Antenna grounding is the creation of electrical connection between the equipment and a grounding device. The need for grounding is caused by the nature of their placement: antennas are installed in the open air. Therefore, there is a certain probability of lightning striking a metal surface. Grounding allows the voltage to be reduced to safe level for living beings.
Is grounding always necessary
Almost all experts recommend doing antenna grounding. Indeed, it is better to play it safe and ground the receiving device. but real danger hit exists only in cases where there are no objects within a 5-meter radius from the antenna, the height of which does not exceed 1 m (for example, a tree or a lightning rod). In this regard, it is wiser to ground not the antenna itself, but to place a diverting device next to it.
The main goal of lightning protection is to meet lightning before it strikes the protected object (in in this case on the antenna) and discharge the discharge to the ground. It includes three components combined into one electrical circuit:
- lightning rod;
- down conductor;
- ground loop (earthing switch).
Lightning rod
This device is installed near the antenna mast. Lightning rods are sold in specialized stores. It is also easy to build them with your own hands using an ordinary metal pin.
Down conductor
The component is the wire that guides the lightning to the ground loop. It should only be solid and have a certain section:
- Copper insulated or bare - 16 sq. Mm.
- Aluminum insulated - 25 sq. Mm.
- Steel - 50 sq. Mm.
If the antenna is not equipped with lightning protection, you will need to perform certain actions, the nature of which depends on external factors:
- design features of the support of the receiving device;
- type of roof;
- location of equipment.
If the antenna is installed on a grounded metal roof, for grounding purposes, connect the metal mast or lightning rod to the roof material. If the antenna is on a wooden support, the down conductor is the wire that goes along it to the ground electrode installed in the ground. By the same principle, grounding is organized if the receiving device is located on a non-metallic roof.
Grounding on a roof made of combustible materials has its own characteristics. For example, the upper section of the metal mast is connected to the zero potential point of the antenna and to the screens coaxial cables... A down-conductor is attached to the lower part of the mast, which is then directed along the wall of the building. Ground it by laying it on the bottom of a trench, the depth of which must be at least 1 m.
Earthing switch
To arrange grounding, they dig a hole 2-3 meters deep. A ground electrode is placed in it. A metal sheet, pipe, armature, or thick wire is suitable as a grounding device. The best option- a metal pipe with thick walls and a length of 1.5-2 meters. A wire with a diameter of at least 5 mm is welded to the ground electrode. The end of the conductor is fixed to the wall of the building in order to then bring the down conductor here.
Regulatory Requirements
Qualified specialists during installation work are guided by the requirements established by the European Committee for Electrotechnical Standards. The main document concerning grounding of antennas is called EN 50083-1.
This normative act stipulates necessary actions to prevent the destructive consequences of lightning striking the antenna. The requirements regulate work related to the protection of only permanent lightning protection systems or devices installed in campsites. They do not apply to amateur radio stations operating on the VSAT platform.
Several other documents also belong to normative acts, including:
- GOST P IEC 62305-2-2010.
- GOST R IEC 62305-1-2010.
- Rosstandart order number 795.
Potential equalization
Outdoor feeders, masts, various antennas, located completely or partially outside the protection zone, are exposed to the threat of lightning strikes. As a result, a requirement is put forward for a special system to avoid a dangerous potential difference. For this purpose, the following protective barriers are provided:
- Earthing television antennas, thanks to which the earthing switch is connected to the metal rack. An antenna is mounted on it.
- Equipotential bonding. The goal is achieved by connecting the earthed mast and the cables extending from it. If the antenna support is close to a building equipped with lightning protection, they are connected in one piece.
In the absence of a lightning protection system in the building, grounding for the antenna is carried out as follows:
- Establish grounding.
- Connect the grounding device to the antenna using a wire. In this case, the shortest distance between two points is chosen.
Note! Serious potential differences are inevitable if the wire is routed with significant bends around obstacles. In this case, inductance will appear in the conductors due to lightning strikes. In this regard, sparking is possible, which is unsafe from a fire point of view.
All down conductors from lightning rods (cable and rod) are connected to the ground electrode. The latter includes at least two vertical electrodes. The length of each of them is at least 3 m. The vertical electrodes are interconnected by horizontal ones (its length is from 5 m). The recommended cross-section for a copper electrode is 16 to 50 mm and for a steel electrode is 50 to 80 mm.
The choice of a place for fixing a television antenna and its orientation in space depends on many factors, including:
- kind of antenna;
- location of the land plot;
- the nature of the terrain;
- intensity of external interference;
- interference caused by indicators of power supply, type of AFD.
When installing a TV antenna on the roof, the mast is most often the base. A steel pipe with a diameter of approximately 35-40 mm is suitable for it.
