RF ground whip antenna. Antenna and ground

Useful tips

One of important tasks to ensure the safety of a country house during a thunderstorm - this is lightning protection of antennas, which, being the highest element of the roof, are most often subject to lightning strikes. Therefore, every homeowner should take care to organize reliable grounding TV 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 popular belief, the antenna itself, fixed to the mast, is not an air terminal. At the same time, it often also does not fall into the protective field of a lightning rod mounted on the roof, and therefore requires the installation of a separate protective system.

In some cases, the lightning rod is attached directly to the antenna to protect the roof, but TV cable High potentials can be carried into the building - this is the result of non-compliance with equipotentiality. As a result of such drift, pulse overvoltages occur in the electrical network, which can cause failure of 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. Quite simple tips will help with this.

Advice from experts on creating protection and grounding for a television antenna in the country

Standard protection in in this case- This is down conductor equipment and grounding of the TV antenna. One end of the down conductor wire needs to be connected to a grounding conductor, the other to a point of zero potential (such a connection object can be a metal boom or the center of a loop vibrator tube).

In many cases, a loop vibrator is used in antenna structures as a signal catcher. It is connected at the midpoint to a metal boom, which is connected to the mast. With this design, the mast needs to be grounded.

If the country house has a metal roof with already installed grounding, then the grounding of the TV antenna in the country should be organized by connecting the lower part of the mast to the roof.

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Thunderstorms occur continuously on our planet. Experts have calculated that about a hundred lightning strikes the ground every second. Each of them is a powerful bundle of energy, with current sometimes up to 200,000 A. For this reason, forests are burning, houses are being destroyed, people are dying...

Essentially, lightning is a huge electrical spark that jumps between the sky and the earth due to the fact that the opposite charge of the clouds and the surface has formed. Just like when short circuit in electrical wiring.

The spark “breaks through” in the area where the distance between “plus” and “minus” is shorter. Therefore, lightning tends to strike free-standing objects that are closer to the sky, such as a tall tree or the antenna of your home.

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 “iron” one.

In principle, the lightning protection system is surprisingly simple. The task is to meet the lightning as it approaches your antenna (roof) and make it change its original direction and, sliding along the wall, go into the ground nearby. Therefore, lightning protection consists of three main parts:

♦ lightning rod;

♦ down conductor;

♦ grounding conductor".

Note.

The lightning rod receives a lightning strike, transfers it to the down conductor, and the latter to the grounding conductor, 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 require lightning protection. As for outdoor antennas, the need for protection is determined by the location of their installation.

Attention.

All external television antennas that are not located within the lightning rod’s coverage area need lightning protection.

That is, if outdoor antenna is located near tall buildings and structures equipped with a lightning rod (for example, near a factory chimney, a tall building, a radio transmitting 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 surrounding buildings, lightning protection is necessary.

Attention.

Metal masts on which antennas are installed must be grounded.

The best lightning protection is a sharp metal pin installed at the top of the mast (the tip of the pin should be at least 1.5 m higher than the antenna). The television antenna rod connected to the lightning protection circuit is shown in Fig. 1.

Rice. 1. TV antenna rod connected to the lightning protection circuit

Attention.

All connections in the lightning protection system must be made as reliably as possible: by welding, soldering or, in extreme cases, using threaded connections.

The lightning protection system should not violate normal work television antenna.

Case 1: The antenna is located on a grounded metal roof. Its grounding is ensured by connecting the lower part of the metal mast to the roof.

Case 2. The antenna uses a loop vibrator as a USS. It is connected at its midpoint to a metal boom, and the boom is connected to a metal mast, so it is necessary to ground the mast. The down conductor wire must be connected to the zero potential point of the antenna, which can be:

♦ the middle of the uncut tube of the loop vibrator;

♦ middle of the shunt of the range shunt vibrator;

♦ short-circuiting jumper of a quarter-wave split bridge linear vibrator;

♦ metal boom, etc.

If there is no point of zero potential, a high-inductance inductor must be included in the antenna circuit, which is connected to special antenna terminals. In this case, the middle of the choke tap will be the point of zero potential.

Case 3. The antenna mast is wooden, standing on the ground. It is necessary to lay a thick copper (or steel) down conductor wire or a metal busbar with a diameter of at least 5 mm along it. The shield of the reduction cable must also be connected to the neutral point of the antenna. The second end of the grounding wire must be connected to a grounding electrode, which can be either the wire or bus itself, 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 to the cable screens and to the zero potential point of the antenna. You need to connect the down conductor wire to the bottom of the mast, laying it along the wall of the house, and ground it, laying it along the bottom of the trench at a depth of 1 m. In this case, the length of the horizontal grounding lead should be:

♦ for clay soil - at least 2 m;

♦ for loam - 4 m;

♦ for chernozem - at least 6 m;

♦ for rocky soil – 10 m;

♦ for sandy soil - 12 m.

