The principle of making an FM antenna for a radio with your own hands

The transmission and reception range largely depends on the quality of the antenna; the general conditions for the best operation of the antenna are: 1) the highest installation height; 2) the absence of interfering objects near the antenna (tall buildings, metal structures, etc.) and 3) a correctly selected power system.

Even more than long-wave and short-wave antennas, ultrashort-wave antennas require a high installation height and open space around them. Tall buildings and metal structures surrounding the antenna or rising on any side create significant losses of radiated energy.

The correct choice of feeder is especially important, on which the efficiency of energy transfer from the transmitter to the radiating part of the antenna depends. In order for losses in the feeder to be small, in addition to good quality electrical insulation, it is necessary that the feeder does not emit electromagnetic energy.

To reduce losses from feeder radiation, ultrashort-wave antennas use feeders operating in the traveling wave mode, and in order for traveling waves to propagate along the feeder, it must be matched with its load - the antenna, which occurs when the characteristic impedance of the feeder is equal to the input impedance of the antenna . If the matching is violated, standing waves are formed in the feeder, and its radiation increases, and consequently, energy losses increase, since the feeder radiation is absorbed by nearby building walls and other objects.

In amateur practice, three main types of feeders are used: a) from coaxial cable; b) from two parallel conductors isolated from each other by spacers and c) from two conductors intertwined with a cord.

Coaxial cable consists of an inner wire surrounded by a low-loss dielectric (polyethylene, polystyrene, porcelain) in the form of a solid viscous mass like rubber or beads. The insulation, in turn, is surrounded by an outer sheath, woven from thin wires or metal tape. The metal sheath is insulated with another outer layer of insulation that protects the cable from moisture. Characteristic impedance of the cable

depends on the distance between the inner core and the metal sheath and on the diameter of the core. If the characteristic impedance of the coaxial cable used is unknown, it can be determined by measuring the diameters of the inner core and outer metal sheath and calculating it using the formula:

Where:

• Z- wave impedance of the feeder, ohm,
• D - internal diameter of the outer metal shell, mm,
• d is the outer diameter of the inner conductor, mm.

The formula is valid for a cable that has beads as an internal insulator. For a cable filled with polyethylene, the resulting resistance must be multiplied by (formula):

where e is the dielectric constant of the insulator material, equal to 2.3 - 2.4.

Coaxial cable is widely used in VHF antennas, but radio amateurs do not always have it. You can make a well-functioning feeder yourself from two parallel wires. The distance between the wires is maintained using spacers made of material with good insulation (sticks made of organic glass, ebonite, porcelain, etc.). The characteristic impedance of a feeder made of two parallel wires can be calculated using the formula:

Where:

• Z-wave impedance of the feeder, ohm,
• l is the distance between the centers of the conductors, mm,
• r-radius of the conductor, mm.

From the calculation using this formula it follows that a parallel feeder cannot be made with a characteristic impedance of less than 200 ohms. In practice, feeders with a characteristic impedance of about 600 ohms are most often used.

In VHF work (for example, in television), feeders made of two insulated wires twisted into a cord have become widespread. This type of feeder has become widespread due to its simplicity and ease of manufacture, but it has large losses and gives significantly worse results than the two types described above.

Connecting an FM antenna

It is believed that we connect an FM antenna using three methods:

• In direct case, the design is an integral part of the device. Used by cell phones. Often in transmitting devices the antenna is made of a quarter-wave dipole, the body of the device serves as the ground. The active resistance is 30 Ohms, the reactive resistance is reduced by restructuring the resonant circuit. The antenna is asymmetrical; the equivalent current flows into the ground as it goes to the cascade. It creates losses, plus the alignment creates interference. In the case of stationary devices, good grounding helps; if the length of the bare wire is comparable to a tenth of a wave, the ground loop will begin to radiate, generating additional interference.
• In the case of non-resonant power supply, a conventional feeder is used, the characteristic impedance of which is equal to the characteristic impedance of the antenna. Ensures no losses and maximum signal level. There is a traveling wave in the line, the length of the feeder does not matter, and linear losses are significant. A meter of cable to the first amplifier stage reduces the sensitivity of the receiver. Avoid stacking coils on the floor. The excess cable between the receiver and the FM antenna is cut off. The problem of a long feeder is cut off by an active amplifier. We'll have to run the 12 volt cable to the roof, we'll stop worrying about the length. Solutions are appropriate where there is nothing else to do but listen to the radio. There is no Internet, television, or other communications. While most store-bought products are set to 50 ohms, homemade ones need to be properly matched. This is done using an SWR meter; a special screw for performing the operation has been found on automotive structures. Will significantly improve reception. Moreover, the antenna parameters and length change. Ideally, the SWR is equal to one, in practice it is allowed below 2.
• The resonant antenna power communication lines are the most curious phenomenon. There is only one problem: the signal transmission conditions strongly depend on the wavelength. The feeder must be a multiple of half. A radio station broadcasts in a certain spectrum, the frequency to which the receiver and FM antenna are tuned is the carrier. There are harmonics swarming around, which are actually useful. A carrier devoid of usefulness is of no value. For television, resonant communication lines lose their meaning; frequencies can differ threefold. It is impossible to maintain the conditions of a multiple of half the wavelength. The beauty is that the wave impedance of the line ceases to play a role. The antenna will be matched in such conditions. A curious feature is vigorously used to measure resistances. For example, using a line 5λ long, an antenna is examined to exclude errors and interference. To measure antenna resistance, the characteristics of the feeder do not play any role, as mentioned above. However, a number of practical amateur radio antennas are used at the resonant frequency, the harmonic frequency. Power supply using a resonant line will be a good way out. All that remains is to match the receiver input with the resistance of the FM antenna.

