In RF engineeringradial has two distinct meanings, both referring to lines which radiate from or intersect at a radio antennabut neither meaning is related to the other. When used in the context of antenna construction, radials are physical objects: Wires running away from the base of the antenna, used to augment the conductivity of the ground near the base of the antenna. The radial wires either may run above the surface of the earth, on the surface, or buried a centimeter or so under the earth.
The ends of the wires nearest the antenna base are connected to the antenna system electrical ground, and the far ends are either unconnected, or connected to metal stakes driven into the earth. When used in the context of planning for a transmission system, radials are a concept used when describing a radio station's broadcast range : The radials in this case are several lines drawn on a mapradiating from the transmitter, with evenly spaced horizontal bearings.
The radial extends as far as the transmitted signal can reach either by calculation or by measurement. Stations transmitting at low frequencies like the mediumwave and longwave AM broadcast bandsand some lower shortwave frequencies, have frequencies so low that any feasible antenna is necessarily short compared to the wavelengththe most common being a quarter wave vertical antenna.
The radials at the antenna base provide a proper ground plane for the types of radio antennas used for long wavelengths. These electrically "short" antennas require grounding or earthing wires to function well. The radials are typically buried in the soil or laid on the soil in a flat, radial pattern.
These wires are called radialsground radialsgrounding radialsground system radialsor earthing radials. The ground system radials do not have to be absolutely straight nor absolutely horizontal. Although they provide an electrical "ground", they do not require any actual contact with the surrounding earth, even though advisable. When the radials are mechanically incorporated into the structure of a small antenna it is called a ground plane antenna.
For these antennas the radials slope off at an angle and are also called a skirt. Similar radiating wires can be placed on the top of antennas instead of at the base that serve an almost identical electrical function, but in that case the structure of radial wires at the top end of the antenna is called a capacitance hat or top loading.
When well designed, the ends of the wires in the ground system carry extremely high voltages. If elevated above the soil, the ends are often connected to ground rods as a safety measure, rather than to improve the function of the antenna. Any metal object within the near field of the radiator must also be tied to this system, or the metal will become energized with radio-frequency voltageand become an electric shock hazard, as well as potentially affecting or distorting the antenna pattern as a parasitic radiator.
In one unusual case, the strip mall built around the WSB AM tower near Atlanta has every metal object such as plumbing and ductwork grounded for this reason. The use of radial lines on a map for measurement, planning, and regulation of radio transmissions is called the radial method. It has no relation to grounding radials described above. In the field of transmission planning, radials are evenly spaced points vectors along evenly spaced lines bearings from a common point on a mapwhich are used to determine the average elevation above mean sea level AMSL within a radio station's broadcast range including broadcast stations and cellphone base stationsamong others.
This in turn determines the station's height above average terrain HAATwhich greatly affects its coverage area more so than effective radiated powerand therefore the potential for RF interference with other adjacent stations or cells. This information must be submitted with an application for a construction permit. The points used for calculation may differ if a directional antenna is used. In Europe and Asia, the use of radials has fallen out of favor since the s, and in many nations the radial antenna proof is only acceptable as an ancillary antenna proof.
Canada and Mexico, due to lower population densities, never implemented the fully complete radial models that the US FCC did. The radial method has been falling out of favor for methods based on Cartesian coordinates. Cartesian methods require more CPU time and memory to compute, but are understood to more realistically represent antenna systems.
Although many broadcasting regulators around the world had to find some way of regulating longwave and mediumwave antenna patterns and power, only the FCC chose to implement the radial method in its fullest form. The FCC decision to fully implement radials evolved from to Technology had changed, and by the s, computer terrain simulation of station interference and station patterns could be done on mainframes, typically using Cartesian or other non-radial methods.
The FCC rules on radials were relaxed in stages from to It is expected that the ruleset for radials will probably endure without change for a decade.
From Wikipedia, the free encyclopedia. Redirected from Ground radial.The SGC Smartuner gets energy into an antenna, but the design of an antenna is what controls what happens to the RF energy from there. For some antennas, the antenna is simply not complete without a radial system, or at least a counterpoise. Other types of antennas need no RF ground system at all. Most reference books on antennas provide solid guidance on radials and counterpoises, but only for antennas cut to a specific frequency.