An alternative to a metal product can be a wooden one - from a bar (50 to 50 mm). Such a mast is fixed to the rafter beams. The receiving device should rise above the roof along at least 2 m.If a wooden beam is chosen, a thick copper wire or a bus. The second end of the circuit is connected to a grounding device, which is either a bus or ground electrodes buried in the ground.
What not to do:
- Attach the antenna mast to ventilation ducts or chimneys, to electrical infrastructure, racks with communication wires, dormer windows.
- Secure the braces of the receiving device so that they are located near vibrators, electrical wiring, water pipes or window sills.
Varieties of lightning protection
There are two classic lightning protection schemes:
- Passive. The complete set of the system includes down conductors, lightning rods, grounding devices. All these components are networked. Lightning rods are usually rods or mesh structures.
- Internal. V this concept includes the entire list of actions to protect the elements of electrical wiring and equipment located inside the building from partial currents and pickups. Often, external protective systems do not save from these influences.
In accordance with the generally accepted concept, there are three lightning protection zones. Special devices (SPDs) are mounted along the borders of each of them. Such elements are also divided into three classes.
It is better to ask knowledgeable people about which method will be the best in your case.
Antenna Grounding - How to Organize
Here we will give the most basic, but effective method... So, next to the window through which the wires will be displayed, it is worth digging a shallow hole. Please note that its depth should not be lower than the soil freezing line.
It is worth putting a sheet of galvanized steel or any other metal object that does not corrode there. A wire must be soldered to this item. Carefully fill the object with earth so as not to damage the wire that we attach to the wall of the house. If the situation permits, then water pipes can also act as grounding.
In principle, that's all. But we want to note that no matter how simple the organization of grounding for antennas may seem, you should not do it yourself. At the same time, the most optimal solution purchase of professional grounding.
Despite the fact that it can be organized from scrap materials, they will hardly last for several years. And it's better not to imagine how you will find out that some components need to be replaced.
That is why, in order to be sure of the quality of the grounding of your antenna and to ensure high level protect your property, health and life of your loved ones, you should immediately contact qualified people.
* Feeder is usually called electrical network with all assistive devices with the help of which the radio frequency signal is conducted.
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Thunderstorms on our planet occur continuously. Experts have calculated that about a hundred lightning strikes the ground every second. Each of them is a powerful bundle of energy, sometimes with a current of up to 200,000 A. For this reason, forests are burning, houses are being destroyed, people are dying ...
At its core, lightning is a huge electrical spark that slips between the sky and the earth due to the opposite charge of the clouds and the surface. Just like with short circuit in the wiring.
The spark "breaks through" in the area where the distance between "plus" and "minus" is shorter. Therefore, lightning tends to strike freestanding objects that are closer to the sky, such as a tall tree or your home's antenna.
I will also note that electricity has a natural love for metal. If a heavenly spark is given a choice between a steel or a wooden pillar, all other things being equal, it will be drawn "to the irony."
In principle, the lightning protection system is surprisingly simple. The task is to meet lightning on the way to your antenna (roof) and make it change its original direction and, sliding along the wall, went into the ground nearby. Therefore, lightning protection consists of three main parts:
♦ lightning rod;
♦ down conductor;
♦ ground electrode ".
Note.
The lightning rod receives a lightning strike, transfers it to the down conductor, and that to the ground electrode, which extinguishes the discharge in the soil.
Now let's consider the case if there is no lightning rod near the antenna. Indoor television antennas do not need lightning protection. With regard to outdoor antennas, the need for protection is determined by the location of their installation.
Attention.
All external TV antennas, which are not located in the coverage area of the lightning rod, need lightning protection.
That is, if the outdoor antenna is located near tall buildings and structures equipped with a lightning rod (for example, near a factory chimney, high house, transmitter mast, etc.), it is not necessary to install a lightning protection device. If the antenna is installed on the roof of a detached (even one-story) house or on a building that is higher than the surrounding houses, lightning protection is necessary.
Attention.
The metal masts on which the antennas are installed must be grounded.
The best lightning protection is a metal pointed rod installed at the top of the mast (the tip of the rod should be at least 1.5 m higher than the antenna). The boom of the television antenna connected to the lightning protection circuit is shown in Fig. one.
Rice. 1. A boom of a television antenna connected to the lightning protection circuit
Attention.
All connections in the lightning protection system must be performed as reliably as possible: by welding, soldering or, in extreme cases, using threaded connections.
The lightning protection system must not violate normal work television antenna.
Case 1. The antenna is located on a grounded metal roof. Its grounding is provided by connecting the bottom of the metal mast to the roof.