The importance of alignment is clear to readers. It is not enough to implement the FM antenna device; it is recommended to carry out coordination

Otherwise, those who are impatient can borrow a method from Wi-Fi: take a piece of a quarter-wavelength feeder (solid wire), peel it off the screen, solder it onto a connector, and plug it into the receiver so that the cable is positioned vertically. A primitive FM antenna, according to experienced people, performs well in the presence of waves on the air, therefore, it is suitable for impatient readers who do not want to coordinate the project. The simplest FM antenna, made with your own hands from any piece of coaxial cable, is capable of receiving. Feel free to take a television, the power will be lost.

We hope that we have given readers an understanding of the basic principles of designing FM antennas. By the way, don’t throw away broken gadgets. MP3 players, phones, and modems often contain what you need. Even a tiny factory FM antenna can give a homemade design a hundred points head start. Remove the required part and examine the electronics. It will come in handy. The time is not far off - we will program home controllers, create your own digital information processing devices.

Radio Basics: Parts

As you may have noticed from the previous section, creating static is incredibly easy. However, all radio stations today use continuous sine waves to transmit information (audio, video, various data). The reason we use continuous sine waves today is because there are many different people and devices that want to use radio waves at the same time. If you had any way of seeing them, you would find that there are literally thousands of different radio waves (in the form of sine waves) around you right now - TV broadcasts, AM and FM radio broadcasts, police and fire radios, satellite TV broadcasts, cell phone conversations, GPS signals and so on. It's also amazing how many uses there are for radio waves today. Each different radio signal uses a different sine wave frequency, and that is how they are all separated.

Any radio installation has two parts: a transmitter (transmitter) and a receiver (receiver). The transmitter intercepts some kind of message (this could be the sound of someone's voice, the image of a TV screen, data for a radio modem, or any other thing), encodes it into a sine wave and transmits it with radio waves. The receiver, of course, receives radio waves and decrypts the message from the sine wave that it receives. Both the transmitter and receiver use antennas to radiate and capture the radio signal.

How to do it yourself?

You will need it.

1. Soldering iron, solder and rosin, soldering flux. Instead of the latter, zinc chloride was previously used - it is prepared from tablets containing hydrochloric acid. These tablets are used by stomach patients. The source of zinc is any alkaline (salt) battery that has exhausted its service life: its “glass” is made of zinc.
2. Copper wire is a thick winding wire. An alternative is to twist all sorts of thinner stranded wires. For strength and reliability, they are soldered with solder so that the copper does not oxidize and the conductor does not “unravel.”
3. Dielectric base. It can be any board, plywood, chipboard, fiberboard, as well as homemade or industrial getinax (or fiberglass), from which the printed tracks have been removed. You can also use flat pieces of plastic from old, outdated electrical appliances.
4. Fasteners Bolts, screws, self-tapping screws, lock washers, nuts. Stock up on the right amount of them. Perhaps plastic “mounts” will also come in handy.
5. Coaxial cable (with a characteristic impedance of 50 or 75 ohms), plug (for the antenna jack of your receiving device).
6. The simplest locksmith tools. This can be a flat and figured screwdriver, pliers, side cutters, hacksaws for metal and wood, possibly an adjustable wrench and a hammer. An angle grinder and a drill will also speed up the antenna manufacturing process.
7. Waterproof varnish or paint. The conductors and the place where the cable is connected to them must be painted. This will protect them from corrosion caused by drops of water.

If you are not a radio specialist, then take a ready-made drawing. An example is a loop antenna. To make it, do the following.

1. Based on the dimensions from the drawing, bend a working element – ​​a “butterfly” – from copper wire.
2. Place it on a strong dielectric base, tying it to a wooden or plastic plate using “mounts”. A more “advanced” option is vertical stands on the edges and on a screw fastening. This is what “homemade workers” did in the 1990s, making antennas for receiving UHF television channels.
3. Solder the cable. The central core is connected to one side of the antenna, the braid to the other. There should be a gap of up to 1 cm between the parts of the figure eight and them. The dipole antenna is connected to the cable in the same way.
4. Paint the entire structure.
5. After the paint has dried, secure the structure to a pole or pipe. Tie the cable in several places to the support.
6. Attach the plug to the other end of the cable and raise the antenna higher. Point it at the broadcast city. If the distance is too great, there is no direct signal - they find a reflected one, for example, from a mountain or the tallest building not far from you.

The antenna is checked based on the reception quality of the desired radio station. Radio transmitters today are located in random cities and regional centers - many private radio broadcasters have appeared, making money from advertising. Radio stations are not located in the location of the city television tower (on the “telecenter” hill), but on a low mast about 30 m high. Not everyone wants to rent the “strategic height” of a city or region, broadcasting from the roof of a 9 ... 25-story building through a low-power (up to 100 W) FM transmitter.