To improve the RF ground conductivity for the ground current return path. Unless you live in a salt-water swamp, your ground conductivity makes a very poor path for the return of ground currents. This increases the ground losses and reduces the efficiency of an antenna that needs a good RF ground. To provide a counterbalance for the feed point of the antenna to reduce RF radiation back to the radio room. It is possible to be either a purist or a pragmatist in deciding what radials to put in place.DX Engineering Vertical 8040VA-1 Part 3, Installing the Mast and Base Assembly
Dipoles and Loops are the most common forms of balanced antennas in use. With a properly installed antenna fed by a Smartuner at the feed point, no RF ground is necessary. If the antenna is unbalanced, a radial system or counterpoise is necessary for operation. The radial our counterpoise system is connected to the Smartuner RF Ground. Base fed vertical antennas must have a good RF Ground system for efficiency. Vertical antennas can have radials mounted on or below the surface of the actual ground.
If the radial system is mounted above the ground, it is technically a counterpoise and takes the place of the actual ground. An equally good ground can be created by mounting well-bonded chicken wire or other grid material to form the ground plane near the antenna. Vertical antennas mounted high in the air will need to have a radial system mounted just below the antenna a ground plane antenna and connected directly to the Smartuner RF Ground. The ground plane on the antenna will shield anything mounted below it from RF, so a good place to mount the Smartuner for a raised vertical antenna is below the ground plane.
More radial wires are generally better. As the number gets larger, they improve the RF Ground less and less, to the point where there is no difference when adding one more radial to a system that already has installed. Generally, radials is the minimum that should be used.
Radial wires should be as long as the antenna wire if possible. If you must use shorter wires, keep them as long as possible and use extra radial wires. Antennas that use a vertical section as part of the radiator, such as the Inverted-L antenna, need to have a ground radial system just like a vertical antenna. This is often called a counterpoise. The RF ground wire in this case can be laid out in many ways, just so long as it does not cross over itself to form a loop. Indoors, such wires are often run under carpets or along walls, out of windows, or anywhere else convenient.
This wire will often have large RF voltages on it, so it should be kept away from people or insulated to prevent contact. Avoid connecting to a polluted ground. Building or Plant grounds can have a lot of other energy flowing through them that can get into your very sensitive receiver. RF Noise can come from many sources, particularly in industrial areas, and it can be present within the ground.
Avoiding this energy is one of the main reasons for creating your own ground system. While the Smartuner will provide a good match with a poor RF ground system and you will be able to transmit, your antenna efficiency will be low and you will be subject to RF problems that can make operation miserable at the very least.
I am wondering if 16 66' and 16 33' radials will be just as efficient for the higher bands as would having fewer radials separately cut for each band of interest. The same question differently: If I cut all the radials for 80 meters, would it negatively affect the signals of 40, 20, 10, etc.? The objective of any radial system is to avoid current in the soil by presenting a lower impedance alternative.
Current in soil is undesirable since it dissipates power in ohmic losses, reducing antenna efficiency. In an elevated radial system, the separation between the radials and the soil surface provides isolation, meaning the current in each is largely independent.
The soil and radials could be considered two parallel current paths, as such the one with the lowest impedance will take most of the current. Thus, it's important to minimize the radial impedance by ensuring some radials are resonant on any band used.
In a buried radial system, soil and radials are tightly coupled due to their proximity. Low ground losses are achieved not by providing a low impedance alternative but rather by effectively increasing soil conductivity by stuffing it full of copper. Thus, attempting to reduce radial impedance by cutting some of the radials to be shorter to be resonant on higher frequencies is futile or even counterproductive. Sign up to join this community.
The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Radial length for vertical antennas? Ask Question. Asked 1 year, 9 months ago. Active 6 months ago. Viewed 2k times. Does anyone know the answer to this or where I can find it?