In Fig. 2 shows antenna grounding options most often used in suburban areas.

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 whose chassis is connected to one of the wires of the AC power supply.

Attention.

If such a product is connected to an ungrounded network wire, 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. To establish grounding near the house or the place where the antenna is installed, a hole up to 2 m deep is dug, a grounding conductor 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 grounding conductor, 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 the coil must be at least 20-25 m.

The best grounding conductor can be considered a section of 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 grounding conductor buried in the ground can be fixed on the wall of the house using brackets, and a wire is subsequently connected to it grounding from the antenna.

Antenna grounding is the creation electrical connection between the equipment and the grounding device. The need for grounding is caused by the nature of their placement: the antennas are installed in the open air. Therefore, there is a certain probability of lightning striking a metal surface. Grounding allows you to reduce voltage to a safe level for living things.

Is grounding always necessary?

Almost all experts recommend grounding the antenna. Indeed, it is better to play it safe and ground the receiving device. However, a real danger of being hit exists only in cases where there are no objects within a five-meter radius from the antenna whose height does not exceed 1 m (for example, a tree or a lightning rod). In this regard, it is wiser not to ground the antenna itself, but to place a tapping device next to it.

The main goal of lightning protection is to meet lightning before it strikes the protected object (in this case, the antenna) and divert the discharge to the ground. It includes three components combined into one electrical circuit:

lightning rod;
down conductor;
ground loop (ground electrode).

Lightning rod

This device is installed next to the antenna mast. Lightning rods are sold in specialized stores. They are also easy to build with your own hands using a regular metal pin.

Down conductor

The component is a wire that conducts lightning to the ground loop. It must only be solid and have a certain cross-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 receiving device support;
type of roof;
equipment location.

If the antenna is installed on a grounded metal roof, for grounding purposes, connect a metal mast or lightning rod to the roof material. If the antenna is on a wooden support, the current conductor is a wire running along it to a ground electrode installed in the ground. Grounding is organized using the same principle if the receiving device is located on a non-metallic roof.

Grounding on a roof made of flammable materials has its own characteristics. For example, the upper section of a metal mast is connected to the zero potential point of the antenna and to the screens coaxial cables. A current-carrying conductor is attached to the bottom of the mast, which is then directed along the wall of the building. It is grounded by laying it at the bottom of a trench, the depth of which must be at least 1 m.

Ground electrode

To arrange grounding, dig a hole 2-3 meters deep. A grounding conductor is placed in it. A metal sheet, pipe, fittings 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

When carrying out installation work, qualified specialists are guided by the requirements established by the European Committee for Electrotechnical Standards. The main document regarding antenna grounding is called EN 50083-1.

This regulatory act describes 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.

Regulatory acts also include several other documents, including:

GOST P IEC 62305-2-2010.
GOST R IEC 62305-1-2010.
Order of Rosstandart number 795.

Potential equalization

External feeders, masts, various antennas located completely or partially outside the protective zone are exposed to the threat of lightning strikes. As a result, there is a requirement for a special system to avoid dangerous potential differences. For this purpose, the following protective barriers are provided:

Grounding of television antennas, thanks to which the ground electrode is connected to the metal stand. An antenna is mounted on it.
Potential equalization. The goal is achieved by connecting the grounded mast and the cables extending from it. If the antenna support is located close to a building equipped with lightning protection, they are connected into one.

If there is no lightning protection system in the structure, grounding for the antenna is carried out as follows:

Install grounding.
Connect the grounding device to the antenna using a wire. In this case, the shortest distance between two points is selected.

Note! If you lay a wire with significant bends around obstacles, serious potential differences are inevitable. In this case, due to lightning discharges, inductance will appear in the conductors. 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 a grounding conductor. The latter includes at least two vertically located electrodes. The length of each of them is at least 3 m. Vertical electrodes are connected to each other by horizontal ones (its length is from 5 m). The recommended cross-section for a copper electrode is from 16 to 50 mm, and for a steel electrode - from 50 to 80 mm.

The choice of location for fixing the television antenna and its orientation in space depends on many factors, including:

type of antenna;
location of the plot of land;
the nature of the terrain;
intensity of external interference;
interference caused by power supply indicators, type of AFU.