There should be as little noise as possible in the background of the radio transmission. Radio reception must be in stereo format. It is impossible to receive a stereo transmission when the signal is weak - noticeable noise appears in its background. Rotate the antenna until you get the best quality. If the station is too far away and the noise remains, connect the radio amplifier to the cable break, next to the antenna.

A universal cable will help here, in which, in addition to the “coaxial”, a pair of additional wires are hidden under the outer protective sheath. The power line is isolated from the central conductor by the braid of the main radio cable. If there is no such cable, the amplifier’s power is supplied through wires to the radio receiver nearby, separately.

You can find out how to make an FM antenna with your own hands in 15 minutes below.

The antenna for the music center allows you to receive signals from popular radio stations, listen to songs and favorite programs. In some cases, the built-in amplifier is not enough: the sound comes through with interference or disappears altogether. In this case, industrial or home-made devices for receiving signals will come to the rescue. Homemade antennas can be made quite easily and quickly from scrap materials.

What to choose

Today, the manufacturer offers not just one, but a whole host of amplifier options for a car antenna.

Domestic manufacturer

Amplifier Triad

It is interesting that our domestic manufacturer also offers a whole line of products called Triad. All models deserve praise, and especially the amplifier for the car radio antenna Triada-304 Dalnoboi, which is equipped with the function of turning off the device and operating in the FM/AM/VHF radio bands.

Foreign manufacturer

Amplifier from Prologi

Among foreign manufacturers, Prologi products take pride of place. For example, their model TFB-100 is capable of amplifying digital and analogue signals and simultaneously working with two antennas.

On your own

Yes, there is such an option. For radio amateurs, it offers special kits from which you can assemble a full-fledged amplifier with your own hands. Again, homemade amplifiers are assembled using a two-stage circuit. Well, now you have learned how to strengthen the radio signal in your car radio. Installing an amplifier purchased or made by yourself will not take much time and effort. All you have to do is follow the instructions, watch the video review and study useful photo materials. The price of amplifiers varies and it all depends on the reception range, as well as the manufacturer.

Useful tips

It is important to choose the right location for installing the antenna. A car body can be both a kind of indicator of improved signal reception quality and an interference

The best place for mounting is the center of the roof. There should be no foreign metal objects near the catcher. It is better to purchase combined antennas for receiving various communication signals ready-made.

The installation must be protected as much as possible from the influence of the external environment so that contacts do not oxidize and parts of the entire structure do not rust.

An antenna made by yourself is an effective way to save money, improve the quality of signal reception, and allow you to technically modify the radio in your own car.

Simple antenna amplifier for VHF(FM) receiver

VHF FM radio has become an indispensable attribute at home, in the car and in the country. And one of the problems that arises during its operation is ensuring the required quality of reception at a great distance from broadcasting stations.

Unfortunately, not all radio receivers have good sensitivity, so when you move several tens of kilometers away from radio stations, for example, while staying in the country or traveling out of town, the quality of reception deteriorates significantly.

Installing effective receiving antennas on a car or portable equipment is very difficult or simply impossible.

A way out of this situation may be to use a low-noise antenna amplifier at the input of the radio receiver. If the radio receiver is multi-band and has one antenna input (for example, a car), then the amplifier must amplify the signals of this particular range and transmit signals from others without loss.

In addition, in city conditions, when the level of radio signals and interference is significant, such an amplifier must be turned off to avoid crosstalk distortion.

If reception is carried out far outside the city, then the amplifier can be made non-switchable.

Homemade antenna

Anyone can do it; for this we need a few simple tools that are available in every home:

• A piece of copper wire.
• An ordinary kitchen knife.
• Pliers.

Note that not in all regions of our country the FM signal stably covers the entire territory. In some remote locations, the conventional built-in antenna of a music center is not enough. In this case, device owners begin to try to strengthen the signal on their own. Most often you can see a standard FM antenna wrapped in wire. In other cases, this wire is placed outside the window (for example, through an open window), in the hope that it will somehow strengthen the signal. Indeed, such practice often helps, and the radio still manages to be picked up.

So, let's take a closer look at how to make such a standard antenna amplifier with your own hands. This is done in stages:

1. Take a piece of copper wire.
2. Measure the length you need and cut using pliers or wire cutters.
3. Now strip the cut piece of wire using a regular knife.
4. Next, you should securely tape the cleaned wire to the existing antenna and try to catch the signal.

If significant improvements have not occurred, then you should pay attention to the back of the music center. In the area where the plug sockets are located there is often a so-called input for additional antennas

Some manage to amplify the signal by inserting a wire into this socket, but it is worth noting that such a practice can lead to unstable operation of the device as a whole, and sometimes to breakdowns. Moreover, the effectiveness of this method seems very doubtful.

If amplification with a wire-type device does not help, you can try to assemble a rod antenna. It is highly directional and more resistant to urban interference. Most often, it is made from an existing old television antenna, taking into account the fact that some television broadcasting frequencies have shifted or even switched to online or satellite broadcasting.

