What are the main parts of a radio wave transmitter? Antennas: real examples. What is “ham radio communications”

In any broadcast receiver, regardless of its complexity, there are absolutely three elements that ensure its performance. These elements oscillatory circuit, detector and telephones or, if the receiver is with a 34 amplifier, dynamic head direct radiation. Your first receiver, assembled and tested during the previous conversation, consisted of only these three elements. An oscillatory circuit, which included a grounded antenna, provided the receiver with tuning to the wave of the radio station, the detector converted modulated radio frequency oscillations into oscillations audio frequency, which phones converted into sound. Without them, or without any of them, radio reception is impossible. What is the essence of the action of these mandatory elements of a radio receiver?

Oscillatory circuit

The structure of the simplest oscillatory circuit and its diagram are shown in Fig. 38. As you can see, it consists of a coil L and a capacitor C, forming a closed electrical circuit. Under certain conditions, electrical oscillations may arise and exist in the circuit. That is why it is called an oscillatory circuit.

Have you ever observed such a phenomenon: when the power to an electric lighting lamp is turned off, a spark appears between the opening contacts of the switch. If you accidentally connect the terminals of the battery poles of an electric flashlight (which should be avoided), at the moment they are disconnected, a small spark also jumps between them. And in factories, in factory workshops, where switches break electrical circuits through which high currents flow, sparks can be so significant that measures have to be taken to prevent them from causing harm to the person turning on the current. Why do these sparks occur?

From the first conversation, you already know that there is a magnetic field around a current-carrying conductor, which can be depicted in the form of closed magnetic lines of force that penetrate the space surrounding it. This field, if it is constant, can be detected using a magnetic compass needle. If you disconnect a conductor from a current source, then its disappearing magnetic field, dissipating in space, will induce currents in other conductors closest to it. The current is also induced in the conductor that created this magnetic field. And since it is located in the very midst of its own magnetic lines of force, a stronger current will be induced in it than in any other conductor. The direction of this current will be the same as it was at the moment the conductor broke. In other words, a disappearing magnetic field will support the current creating it until it disappears itself, i.e. the energy contained in it is not completely consumed. Consequently, the current flows in the conductor even after the current source is turned off, but, of course, not for long, an insignificant fraction of a second.

But in an open circuit, the movement of electrons is impossible, you will object. Yes, that's true. But after opening the circuit, electric current can flow for some time through the air gap between the disconnected ends of the conductor, between the contacts of a switch or switch. It is this current through the air that forms an electric spark.

This phenomenon is called self-induction, and the electric force (do not confuse it with the phenomenon of induction, familiar to you from the first conversation), which, under the influence of a disappearing magnetic field, maintains a current in it, electromotive force self-induction or, in short, self-induced emf. The greater the self-induction EMF, the more significant the spark can be at the point where the electrical circuit breaks.

The phenomenon of self-induction is observed not only when turning off the current, but also when turning on the current. In the space surrounding the conductor, a magnetic field appears immediately when the current is turned on. At first it is weak, but then it intensifies very quickly. The increasing magnetic field of the current also excites a self-induction current, but this current is directed towards the main current. The self-induction current prevents the instantaneous increase in the main current and the growth of the magnetic field. However, after a short period of time, the main current in the conductor overcomes the counter current of self-induction and reaches its greatest value, the magnetic field becomes constant and the effect of self-induction ceases.

The phenomenon of self-induction can be compared with the phenomenon of inertia. A sled, for example, is difficult to move. But when they pick up speed, stock up on kinetic energy and energy of movement, they cannot be stopped instantly. When braking, the sled continues to slide until the energy stored in it is used up to overcome friction with the snow.

Do all conductors have the same self-inductance? No! The longer the conductor, the greater the self-induction. In a conductor coiled into a coil, the phenomenon of self-induction is more pronounced than in a straight conductor, since the magnetic field of each turn of the coil induces a current not only in this turn, but also in the neighboring turns of this coil. The longer the wire in the coil is, the longer the self-induction current will exist in it after the main current is turned off. Conversely, it will take more time after turning on the main current for the current in the circuit to increase to a certain value and to establish a constant magnetic field strength.

Remember: the property of conductors to influence the current in a circuit when its value changes is called inductance, and the coils in which this property is most strongly manifested are called self-inductance or inductance coils. The greater the number of turns and the size of the coil, the greater its inductance, the more significantly it affects the current in the electrical circuit.