When installing a TV antenna on the roof, the base is most often a mast. A steel pipe with a diameter of approximately 35-40 mm is suitable.

An alternative to a metal product can be a wooden one - made of timber (50 by 50 mm). Such a mast is fixed on rafter beams. The receiving device must rise above the roof at at least by 2 m. If a wooden beam is chosen, a thick copper wire or bus is laid along it. The second end of the circuit is connected to a grounding device, which is either a busbar or ground electrodes buried in the ground.

What not to do:

Attach the antenna mast to ventilation ducts or chimneys, to electrical infrastructure objects, racks with communication wires, and dormer windows.
Fix the guy wires of the receiving device so that they are located near vibrators, electrical wiring, water pipes or window sills.

Types of lightning protection

There are two classic lightning protection schemes:

Passive. The system includes down conductors, lightning rods, and grounding devices. All these components are connected into a network. Lightning rods are usually rods or mesh structures.
Internal. IN this concept includes the entire list of actions to protect electrical wiring elements and equipment located inside the building from partial currents and interference. Often external protective systems cannot save you from these impacts.

In accordance with the generally accepted concept, three lightning protection zones are distinguished. Special devices (surge protection devices) are installed along the boundaries of each of them. Such elements are also divided into three classes.

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♦ lightning rod;

♦ down conductor;

♦ grounding conductor".

Note.

The lightning rod receives a lightning strike, transfers it to the down conductor, and the latter to the grounding conductor, which extinguishes the discharge in the soil.

Attention.

All external television antennas that are not located within the lightning rod’s coverage area 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, a tall building, a radio transmitting 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 surrounding buildings, lightning protection is necessary.

Attention.

Metal masts on which antennas are installed must be grounded.

Rice. 1. TV antenna rod connected to the lightning protection circuit

Attention.

All connections in the lightning protection system must be made as reliably as possible: by welding, soldering or, in extreme cases, using threaded connections.

The lightning protection system should not interfere with the normal operation of the television antenna.

Case 1: The antenna is located on a grounded metal roof. Its grounding is ensured by connecting the lower part of the metal mast to the roof.

♦ the middle of the uncut tube of the loop vibrator;

♦ middle of the shunt of the range shunt vibrator;

♦ short-circuiting jumper of the quarter-wave bridge of the split linear vibrator;

♦ metal boom, etc.

♦ for clay soil - at least 2 m;

♦ for loam - 4 m;

♦ for chernozem - at least 6 m;

♦ for rocky soil – 10 m;

♦ for sandy soil - 12 m.

In Fig. 2 shows antenna grounding options most often used in suburban areas.

Rice. 2. Options for grounding antennas in rural areas

Attention.

If such a product is connected to an ungrounded network wire, connecting an external ground will result in a short circuit.

This issue becomes especially acute when it comes to properly protecting your home antenna. Antennas classic look are more often placed on the roofs of objects, satellite antennas are often hung on balconies or external walls of the building. Although there are options for installing them on the roof. This is explained by the fact that the grounding of antennas installed at enterprises is provided for at the design stage, and the requirements on this issue are formulated in sufficient detail in SO 153-34.21.122-2003, for facilities cellular communications- V
RD 45.162-2001 (Departmental standards technological design).
The antennas are placed openly, which suggests a very high probability of being hit by lightning. To minimize negative consequences such an event, special measures are applied technical protection antenna design, for example: comprehensive potential equalization, installation grounding. Practice shows that effective protection all connected devices that have high sensitivity, is only possible when executing pre-connection devices protecting against overvoltage.

Standards regulating lightning protection

Today, the vast majority of work carried out by qualified specialists providing lightning protection for antennas takes into account the requirements of European standards introduced by the European Committee for Electrotechnical Standardization CENELEC. First of all, we are talking about the provisions of the EN 50083-1 standard. This document regulates the basic measures of protection against the consequences of a lightning discharge striking an antenna. It is important to understand that the provisions of this standard apply only to devices that are permanent or installed in campsites. They are not amateur radio stations operating on the VSAT platform. In addition to the above, it is necessary to take into account the provisions of two more regulations: GOST R IEC 62305-2-2010 and GOST R IEC 62305-1-2010. Rosstandart introduced the provisions of these documents by its order 795-st, which is dated 11/30/10.

Antenna grounding and potential equalization

External feeders, masts and antennas of any type, located completely or partially outside the protection zone, are objects that can be struck by lightning. This determines the requirement to prevent the penetration of current from the antenna into the room using special system, preventing the occurrence of potential differences between its parts that pose a danger. Why are the following activities carried out:

grounding of TV antennas, ensuring the connection of the grounding installation with a metal stand on which the antenna itself is fixed. This is done using a special grounding wire;
potential equalization, which is performed by connecting a grounded mast and all coaxial cables emanating from it.