In order to make it yourself, you need:

1. Secure the load-bearing structure to the outside of the building.
2. Plug the wire into the corresponding socket of the music center (to make it you will need a plug for the corresponding socket and the ability to work with a soldering iron).
3. Search for radio stations.

Of course, there are options for homemade antennas with a more complex manufacturing algorithm, but their assembly will require much more skills and time. Wire and whip antennas are the simplest options available to any user when it is necessary to improve the signal using improvised means.

Transformer

The antenna, equipped with a reflector and director, has a pronounced one-way directionality. At the same time, its efficiency increases, since energy is emitted or received in one main direction and directions close to it.

When the distances between the emitters are less than a quarter wavelength, simultaneously with an increase in directivity, the radiation resistance of the dipole decreases. A feeder with a resistance of 70 ohms then turns out to be unsuitable for direct connection to a dipole due to the large difference in resistance and the resulting mismatch.

Mismatch leads to the formation of standing waves in the feeder and to an increase in its radiation, which creates large energy losses. Dipole matching in a directional antenna with a two-wire feeder can be achieved by using a transformer between the antenna and feeder. The structure of such a transformer is shown in Fig. 4.

In addition, matching can be obtained by using a loop dipole instead of the usual one. When a loop dipole operates in a complex antenna, its radiation resistance is reduced, and power can be supplied directly by a feeder from a coaxial cable with a resistance of 70 ohms.

The dimensions of the antenna in this case are as follows: length of the loop dipole l = 142,500/f (hereinafter l - in mm and f - in MHz); the length of the reflector is 5% longer than the length of the working dipole; the length of the director is 4% less than the length of the working dipole; distance from the reflector to the dipole l = 45,000/f. The distance from the director to the dipole is l = 30,000/f.

Rice. 4. Transformer device for matching the working dipole with a 600 ohm feeder. 1 - dipole; 2 - coaxial cable 70 ohm; 3 - feeder made of parallel wires with spacers.

Connection and configuration rules

The design of a radio for a car involves connecting 3 wires. The first is required for grounding and installation of the receiver. It is connected to a metal fastener and then tightened. The second is for food. It is connected to a wire extending from the receiver.

The third is necessary to establish contact. Connects to a special connector in the radio. Sometimes combined with a power cord. Wires are laid only when the installation is completed.

The antenna must not be mounted next to other metal elements.

If the device is installed outdoors, it must be protected from adverse environmental conditions. If this is not done, the metal may oxidize due to rain or snow, which will lead to malfunctions of the device.

AUGRA installation options

Installation of automatic control gear must comply with the following requirements:

• ensuring reliable fastening of the radio receiver to the car, preventing movement when exposed to various mechanical loads (wind, bending, etc.);
• ensuring tight contact with the body, which acts as a mass, which significantly reduces the level of interference and improves signal quality.

All options for installing a receiving radio antenna come down to three main methods for fixing the automatic control gear on a vehicle:

• mortise mounting using a through hole drilled in the roof or other part of the body;
• magnetic mount using a magnetic antenna base;
• a pin mount, which is a mechanical fixation of the antenna rod for a car radio on a special clamp-type bracket.

APRA mortise mount

The mounting pin of the radio antenna base is inserted into the through hole, and a nut is screwed onto it from inside the passenger compartment. The advantages of the “mortise fastening” method include:

• the strength of the device, reducing the likelihood of it being stolen;
• stability of the operating parameters of the antenna-feeder system after installation.

Among the disadvantages, the following circumstance is noted: the edges of the drilled hole are centers of corrosion of the metal body, therefore it is recommended to use standard technological holes.

Important! In the fastening area, it is necessary to strip the metal of paint to ensure reliable conductive contact of the nut, as an element of the antenna, with the metal of the car body. On rice

Below is the antenna base with a pin and a hole in the roof of the car prepared for installing the AUGRA

In Fig. Below is an antenna base with a pin and a hole in the roof of the car prepared for installing the AUGRA.

Antenna base for flush mounting

Magnetic mount APRA

The magnetic fastening of the antenna is provided by magnets located at its base - the sole. Magnets can be purchased separately from the antenna device. The most popular magnets are with diameters from 90 to 170 mm. The stability of the automatic control gear directly depends on the diameter of the magnet.

The antenna is attached to the magnet through two types of connectors:

• The DV connector is adapted to most antenna systems and allows for adjustment of the installation angle;
• The PL connector is more reliable in terms of maintaining strict vertical installation.

In Fig. Magnetic antenna mounts with DV and PL bases are shown below.

Magnetic antenna mounts with DV and PL bases

The advantages of the magnetic fastening method include the following points:

• ease of installation or dismantling;
• relatively high stability of the automatic control gear is ensured while maintaining the optimal size of the magnetic base;
• capacitive coupling of the magnetic base with the metal of the body creates a kind of imitation of “mass” necessary for the operation of the receiving antenna;
• the ability to move when setting up equipment.

Disadvantages include:

• low strength of fixation on the body;
• ease of abduction;
• the possibility of shifting, which leads to the need for additional adjustments.

Recommendations

If we talk about recommendations for the creation and use of such antennas, then first of all we should note several.