MarqTwine MarqTwine 6 6 bronze badges. Is it designed to be a multiband antenna or is it just a single mast or wire with no traps, etc.? If so, height? They will be on the ground. This page may also be of use to you.Simple Antennas and Good Grounds. In small spaces, vertical antennas are very attractive. They can generate low takeoff angles for radiation, which means long skip distances. These low radiation angles are just what are need for communicating with DX such as "Our Neighboring States.
However, there are problems with installing verticals. Some commercial verticals address these problems and at least allege that you can use them without radials. Some like ground plane antennas have a built in ground plane radials, often drooping down to adjust the feedpoint impedance a bit. The drooping of the ground plane improves the match to 50 ohm coax, which is why ground plane radials on VHF antennas seldom stick straight out.
Configured like that, the feedpoint would be closer to 36 ohms. With the exception of the vertical dipole, a dipole on its end, vertical antennas are only "half there". The other half is a "reflection" in the ground. They rely on return ground currents and use the ground as part of the antenna system.
As a result, if the ground sucks, the antenna will also. It may load up nicely, but so does a dummy load. They all need a good ground underneath them to function well. Good grounds are hard to find.
Much soil has lousy conductivity. Salt water swamps are good, if you don't sink. Ground rods, copper-plated 8 foot steel stakes driven in the ground, might work in such a place if you use an array of them.
Unplated ground rods rust almost immediately and become useless for ground contact. Ground rods alone are usually no ground at all at RF, but they are very handy for safety and bleed off wind-generated static charge nicely. They may help moderate damage in case of a lightning strike, if you are lucky.
A lightning strike can easily carry 30, amps of RF current at about 2. That is a bit more load than most antennas are designed for.
So that leaves making your own "ground". This has been extensively researched since the earliest days of radio, and the bad news is clear:. AM] in Hilo [Big Island] over 15 years ago. Its ground system was installed by hand, pick and shovel. Five miles of 10 solid copper wire installed as radials, covering 5 acres. The result was one of the more efficient BC stations in Hawaii, especially on this island. The FCC wanted the station to lower the power from the 1 kW specified in the construction permit to watts.
Fortunately, one can cheat on this and suffer only minor loses, up to a point. Backing off from to 60 radials is not a big deal. Trying to get by with only four ground radials is certainly going to have a big negative impact on your antenna performance. There are indications that four ground laid radials detune an antenna greatly and make for six DB of power loss. Four elevated radials will work well if properly installed.When operators couldn't get a good earth ground, perhaps because they were on the second floor of a house, the common suggestion was to "use a counterpoise wire".
A grid of conductors parallel to a dipole, laid on earth or suspended above earth, is often referred to as a counterpoise. After all, the word "radial" hardly fits a group of parallel wires with no real connection to the antenna's feed terminal. Counterpoise, in popular Ham radio conversation, has always described a conductor or group of conductors serving as an RF ground.
Counterpoise definitions can be found in dictionaries. Here is the definition of "counterpoise" appearing in the Communications Standard Dictionary:.
A counterpoise is a c onductor or system of conductors used an earth or ground substitute in antenna systems. When we look at how the word has been commonly used, we see general use and dictionary definition agrees. This is how it is displayed:. In this case, using a 3D plotwe see Average Gain appear at the very bottom.
Average gain is also an indicator of improper modeling if average gain exceeds 1. Peak gain or maximum gain is another common performance indicator. It is displayed in the pattern plot:. The counterpoise is made much smaller, and this appears to have slightly better efficiency and average gain, but it is misleading. By looking at pattern we see significant reduction in the left area of pattern, and less gain at the lower, former maximum gain, angle.
This is still a useful comparison for peak radiation at long distances. An Inverted L, or any antenna with susceptibility to horizontal polarization, can give misleading ground efficiency results with compact or non-symmetrical counterpoises.
A full counterpoise below the flattop suppresses horizontally polarized radiation. By removing or reducing ground reflection below the horizontal antenna section, the low radiation angle vertically polarized Inverted L antenna is moved toward "low dipole mode". If we look at peak or average gain when changing to a counterpoise or ground system that no longer suppresses horizontal radiation, we can see what appear to be improvements. This keeps high angle "dipole mode" out of maximum gain or efficiency reports, especially when doing earth-height efficiency sensitivity reports or evaluations.