So, the inductor prevents both the increase and decrease of current in the electrical circuit. If it is in a direct current circuit, its influence is felt only when the current is turned on and off. In an alternating current circuit, where the current and its magnetic field are constantly changing, the self-inductive emf of the coil acts all the time the current flows. This is an electrical phenomenon and is used in the first element of the oscillating circuit of the receiver, the inductor.

The second element of the oscillatory circuit of the receiver is a capacitor that stores electrical charges. The simplest capacitor consists of two conductors of electric current, such as two metal plates called capacitor plates, separated by a dielectric, such as air or paper. You have already used such a capacitor during experiments with a simple receiver. The larger the area of ​​the capacitor plates and the closer they are located to each other, the greater the electrical capacitance of this device.

If a direct current source is connected to the plates of the capacitor (Fig. 39, a), then a short-term current will arise in the resulting circuit and the capacitor will be charged to a voltage equal to the voltage of the current source.

You may ask: why does current occur in a circuit where there is a dielectric? When we connect a direct current source to a capacitor, free electrons in the conductors of the resulting circuit begin to move towards the positive pole of the current source, forming a short-term flow of electrons throughout the circuit. As a result, the plate of the capacitor, which is connected to the positive pole of the current source, is depleted of free electrons and is charged positively, and the other plate is enriched in free electrons and, therefore, is charged negatively. Once the capacitor is charged, the short-term current in the circuit, called the capacitor charging current, will stop.

If the current source is disconnected from the capacitor, the capacitor will be charged (Fig. 39.6). The dielectric prevents the transfer of excess electrons from one plate to another. There will be no current between the plates of the capacitor, and the electrical energy accumulated by it will be concentrated in the electric field of the dielectric. But as soon as the plates of a charged capacitor are connected with some kind of conductor (Fig. 39, c), the excess electrons of the negatively charged plate will pass through this conductor to another plate, where they are missing, and the capacitor will be discharged. In this case, a short-term current also arises in the resulting circuit, called the capacitor discharge current. If the capacitance of the capacitor is large and it is charged to a significant voltage, the moment it is discharged is accompanied by the appearance of a significant spark and crackling sound.

The ability of a capacitor to accumulate electric charges and discharged through the conductors connected to it is used in the oscillatory circuit of a radio receiver.

And now, young friend, remember an ordinary swing. You can swing on them in such a way that it will take your breath away. What needs to be done for this? First push to bring the swing out of its resting position, and then apply some force, but only in time with its vibrations. Without much difficulty, you can achieve strong swings of the swing and obtain large amplitudes of vibration. Even a little boy can push an adult on a swing if he applies his strength skillfully. Having rocked the swing harder to achieve larger vibration amplitudes, let’s stop pushing it. What happens next? Due to the stored energy, they swing freely for some time, the amplitude of their oscillations gradually decreases, as they say, the oscillations die out, and finally the swing stops.

With free oscillations of a swing, as well as a freely suspended pendulum, the stored potential energy turns into kinetic energy of motion, which at the highest point again turns into potential, and after a split second again into kinetic. And so on until the entire energy reserve is used up to overcome the friction of the ropes in the places where the swing is suspended and air resistance. With an arbitrarily large supply of energy, free oscillations are always damped: with each oscillation their amplitude decreases and the oscillations gradually die out completely and the swing stops. But the period, i.e. the time during which one oscillation occurs, and therefore the frequency of oscillations remain constant.

However, if the swing is constantly pushed in time with its oscillations and thereby replenishes the loss of energy spent on overcoming various braking forces, the oscillations will become undamped. These are no longer free, but forced vibrations. They will last until the external pushing force ceases to act.

I remembered the swing here because the physical phenomena occurring in such a mechanical oscillatory system are very similar to the phenomena in an electrical oscillatory circuit. In order for electrical oscillations to occur in the circuit, it must be given energy that would push the electrons in it. This can be done by charging, for example, its capacitor.

Let us break the oscillatory circuit with switch S and connect a direct current source to the plates of its capacitor, as shown in Fig. 40 on the left. The capacitor will charge to the battery voltage GB. Then we disconnect the battery from the capacitor, and close the circuit with switch S. The phenomena that will now occur in the circuit are shown graphically in Fig. 40 on the right.