• There should not be any metallic foreign objects near such a device. Otherwise, they may interfere with the reception of the signal or reflect it, which will also negatively affect the quality of its reception.
• Care should be taken to protect the antenna from exposure to natural factors. Otherwise, its parts may rust and sooner or later the device will simply fail.
• In most cases, it is necessary to make drawings before starting work, where you need to describe in detail the dimensions and dimensions of the device, its type, as well as the algorithm of actions for its creation. This will make it possible to quickly and accurately implement one or another idea and obtain a high-quality antenna for receiving a stable FM signal.

How to make a radio antenna with your own hands in 15 minutes, see below.

Wave Propagation

• Line of sight propagation. Among all the distribution methods, this is the most common. The wave travels the minimum distance that can be seen with the naked eye. Next, you need to use an amplifier transmitter to increase the signal and transmit it again. Such propagation will not be smooth if there is any obstacle in its transmission path. This transmission is used for infrared or microwave transmissions.
• Ground wave propagation from a transmitting antenna. The wave propagates to the ground along the contour of the Earth. Such a wave is called a direct wave. The wave sometimes bends due to the Earth's magnetic field and hits the receiver. Such a wave can be called a reflected wave.
• A wave propagating through the earth's atmosphere is known as a terrestrial wave. The direct wave and the reflected wave together produce a signal at the receiving station. When the wave reaches the receiver, the delay stops. Additionally, the signal is filtered to avoid distortion and amplification for clear output. The waves are transmitted from one place and where they are received by many transceiver antennas.

Homemade options for DVB-T2 reception

First of all, let's decide what exactly we are catching.

In Russia, after the introduction of federal digital broadcasting throughout the entire territory (with the exception of some areas where it turned out to be cheaper to allow all residents to use satellite broadcasting for free), two multiplexes should be received - a set of 20 channels included in the state package. Access to them is free, they are transmitted, although digitally, but openly on the decimeter range.

Therefore, it is necessary to assemble a television antenna designed to receive the UHF range.

Is a homemade antenna difficult?

Difficult! Easy!

There are many design options suitable for receiving a DVB-T2 television signal: the UHF range and the conditions for its reception have been thoroughly studied by generations of physicists and radio amateurs.

Here is a comparative table of characteristics of the simplest and most effective homemade products used for receiving digital television:

Of course, this is not a complete list of what you can do with your own hands. However, the schemes of such designs as the Kovachev, Turkin and “wave channel” antennas have significant disadvantages:

• too complex, and the efficiency is not so high that it makes sense for an untrained person to try to make them;
• long-range, but narrowband. For example, if both multiplexes are separated by 6 or more channels (which is regularly found with repeaters in rural areas), you will have to make and configure two antennas of the Turkin design, one for each multiplex, and then select a matching transformer and level it (ideally to the nearest millimeter) cable length.

Next, we will consider each option separately, highlighting the main pros and cons.

Basic communication characteristics

Antennas are the main components of any electrical circuit because they provide the coupling between a transmitter and free space or between free space and a receiver. Before talking about antenna types, you need to know their properties.

An antenna array is a systematic deployment of antennas that work together. The individual antennas in an array are usually of the same type and are located in close proximity, at a fixed distance from each other. The array allows for increased directivity, control of the main radiation beams and side beams.

All antennas are characterized by passive gain. Passive gain is measured by dBi, which is related to a theoretical isotropic antenna. It is believed to transmit energy equally in all directions, but does not exist in nature. The gain of an ideal half-wave dipole antenna is 2.15 dBi.

EIRP, or equivalent isotropic radiated power of a transmitting antenna, is a measure of the maximum power that a theoretical isotropic antenna would radiate in the direction of maximum gain. EIRP takes into account losses from power lines and connectors and includes actual gain. EIRP allows real power and field strength values ​​to be calculated if the actual gain and output power of the transmitter are known.

What function does it serve?

The only function of an external (additional) antenna is to increase the reception range in areas of very weak radio communication. This is how long-range and ultra-long-range techniques are implemented. Car antennas are in great demand among truckers who need high-quality communications and reception over many tens of kilometers. Radio stores often sell antennas with a very short pin - only 10-25 cm. A non-professional, who does not particularly understand radio as such, takes what they give - he does not realize that if the pin is increased to the required length, the reception quality will noticeably improve .

A tribute to the fashion for miniaturization and lightness of any devices takes over - as a result, the quality is far from expected.

VHF antenna triple vibrator

The parallel feeder is connected to the halves of the middle wire broken in the center. The dimensions and structure of such an antenna are shown in Fig. 3. The radio communication range on VHF can be significantly increased without increasing the transmitter power by using an antenna pin; 2 - Insulating sleeve; 3 - copper or aluminum tube; 4- feeder; 5 - insulators; 6 - mast. Length of pin and tube 71 250/f; tube diameter 30-40 mm

If a second wire is placed parallel to the half-wave dipole at a distance of about a quarter of a wave, it will change the directivity characteristic of the antenna. Such a wire (called passive, since it is not connected to anything), slightly longer than the dipole, is placed behind the working dipole and acts as a reflector, amplifying the radiation in the opposite direction.