Case 2. A loop vibrator is used in the antenna as a USS. It is connected to the metal boom at its midpoint, and the boom to the metal mast, so the mast must be grounded. The down conductor wire must be connected to the point of zero potential of the antenna, which can be:
♦ middle of uncut tube loop vibrator;
♦ the middle of the shunt of the range shunt vibrator;
♦ short-circuit bridge of the quarter-wave bridge of the split linear vibrator;
♦ metal arrow, etc.
In the absence of a point of zero potential, a high inductance choke must be included in the antenna circuit, which is connected to the special terminals of the antenna. In this case, the middle of the throttle tap will be the point of zero potential.
Case 3. The antenna mast is made of wood and is on the ground. It is necessary to lay a thick copper (steel) wire of the down conductor or a metal bus with a diameter of at least 5 mm along it. The shield of the drop cable must also be connected to the ground point of the antenna. The other end of the grounding wire must be connected to a grounding conductor, which can be either the wire itself or the bus, or metal parts specially buried in the ground.
Case 4. The antenna is installed on a non-metallic roof. In this case, the metal mast must be connected in its upper part with the cable shields and with the zero potential point of the antenna. The down conductor wire must be connected to the lower part of the mast, laying it along the wall of the house, and grounded by laying it along the bottom of the trench at a depth of 1 m. In this case, the length of the horizontal grounding tap must be:
♦ for clay soil - at least 2 m;
♦ for loam - 4 m;
♦ for black soil - at least 6 m;
♦ for stony soil - 10 m;
♦ for sandy soil - 12 m.
In fig. 2 shows the options for grounding antennas, which are most often used in the countryside.
Rice. 2. Options for grounding antennas in rural areas
It should be noted here that only the metal parts of the antenna need to be grounded. Do not ground electrical appliances and electrical products in which the chassis is connected to one of the AC mains leads.
Attention.
If such a product happens to be connected to an ungrounded mains conductor, connecting an external ground will result in a short circuit.
The simplest grounding conductors can be metal sheets, objects used in the household (basins, buckets, etc.), pipes, thick metal wire, etc. a ground electrode is placed in it, to which a steel conductor with a diameter of at least 5 mm has already been welded. If a steel wire is used as a ground electrode, then it is necessary to bury it in the form of a coil with a diameter of 1 m to a depth of 2 m. The length of the wire in a coil should be at least 20-25 m.
The best earthing switch can be considered a section of a thick-walled pipe 1.5-2 m long, buried to a depth of 2-3 m.In all cases, the end of the conductor from the earthing switch buried in the ground can be fixed on the wall of the house with staples, and a wire is subsequently attached to it grounding from the antenna.
One of the important tasks for ensuring the safety of a country house during a thunderstorm is the lightning protection of antennas, which, being the highest element of the roof, are most often exposed to lightning strikes. Therefore, every homeowner should take care to organize reliable grounding of the television antenna in the country. It is better to carry out such work, guided by the advice of experts in the field of lightning protection.
Some features
Contrary to the common misconception, the antenna itself, fixed to the mast, is not a lightning rod. At the same time, it often also does not fall into the protective field of the lightning rod mounted on the roof, and therefore needs to be equipped with a separate protective system.
In some cases, a lightning rod for roof protection is attached directly to the antenna, however, TV cable high potentials are possible inside the building - this is the result of non-observance of equopotentiality. As a result of such a skid, impulse overvoltages in the power grid, which can cause damage to electrical equipment and fires. To avoid this, it is necessary to properly equip the down conductor and grounding of the TV antenna in the country. Simple enough tips will help you with this.
Expert advice on the creation of protection and grounding of a television antenna in the country
The standard protection in this case is the down conductor equipment and the grounding of the TV antenna. One end of the down conductor wire must be connected to a ground electrode, the other - to a point of zero potential (such a connection object can be a metal arrow or the center of a loop vibrator tube).
The loop vibrator is in many cases used in the antenna structure as a signal catcher. It is connected at the midpoint with a metal boom that connects to the mast. With this design, the mast needs to be grounded.
If the country house has a metal roof with already mounted grounding, then the grounding of the TV antenna in the country house should be organized by connecting the lower part of the mast to the roof.
Earthing outdoor antenna- a responsible and difficult procedure. In order for the TV antenna to work properly, you need to carefully understand the process of connecting the ground.
Why you need to ground the antenna
Outdoor antennas pick up the signal better than indoor antennas. The latter only work well in areas where there is sufficient signal strength. Therefore, many owners of summer cottages and country houses prefer to install these types of antennas. But it takes a lot of skill to first install the TV antenna and then ground it.
Disputes about whether it is necessary to do grounding in the country are quite relevant. Most experts say that grounding is necessary to reduce electrical voltage to a level safe for humans.