Otherwise, if we use an antenna susceptible to horizontally polarized radiation, we must compare absolute gain at low angles in all important directions. It is possible to "build" antennas that work very well in models, but rarely function like the model in real life. Some well-known authors, including one who pioneered early amateur modeling programs, have "invented" antennas that never achieve predicted results because they never included feed lines, or tested for sensitivity to feed line or matching system balance, or feed line or matching system loss.
This applies across the board to all antenna models, both receiving and transmitting. Those around me who do the most work and spend the most money, and have the poorest results, mostly willy-nilly change to a better system without thinking through changes, let alone documenting field strength changes.
Every time one local amateur changes antennas, the new antenna is always "killer".
Ground Radial Wire
He has gone from so many "killer" to even more "killer" antennas, yet skimmer shows him the same level as any other reasonable station from around here. Another common, but low value, comparison method is contest results, or DXCC totals. Scores trend upward over time as people improve things.
This is true for both skill, increased activity, and improved equipment. There are multiple causes at both ends influencing results, including noise level, activity, equipment, human factors, propagation, how enthusiastic we are, and even luck or fortune. We tend to operate more when we "feel good" about something new, and operating more always improves results. Finally, false claims and junk science universally depend on test errors, operator "feelings", or signal reports to support radial departures from good methods and science.
It is not all that difficult to install reliable reference antennas with proper construction and make A-B comparisons. The burden falls upon inventors of exceptional claims to provide reasonable comparisons with systems known to work to some standard, not on others to disprove them.
I can't imagine changing antennas here without any idea if the previous antenna was installed properly, or how the new antenna compared. I fell into this trap several times before in my life, and it slows my personal progress. I certainly have learned my lesson over the years. If I want to know something, I directly measure, or measure as directly as possible, what I want to know.Good for you! Depending on your soil, getting the radials installed well — and I mean well enough so they survive the lawnmower — can be a challenge.
Here in north Texas, with hard clay soils, I struggled. It had limited success, as some of them popped up enough for Mr. Lawnmower to chew them up. The Bermudagrass here seems to lift them more than bury them. I needed a better and easier way. At the suggestion of NS1L thanks Jim!
What a neat little machine! In trencher mode, it will dig a narrow trench, perfect for smallish wire, 1 to 1. Here is a short video of mine in action. It was set on full depth 1. Hint: decide in advance how many radials you want, plan for where the trenches will be, and do them in order in a circle. Try to avoid going back and adding more in between existing ones, because it is too easy to hit one of the existing ones, especially if it has already disappeared.
Wow, what a time and back-saver this thing is! You can see how I attached the radials to the base of the antenna on my 6BTV page.
Skip to primary content. Skip to secondary content.There are several ways to install your ground radials. Best wire to use is copper, of course because of its conductivity and resistance to corrosion. Typical 14 gage or 12 gauge house wire with the insulation left on his perfectly satisfactory. Any wire gauge 20 and above will be satisfactory. Copper clad steel wire is probably the next best. Aluminum definitely should not be used because it will deteriorate quickly in typical soil.
Also, stranded wire with its increased surface area will quickly deteriorate; do not use stranded wire. Radials can be rather small diameter wire since so many of them exist to share the return currents and they are in parallel with the ground currents in the earth as well.
Each radial is going to carry very little RF current. This is a misconception based on elevated or ground plane type elements. True ground laid radials designed to supplement ground return currents in the earth need not be resonant. Following we will show with several methods for laying down radial wires: one involves digging a trench, another one is just laying the radio wire on the lawn, while others suggest a elevated radial system.
These will be discussed following:. We will assume that you have a normal city lot with a lawn for your backyard. Here we will lay down radials in the grass and the grass will quickly grow over the radial wires.
In the past, I never seriously considered installing an extensive array of ground wires for my HF system due to the daunting task of making trenches to bury the wires. Having an array of ground radial wires has been a known need for this station, but the labor kept me from doing anything.
I tried to address the problem by driving lots of ground rods around the tower base. This certainly is inadequate! I have a typical city lot 70 feet wide and feet deep with the house plopped in the middle.