A passive radiator shorter than the dipole, placed about a quarter wavelength in front of it, amplifies the radiation in that direction. Such a wire is called a director.

Rice. 3. VHF antenna - triple vibrator.

How to choose an amplification module

The first criterion by which an FM signal amplifier for a car radio is selected is its power supply type. There are two types of devices on the market today.

1. With external power supply. Such an amplifier has a tap, one wire for connecting to the vehicle’s on-board network.
2. Powered by antenna cable. Such devices connect only to a certain class of radio tape recorders. The latter must have the option of power supply via an antenna cable.

Regardless of the technical solution, connecting the antenna amplifier to the car radio is not difficult. However, the main thing is to buy a device with the right characteristics. The criteria for choosing the optimal model are as follows.

1. The frequency band is selected depending on the type of radio and the radio tuner installed in it. If this is an old cassette model that receives short, medium and fm waves, a wideband amplifier will be required. For modern radio tape recorders, a narrowband model operating only in the FM range is sufficient.
2. Type of antenna to be connected. For conventional pin models, a conventional amplifier is used. When using directional (also called dipole) antennas on a car, a more complex device will be required. The circuit solution includes a matching module.
3. The gain should be between 10 and 30 dB. Today you can buy models with a higher indicator. However, it is not recommended to do this in a large number of cases.

It is worth talking in more detail about choosing the optimal gain. It is determined not only by the desired reception range. The fact is that the maximum power of the car radio amplifier determines the final signal level at the device input. However, there is a technical limit to its increase.

If the installed antenna amplification module is very powerful, and the car is located in an area of ​​reliable reception, in a large city, the radio will simply stop receiving the radio. The protection system will work. The amplification device, generating an excessively strong signal, will take its value beyond the technical limit. As a result, in order to protect the primary reception circuits, roughly speaking, the antenna input will be blocked.

When the actual use of the car involves both its movement in the city and travel far beyond its borders, it is recommended to install an amplifier blocker. This is a circuit that turns it off if necessary, making a bypass to the main cable channel of the antenna. You can buy an amplifier that turns itself off when a certain limit signal is reached at the output.

Antenna measurement coordinate system

When looking at flat models, the user will be faced with the azimuth of the plane and the height of the pattern plane. The term azimuth usually occurs in reference to the "horizon" or "horizontal", while the term "elevation" usually refers to the "vertical". In the figure, the xy plane is the azimuthal plane.

The azimuthal plane pattern is measured when the measurement is made by moving the entire xy plane around the transceiver antenna under test. An elevation plane is a plane orthogonal to the xy plane, such as the yz plane. The elevation plane plan traverses the entire yz plane around the antenna under test.

Patterns (azimuths and elevation plots) are often displayed as polar plots. This allows the user to easily visualize how the antenna radiates in all directions, as if it were already "targeted" or mounted. It is sometimes useful to draw radiation patterns in Cartesian coordinates, especially when there are multiple sidelobes in the patterns and where sidelobe levels are important.

Antenna connection

Even a properly designed and well-made antenna will perform poorly if there are errors in the connection.

The following conditions must be met:

1. Use shielded cable.
2. Securely solder contacts and connectors.
3. Make sure that the core and screen are tightly connected to the radio input group.
4. Ground the antenna.
5. If there is interference when powering the radio from the network, when there is no ground wire in the socket, it is better to connect the radio or transistor to ground. For this purpose, most devices have a special socket or terminal.

If the reception quality is not satisfactory, and changing the location and direction of the antenna does not help, you will have to install an amplifier.

A simple and low-cost circuit of such a device is assembled, for example, on an RFMD SPF5043Z microcircuit. The advantage of the design is that the board can be made without chemicals on a 2-sided PCB measuring 15-20 mm and placed in a shielded case.

Assembly instructions

You can make both inactive and active (with an amplifier) ​​devices with your own hands. The production technology consists of several stages:

• preparing the necessary tools;
• direct assembly;
• fastenings to the machine body;
• connections.

Assembling different types of antennas for a radio with your own hands differs significantly even in the selection of necessary tools.

Production of an inactive installation

Passive antennas without an amplifier are considered quite simple in design. To create such a device, you will need:

• copper wire (diameter from 1.5-2 mm);
• high quality nut;
• good file;
• screwdriver;
• thermal glue (can be replaced with heat shrink tube);
• screw (diameter M5);
• lock-nut.

Assembly is carried out in stages. For this:

1. Take copper wire and twist it to a length suitable for a particular car.
2. The resulting spiral is placed on an M5 screw, secured with a nut and a lock nut of the same size (soldered on top). The structure is treated with thermal glue, or wrapped using heat shrink tubing.
3. The surface is sanded with a file. This procedure is done provided that the spiral has been treated with glue (only after the substance has completely dried).
4. Install a homemade antenna. The spiral blank is inserted into the hole made (at the base), and the wires are connected.

To give the installation an aesthetic appearance, a film is glued onto it, treated with a primer, and painted. The passive device is ready.

Creating an active fixture view

A special feature of this technique is the presence of equipment that enhances signal reception. When creating internal active installations, frame structures are used. This requires the following tools:

• copper wire, always with insulation (diameter - 2 mm);
• home amplifier (a television device will do);
• high-quality soldering iron;
• a connector that is suitable for a radio;
• good nippers;
• glue.

