZ Page

    Ya dat good Rege but for only one band I tink, unless ya say different.
    Him want to use multi band didpole , kem o sobee say..
    Anyway tell us please.
    Ya or Na. Hi hi.
     
  10. K5WY

    K5WY Premium Subscriber QRZ Page

    True, unless it's above your house.
     
    NH7RO likes this.

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