When grounding, down conductors are connected to a grounding device (it consists of a grounding conductor and a ground electrode) in order to redirect the lightning discharge to the ground. Thus, the likelihood of fire from electrical discharge is significantly reduced.
It is necessary to make grounding in order to protect the antenna and equipment from atmospheric discharges. This is necessary so that during a thunderstorm, lightning does not strike the antenna, does not damage the TV, and also does not pose a danger to the residents of the house. In addition, with a grounded TV antenna, the image quality is improved, and there is less interference.
What you need to know before starting work
Grounding can only be carried out on a special grounding loop. It is easy to find a ground loop on the roofs of high-rise buildings: the masts of collective television antennas are connected to it. It is more difficult to make grounding in the country - for this you will have to install the ground loop yourself and carefully study the building codes and regulations regarding the installation of electrical installations.
The type of grounding depends on the following factors:
- support structures for installing a TV antenna
- type of roof
- the places where the antenna is installed
How to ground a TV antenna in the country
Grounding options can be as follows:
- device for a grounded plug socket. The antenna reduction plug must be plugged into the socket. Then the wizard solders the wire to the socket and connects it to ground
- grounded loop device. A two-wire cord (or double insulated wire) is soldered to the core and sheath of the drop cable. The master cleans the cores of the cord from insulation, solders them and connects the ground wire
- loop antenna ground. The wizard is grounding the antenna zero point. The advantage of the device is that it can be permanently grounded.
The master chooses one of two grounding schemes:
- passive (traditional). A relatively inexpensive and simple way is to install lightning rods, down conductors
- internal (all work to protect the electrical wiring in the room)
To check the grounding, you need to do the following:
- knock the sections of the connections of the contacts between grounding conductors and grounding devices with a hammer (to understand if there are gaps in some places)
- measure the resistance level ( it should be equal to 0.05 ohm)
How to make the installation of the ground loop
The grounding circuit must be an equilateral triangle. It must be at least one meter from the house. The contour can be divided into two segments:
- ground electrodes vertically driven into the soil (steel corners), interconnected by horizontal ground electrodes (strip steel)
- grounding conductor (round steel) connecting the circuit to the electrical panel
Rebar should not be used - it will rust faster than the above materials.
First you need to mark the territory... Then - dig a trench (about one meter deep). Horizontal ground electrodes will be laid here. After that, you need to drive in vertical ground electrodes (depth - two or three meters). Earthing switches are driven in at the vertices of the triangle, but not entirely - about twenty centimeters should be above the ground. After the master has finished driving in the ground electrodes, he must connect them using horizontal ground electrodes using a welding inverter.
The next step after assembling the ground loop- connection of the circuit with the electrical panel. Via welding inverter it is necessary to weld the grounding conductor to the grounding loop, and then lay the wire or steel strip to the electrical panel in the trench.
To prevent rust from appearing on the wires and to make them last longer, it is necessary to apply special anti-corrosion agents to them. It is impossible to paint the grounding with ordinary paints..
Delta tv antenna
A popular model of TV antennas is the Delta with an amplifier. An amplifier is needed for good signal, therefore, such a model is often installed in places where the signal from the telecentre is very weak. It should be noted that the effectiveness of the device depends on many factors:
- connection point
- installation height
- tv transmitter power
- noise level
- distance from the broadcast source
- terrain
The connection diagram for such a TV antenna can be easily found on the Internet. Masters share not only diagrams, but also photos, and also shoot videos in which they explain how to do grounding correctly, warn against common mistakes and give useful tips on connecting grounding not only in summer cottages, but also in apartments.
What not to do when grounding
Experts prohibit the following actions:
- fix the TV antenna mast to the ventilation duct, chimney
- fasten the extension of the TV antenna close to the electrical wiring, water supply pipes
- carry out grounding on network engineering: water pipes, pipes gas network, sewerage, heating
You can hear statements that it is enough to simply bury a bucket or other metal object in the ground and make grounding on it, but these are unsafe and ineffective methods, they cannot be followed. It is necessary to organize a potential equalization system.
Grounding TV antennas in apartments
Apartment owners install antennas on balconies and loggias. Usually, in these situations, additional grounding is not needed, since there is an independent grounding in the houses.
If you do not know how to properly ground, if you have not worked as an electrician, contact a professional. Grounding is a very difficult and extremely dangerous process. You may get an electric shock or fire.
It is best to consult a technician competent in the field of electrical safety. For example, assigning an admission group to a specialist speaks of his knowledge and skills. In addition, the foreman is responsible for the work performed. If you carry out the grounding yourself and an accident occurs, the responsibility for what happened will lie solely with you.