An amplifier housing designed for a regular home antenna is often used as the basic basis for the device. Solder a wire to it, which, in turn, will connect to the radio. This is necessary for the amplifier to receive and transmit signals.

The antenna plug is connected to the socket, and a connector is mounted at the other end of the wire. The power cable for the amplifier in car radios is considered the control cable; it is painted blue.

An active type receiver is mounted on the roof of the car so that signals are well received. To do this, two holes are drilled in the housing - mounting and auxiliary. The antenna wire is laid around the perimeter of the driver's door, fixed with glue. After installation on the roof of the car, attach the (side) cable to the rack and carefully connect it to the car radio.

Installation and connection features

Traditionally, active types of antennas for radios are installed on windshields in the upper right corners or behind rear-view mirrors. Passive installations for receiving signals are placed on car bodies, usually mounted on roofs.

Any antenna should be mounted only on a clean surface. For installation, use glue or masking tape, bolts, nuts, lock nuts for grounding, and a drill suitable for the diameter of the antenna wire. The mounting area must be degreased with a special cleaner.

Fix the devices with glue or masking tape. After installation, wires are laid from the antenna to the radio. This is done either around the perimeter of car doors or windows, or directly around the interior through special openings.

The design of an ordinary car antenna has three wires:

1. The first is used to ground the device. It attaches to a metal mount on the body. Secure the wire with a bolt, a strong nut and a lock nut.
2. The second is used to power the device. It is connected to the wire coming from the radio.
3. The third is a contact one; it is connected to a specially designed connector.

Most often, the second wire is combined with the third; by connecting the power, the contact function is activated, and the antenna begins to receive the signal.

Step-by-step installation instructions on the roof

If the supplied cable is not long enough, an additional one will be required. The cable must be braided and have a resistance of 75 ohms.

1. At the installation site, it is necessary to drill two holes: one with a diameter for mounting the antenna and one with a diameter of 5 mm for an auxiliary one.
2. The metal at the installation site is cleaned from the inside of the cabin.
3. To avoid corrosion, the installation site is treated with mastic on the inside of the cabin and sealants on the outside.
4. For installation, it is necessary to make an insulator (spacer) from copper and fluoroplastic washers to which the cable is soldered.
5. The junction of the insulator and the cable must be sealed.
6. We install the antenna on the roof and tighten the insulator nut from the inside of the cabin.
7. We lay the cable from the antenna to the radio under the car trim.
8. We connect the antenna to the radio and check the signal quality. Watch the video on installing the antenna

Sometimes standard antennas installed on cars have low sensitivity, or over time, as a result of mechanical or other damage, they stop working completely. At first, of course, every driver thinks that he doesn’t need this antenna, they say, I’ll listen to CDs, not the radio. But over time, the downloaded music begins to get boring and you want to listen to the banal chatter of DJs on the radio. That’s when the need to purchase an active car antenna arises.

Installation of a radio signal catcher

Installation of an outdoor horizontal antenna begins with the selection of supporting structures. You will subsequently attach insulators to them with your own hands. One of the supports must be installed on the roof of the house. It needs to be reinforced with guy wires. A tree of suitable height can be used as a second support. Insulators can be installed on construction sites using steel cables.

You must attach the outer part of the FM antenna to the insulators with your own hands. It does not need to be subjected to great tension. The wire shrinks if the air temperature is low enough and may lose integrity at low temperatures. Roller blocks will eliminate unnecessary vibrations. To use them, place a small weight on the other end of the wire. It will be connected to the FM antenna if you throw it through the insulator and block.

The receiving part of the antenna must consist of one piece of homogeneous material. If you do not have a homogeneous wire, it is better to construct an FM antenna from separate identical elements. They need to be cleaned and soldered with tin. Equipment for vertical descent of the antenna does not present serious difficulties

Please note that the wire should not be connected to foreign elements. You need to fix the antenna wire with your own hands on a special pull-out stand

This will prevent it from being in the wrong position in windy weather.

If the space for installing an FM antenna with your own hands is limited, you need to use a different design. These are several pieces of wire that look like a “broom”. They will be securely connected by a cable at their lower ends. The ends of the wires can be tightly filled with molten tin. You must cover the soldering area with reliable insulation in the form of bitumen or similar material.

A DIY indoor antenna will be the best option to replace an external catcher. Insulators must be fixed indoors. Their location closer to the ceiling will give an advantage in the quality of signal reception. The wire should be stretched horizontally or rolled into a spiral.

How to make a frame structure?

An aluminum hoop with a diameter of 77 cm and an internal diameter of 1.7 cm can be found in almost any sports store. Plumbing pipes made of a combined metal and plastic structure are well processed. A copper tube with a slightly smaller diameter (16 mm) is also suitable for a radio.

Antenna Rakhmattulaeva

The design of the radio antenna is quite simple.