If the antenna mast is located in close proximity to a building that has lightning protection, then it is directly connected to the latter.
If there is no lightning protection in the building, a grounding device is initially installed, which is then connected via a special wire over the shortest distance directly to the antenna.
It is important to remember that a wire laid bypassing certain building elements can generate a significant potential difference due to the inductance in the wires resulting from a lightning discharge. And this, in turn, can cause spark discharges. Conductive elements (one or more) that have a maximum contact surface directly with the ground are used as grounding conductors. For example, a grounding switch based on the ZANDZ ZZ-000-015 modular grounding kit,
Each down conductor from rod and cable lightning rods must be connected to a grounding conductor consisting of a minimum of two vertical electrodes of at least 3 m in length, united by a horizontal electrode of at least 5 m in length. It is buried at least 500 mm and must have a minimum cross-section for copper equal to 50 mm 2, and for steel - 80 mm 2.

Where the antenna will be located on your site, and how it should be oriented, depends on sufficient large quantity external factors. The main ones can be considered:

the type of antenna you choose;
site location;
state of the area (relief);
levels and types of external interference;
interference caused by power parameters, type of AFU, etc.

If the antenna is mounted on the roof, then a small mast made of a metal pipe with a diameter of up to 40 mm, or a mast made of wooden beams (50*50) fixed to rafter beams, is used as a base. The antenna in these cases rises above the top point of the roof by 2000 mm or more.

FORBIDDEN:

attach the antenna (its mast) to ventilation ducts and chimneys, to electrical “goosenecks” and telephone stands, as well as to dormer windows.
fasten the antenna strings so that they pass close to its vibrators, or electrical wiring, to the pipes of the water supply system or window sills.

Types of existing lightning protection

Grounding satellite dishes and antennas of classical types is carried out according to one of two basic classical schemes:

Traditional lightning protection (passive).
With minimal financial investments, relatively simple installation and subsequent maintenance technologies, it allows you to fairly reliably protect antennas from lightning.
Part similar system protection includes down conductors, lightning rods, grounding conductors, which are combined into a single electrical circuit. Rod and mesh lightning rods are most often used as lightning rods.
Internal lightning protection.
This definition includes the entire range of works to protect electrical wiring elements and equipment located indoors from partial currents and/or interference, which, having overcome external systems protection could penetrate through existing systems communications. In this case, the possibility of negative impacts occurring is divided into the following groups: o a lightning discharge directly affected electrical equipment (entry through power lines, communication cables, grounding, etc.); o electromagnetic interference of various nature.

According to the currently existing zone concept, the lightning protection group under consideration includes three protection zones. Special SPDs are installed at the boundaries of zones ( protective devices), which are divided into SPDs of classes 1, 2 and 3.

Lightning protection requirements

If antenna “A” is installed outside the area protected by a lightning rod, then a number of protective measures will need to be taken to provide lightning protection for TV antennas and satellite dishes.
The list of these activities directly depends on a number of external factors:

support designs for antenna installation;
type of roof of the home;
places where this equipment posted.

If “A” is mounted on a roof with standard grounding (metal), then the mounting mast “A” is simply connected to the roof, which ensures grounding of the antennas in the country. Many antennas have a loop vibrator as a USS.

The main elements of an antenna lightning protection system, common to almost any design, are a grounding device and a down conductor. These elements should not have any effect negative influence for antenna operation. To do this, the down conductor must be connected to the place of “zero potential”, which can be located in various places in the antenna structure.
If there is no point with “0” potential, a choke (D) with a high inductance value is introduced into the electrical circuit of the installed “A”, which is connected to special antenna terminals. The middle of the bend (D) is the desired point.

On a mast made of wooden beams, a thick metal (preferably copper) wire is first laid to drain currents, the diameter of which cannot be less than 5 mm, or a copper busbar of a similar cross-section. The 2nd end of the grounding loop is connected to the ground electrodes. The role of such can be performed by the bus itself, or by elements of a grounding device dug into the ground.

RF ground whip antenna. Antenna and ground

Some features

Advice from experts on creating protection and grounding for a television antenna in the country

Is grounding always necessary?

Lightning rod

Down conductor

Ground electrode

Regulatory Requirements

Potential equalization

Types of lightning protection

Standards regulating lightning protection

Antenna grounding and potential equalization

Types of existing lightning protection

Lightning protection requirements

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