RFI vertical ground plane

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KG5WKO, Dec 21, 2018.

ad: L-HROutlet
ad: l-rl
ad: Left-2
ad: L-MFJ
ad: MessiPaoloni-1
ad: K5AB-Elect-1
ad: Subscribe
ad: Left-3
  1. KG5WKO

    KG5WKO Ham Member QRZ Page

    I built a small 10 meter vertical as a test and gee wally it tunes nice at 28.520 mhz 50 ohm impedance. I have a very nice 1:1 Current isolation balum from balum works. Is there any reason one cannot be used on a vertical unlike a dipole? Or would something else be better such as ferrite beads?
    it is 4 feet off ground on PVC made of half hamstick three #14 insulated wire radials. Go figure after year of frustration this works but my wore antenna never has!!!
    Happy Holidays all
    73's
    TNX all who have bee helpful here.
     
  2. WR2E

    WR2E Ham Member QRZ Page

    You have a baluN, not a baluM, just sayin' before someone else does.

    BALanced to UNbalanced

    If you're feeding with coax, you may actually want an UNUN because the coax is UNbalanced and so is the antenna.

    The common 1:1 Guanella 'balun' should work for either case though.

    You may not actually 'need' a balun or unun for a vertical though, but it won't hurt to use one.

    Try to arrange the coax feedline so it doesn't 'couple' to any of the radials. This will help to keep common mode currents off the outside of the feedline and into the shack.
     
    Last edited: Dec 21, 2018
  3. AI3V

    AI3V Ham Member QRZ Page

    The radials do 2 things, they are the other half of the antenna,

    And,

    By being a quarter wavelength long, at right angles to the vertical part they form a rf "virtual ground",

    As long as the coax is below the radials they will prevent most current from flowing on the outside of the coax.

    If it was a power line on a printed circuit you would call them "quarter wavelength decoupling stubs.

    https://www.microwaves101.com/encyclopedias/quarter-wave-tricks#stubs

    If you wanted to keep the microwaves inside your microwave (you might wonder why there isn't a gasket between the door and box) you would call them "quarter wavelength chokes.

    https://everipedia.org/wiki/lang_en/Waveguide_flange/


    http://www.freepatentsonline.com/4137441.html

    Quarter wavelength wires and holes :) are a hams best friend.

    Rege
     
    NH7RO likes this.
  4. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Yes, an RF choke type device would be better than a balun, but no harm in using the balun if it's a current balun...it probably already is an RF choking device.

    At 4' above ground, it might work but just wait 'til you install it much higher -- it will work a lot better! In most cases, a whole lot better.

    10m isn't open so much nowadays, although it does have its moments. Even when the band is closed, in many places there's still local activity for chit-chatting (range similar to 2 meters) and it might pay to have not only the ground plane but also a horizontal dipole, as for local work, polarity matters and if local stations are horizontally polarized, the ground plane will be quite a bit "down" from a simple horizontal dipole -- as such, if possible, try both and use an antenna switch to see which one works better for any given contact.
     
  5. KG5WKO

    KG5WKO Ham Member QRZ Page

    I tested it at 4 feet and good without balun moving to 10 feet up and rdials sloped down to get 50 ohm it l00ks good and solid so may just wrap a few turns coax at base and test her in new year. With sun on a siesta we may not get anything but concept can be up graded to 20 so tnx all
     

Share This Page

ad: MultusSDR-1