1. The central core, braid and a short piece of coaxial cable must be soldered to the contacts of the variable capacitor.
2. The other end, the central core and braid, must be soldered to an aluminum hoop. You can also use car clamps, which need to be thoroughly cleaned, with a diameter of 16-26 mm. The contact area also needs to be thoroughly cleaned.
3. The ratio of the frame circumference to the communication loop circumference should be 1:5.
4. From the end of the coaxial cable, as well as from the central core, you need to remove the outer insulation to a length of 1 cm with your own hands.
5. From the middle of the cable for the FM antenna, you need to measure half a centimeter in both directions and remove the outer insulation. After this, the cable braid must be removed. This will lead to its rupture.
6. Check the range of the transceiver device so that the frame has a resonance from 5 to 22 MHz. With other capacitor capacities, you can change the parameters of the transceiver device.
7. If you are more interested in low frequency ranges, it is better to use a frame with a larger diameter - 1 or 1.5 meters. If high-frequency - 0.7 meters.

This solution is a simple option to obtain a resonant antenna capable of operating in many bands. Its radiation pattern will be the figure 8. Antennas made of aluminum and copper work approximately the same.

We have brought to your attention popular types of radio antennas that you can make yourself. Most of these solutions are simple enough to make at home, and their ease of setup will allow you to easily cope with the most complex problems.

Wireless radio waves

When the need for wireless communication arises, an antenna is needed. It has the ability to send or receive electromagnetic waves for communication where a wired system cannot be installed.

The antenna is the key element of this wireless technology. Radio waves are easily created and are widely used for both indoor and outdoor communications due to their ability to pass through buildings and travel long distances.

Key features of transmitting antennas:

1. Since radio transmission is omnidirectional, there is no need for physical matching between the transmitter and receiver.
2. The frequency of radio waves determines many transmission characteristics.
3. At low frequencies, waves can easily pass through obstacles. However, their power decreases with the inverse square of distance.
4. Higher frequency waves are more likely to be absorbed and reflected by obstacles. Due to the long transmission range of radio waves, interference between transmissions is a problem.
5. In the VLF, LF and MF bands, the propagation of waves, also called ground waves, follows the curvature of the Earth.
6. The maximum transmission ranges of these waves are on the order of several hundred kilometers.
7. Transmit antennas are used for low-bandwidth transmissions such as amplitude modulation (AM) radio transmission.
8. HF and VHF transmissions are absorbed by the atmosphere close to the Earth's surface. However, part of the radiation, called the sky wave, travels outward and upward to the ionosphere in the upper atmosphere. The ionosphere contains ionized particles formed by radiation from the Sun. These ionized particles reflect sky waves back to Earth.

DIY technique

Making a radio antenna with your own hands is not that difficult, the main thing is to prepare all the necessary materials and follow the basic rules. A significant increase in the quality and sensitivity of reception is achieved by vertically installing the device under the radio wave propagation range. It takes a craftsman from 30 minutes to 3 hours to make one unit. But to create the structure itself you will need accessible items that can often be found in the garage.

Universal pipe unit

The basis of the design is presented in the form of heating or intra-house water pipes. The final product is extremely strong and durable. For work you need to prepare the following materials and tools:

• High-quality copper or brass foil.
• A special ferrite core taken from a tube TV or a line transformer.
• Durable installation wire up to two meters long and with a cross-section of 0.25 sq. mm.
• Regular PVA glue, as well as adhesive tape.
• To connect the antenna to the receiver itself, you will need fixing pins.

Initially, you need to take the core and make a winding for it. For these purposes, you can use not only electrical tape, but also paper, which must be laid in two even layers. One ball of foil is carefully wound over the paper with a slight overlap of the turn (1 cm). In the overlap area, everything should be isolated to prevent contact between the two sides of the winding. The master must wind 26 turns of wire with bends of 8, 12 and 24 turns onto the preparatory screen. The ends are inserted into the connecting pins. The final configuration of the receiver is carried out according to the scheme for selecting the windings of the communication circuit.

Radio Basics: Real Examples

A baby monitor is about as simple as the resulting radio technology. There is a transmitter that “sits” in the child’s room and a receiver that parents use to listen to their child. Here are some of the important features of a typical baby monitor:

• Modulation : Amplitude Modulation (AM)
• Frequency range : 49 MHz
• Number of frequencies : 1 or 2
• Transmitter power : 0.25 W

A typical baby monitor with a transmitter on the left and a receiver on the right.
The transmitter is located directly in the child’s room and serves as a kind of mini-radio station. Parents take a receiver with them and use it to listen to the child’s actions. Communication range is limited to 200 feet (61 meters) . Don't worry if terms like "modulation" and "frequency" don't make sense to you right now—we'll get to them in a while and I'll explain what they mean.

A mobile phone contains both a receiver and a transmitter, and both operate simultaneously on different frequencies. A cell phone communicates with a cell tower and is capable of transmitting signals over a distance of 2 or 3 miles (3-5 kilometers)

A cell phone is also a radio and is a much more complex device. A cell phone contains both a transmitter and a receiver, and you can use both at the same time—so you'll use hundreds of different frequencies and be able to switch between them automatically. Here are some of the important characteristics of a typical analog cell phone:

• Modulation : Frequency Modulation (FM)
• Frequency range : 800 MHz
• Number of frequencies: 1.664
• Transmitter power : 3 W