Do radials need to be straight?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W3WD, Jun 3, 2021.

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  1. W3WD

    W3WD Ham Member QRZ Page

    Stranded + insulated 18 AWG radials laying directly on the grass at the base of a vertical antenna-- online consensus seems to be that they don't need to be straight-- but does it help performance at all if they are?

    I have some small plastic composite garden stakes, and also some bricks-- any sense in trying to stretch the wires out from the antenna base and secure (tension) the ends to keep them straight?

    This is a quasi-portable installation that will be set up and taken down within a few hours.... I don't mind a little extra work to clean up the wires, but only if it will appreciably affect the performance of the antenna.

    Thanks!
     
  2. NK7Z

    NK7Z XML Subscriber QRZ Page

    How many radials, how long, and what frequency are you using the antenna on?
     
  3. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

    The vertical is a popular antenna among hams who lack the space for a beam or long wire antennas. In an electrical sense, a vertical is a dipole with half of its length buried in the ground or “mirrored” in its counterpoise system. Verticals are commonly installed at ground level, although you can also place a vertical on the roof of a building.

    At first glance, a vertical looks like little more than a metal pole jutting skyward. A single-band vertical may be exactly that! However, if you look closer you’ll find a network of wires snaking away in all directions from the base of the antenna. In many instances, the wires are buried a few inches beneath the soil. These are the vertical’s radials. They provide the essential ground connection that creates the “other half” of the antenna. Multiband verticals use several traps or similar circuits to electrically change the length of the antenna according to the frequency of the transmitted signal. (The traps are in the vertical elements, not the radials.)

    Vertical antennas take little horizontal space, but they can be quite tall. Most are at least 1/4-wavelength long at the lowest frequency. To put this in perspective, an 80-meter full-sized vertical can be over 60 feet tall! Then there is the space required by all those radial wires.
    You don’t have to run the radials in straight lines. In fact, you don’t even have to run them underground. But you do need to install as many radials as possible for each band on which the antenna operates. Depending on the type of soil in your area, you may get away with a dozen radials, or you may have to install as many as 100.

    Contemplate spending several days on your hands and knees pushing radial wires beneath the sod. It isn’t a pretty picture, is it? That’s why several antenna manufacturers developed verticals that do not use radials at all. The most efficient of these verticals are actually vertical dipoles. Yes, they are dipole antennas stood on end! There is no reason why this cannot be done. In fact, a vertical dipole can work quite well.

    So how does a traditional vertical antenna stack up against a traditional horizontal dipole when it comes to performance? If you have a generous radial system, the vertical can do at least as well as a dipole in many circumstances. Some claim that the vertical has a special advantage for DXing because it sends the RF away at a low angle to the horizon. Low radiation angles often mean longer paths as the signal bends through the ionosphere.

    Without a decent radial system, however, the vertical is a poor cousin to the dipole. The old joke, “A vertical radiates equally poorly in all directions,” often applies when the ground connection is lacking, such as when the soil conductivity is poor. If you can’t lay down a spider web of radials, dipoles are often better choices.

    http://www.arrl.org/verticals


     
  4. N4UFO

    N4UFO Ham Member QRZ Page

    Buy some of these: https://www.tractorsupply.com/tsc/product/sunguard-ii-3-8-in-fiberglass-step-in-post-3602233

    Then tune your radials, about 4 for each band and run them above ground on these stakes. You can make 4 tuned radials mounted above ground work as well as about 32 laying on the ground. Even IF the vertical is ground mounted. Trust me, I've done it. Had an 80/160m vertical up for a whole winter that way. Went to 32 on ground radials later, couldn't tell the difference. Worked DX all over both ways.

    As always... your mileage may vary, no warrantied implied or expressed, batteries not included. ;)
     
  5. K7MEM

    K7MEM Ham Member QRZ Page

    I doubt that bent radials will make any noticeable difference at all.

    I have a 43' ground mounted vertical (DXE Thunderbolt) in my yard (160-10 Meters). I currently have 16 radials buried in the grass. They are all pretty straight, but that's because I have the room. I may double that this summer, just to see if there is any noticeable difference. My area is like living in a park. There are no fences and vast areas of lawn. We can have fences, if we want, but no one seems to want one. Some people use a lawn service, but I take care of my own lawn. When the grass first starts to come up in the spring, I have to mow twice a week. So when I installed the radials, I made sure they were laying at the base of the grass and held the wires down with lawn staples, every few feet. A box of lawn staples can be had at Home Depot. It was tedious, but now I can mow the lawn without even thinking about the radials. The lawn staples are metal. I wonder if the lawn stables add anything to my counterpoise?
     
  6. K5UJ

    K5UJ Ham Member QRZ Page

    I don't know where this comes from, that radials work okay if they have a lot of bends. A ground system for a monopole should consist of an adequate number of radials (adequate means a lot more than most hams put down, like over 60 and more for 160 m.) all diverging equally and radially from the common ground point they should be bonded to at the base of the driven vertical element. Geometrically, each radial should be in a single plane with the driven element and at a right angle to it proceeding away from the driven element in a straight line. This is because of the way RF current is induced in the soil, making them return the currents most effectively. This means that for example, if you spiral wire around your feedpoint extending out in a coil pattern your ground system won't work as well. It is helpful and instructive to study ground systems used in broadcast facilities. This is a mature technology and the broadcast industry would certainly adopt less expensive methods and variations in the above if they could still meet proof of performance and efficiency requirements.

    Two points: When installing an inverted L, you can put bends in radials at a distance greater than the height of the L element. This is usually done with radials under the horizontal portion of the L to follow it on the ground.

    More radials are needed on 160 m.--why? Because assuming each one is at least a quarter wave length, they will be long enough to diverge to the point that with 60 radials, the separation between each radial will be too much for them to effectively collect and return induced ground currents and act as a good shield between earth and the monopole. On the high bands, especially 40 m. and up, the radials aren't that long and do not separate much at their ends, therefore not as many are needed.
     
    AK5B and SM6CJB like this.
  7. W1VT

    W1VT Ham Member QRZ Page

    If you have only a few radials, symmetry helps insure that they draw equal currents.
    If you have enough radials, it doesn't matter, as the current in any given radial is low.
     
  8. W3TKB

    W3TKB XML Subscriber QRZ Page

    I think that ideally the radial wires should extend as straight as possible from the center ground plate as possible, but if you have to take a few curves to negotiate around tree trunks, obstructive objects, or similar, it won't make that huge a difference.

    When I laid my radial field out, I wrapped the ends if each wire a couple turns around a 4" biodegradable lawn stake. I pulled the wire taught so it laid flat on the lawn, and drove that stake in. Then I put 4 or 5 lawn staples down the length of the wire, equally spaced, to hold it all down.

    The lawn has now completely consumed the radial field; you have to look real hard to see any wires. I can freely drive my lawnmower over it without fear of pulling up radials. I think if you just use the one lawn stake at the very end of the wire, and pull it taught, it will work fine for temporary usage.

    Brando 20210408_102317.jpg
     
    N5XH likes this.
  9. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    There is a reason they are called Radials and not "Zigzags". :)

    Still, there is no need for them to be tensioned. No need to be overly fussy about positioning them arrow straight.
     
    M0AGP and AK5B like this.
  10. KL7AJ

    KL7AJ Ham Member QRZ Page

    Absolutely not. Bent radials work just fine. The tuning will be a bit different, but that's it.
     

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