At the moment the circuit is closed by the switch, the upper plate of the capacitor has a positive charge, and the lower plate has a negative charge (Fig. 40, a). At this time (point 0 on the graph) there is no current in the circuit, and all the energy accumulated by the capacitor is concentrated in the electric field of its dielectric. When a capacitor is shorted to the coil, the capacitor will begin to discharge. A current appears in the coil, and a magnetic field surrounds its turns. By the time complete discharge capacitor

(Fig. 40, b), marked on the graph with the number 1, when the voltage on its plates decreases to zero, the current in the coil and the magnetic field energy reach their highest values. It would seem that at this moment the current in the circuit should have stopped. This, however, will not happen, since due to the action of the self-induction EMF, which tends to maintain the current, the movement of electrons in the circuit will continue. But only until all the energy of the magnetic field is used up. At this time, an induced current will flow in the coil, decreasing in value but in the original direction.

By the moment of time marked on the graph by number 2, when the energy of the magnetic field is used up, the capacitor will again be charged, only now there will be a positive charge on its lower plate and a negative charge on the top (Fig. 40, c). Now the electrons will begin to move back in the direction from the top plate through the coil to the bottom plate of the capacitor. By moment 3 (Fig. 40, d) the capacitor will be discharged, and the magnetic field of the coil will reach its greatest value. And again, the self-induction emf will drive electrons along the coil wire, thereby recharging the capacitor.

At time 4 (Fig. 40, e), the state of the electrons in the circuit will be the same as at the initial time 0. One complete oscillation has ended. Naturally, the charged capacitor will again be discharged into the coil, recharged, and the second will happen, followed by the third, fourth, etc. fluctuations. In other words, an alternating electric current, electrical oscillations, will appear in the circuit. But this oscillatory process in the circuit is not endless. It continues until all the energy received by the capacitor from the battery is spent on overcoming the resistance of the circuit coil wire. Oscillations in the circuit are free and, therefore, damped.

What is the frequency of such electron oscillations in the circuit? To understand this issue in more detail, I advise you to carry out such an experiment with a simple pendulum.

Suspend on a thread 100 cm long a ball molded from plasticine, or another load weighing 20 40 g (in Fig. 41, the length of the pendulum is indicated by the Latin letter 1). Take the pendulum out of its equilibrium position and, using a clock with a second hand, count how many complete oscillations it makes in 1 minute. Approximately 30. Therefore, the frequency of oscillation of this pendulum is 0.5 Hz, and the period is 2 s. During the period, the potential energy of the pendulum transforms twice into kinetic energy, and kinetic energy into potential energy. Shorten the thread by half. The frequency of the pendulum will increase by about one and a half times and the period of oscillation will decrease by the same amount.

This experience allows us to conclude: as the length of the pendulum decreases, the frequency of its own oscillations increases, and the period proportionally decreases.

By changing the length of the pendulum suspension, ensure that its oscillation frequency is 1 Hz. This should be with a thread length of about 25 cm. In this case, the period of oscillation of the pendulum will be equal to 1 s. No matter how you try to create the initial swing of the pendulum, the frequency of its oscillations will remain unchanged. But as soon as you shorten or lengthen the thread, the oscillation frequency immediately changes. With the same length of thread there will always be the same oscillation frequency. This is the natural frequency of the pendulum. You can obtain a given oscillation frequency by selecting the length of the thread.

The oscillations of a thread pendulum are damped. They can become undamped only if the pendulum is slightly pushed in time with its oscillations, thus compensating for the energy it expends on overcoming the resistance provided to it by the air, the energy of friction, and gravity.

The natural frequency is also characteristic of an electric oscillatory circuit. It depends, firstly, on the inductance of the coil. The greater the number of turns and the diameter of the coil, the greater its inductance, the longer will be the duration of the period of each oscillation. The natural frequency of oscillations in the circuit will be correspondingly lower. And, conversely, with a decrease in the inductance of the coil, the oscillation period will decrease and the natural frequency of oscillations in the circuit will increase. Secondly, the natural frequency of oscillations in the circuit depends on the capacitance of its capacitor. The larger the capacitance, the more charge the capacitor can accumulate, the longer it will take to recharge it, and the lower the oscillation frequency in the circuit. As the capacitor capacity decreases, the oscillation frequency in the circuit increases. Thus, the natural frequency of damped oscillations in the circuit can be adjusted by changing the inductance of the coil or the capacitance of the capacitor.

But in an electrical circuit, as in a mechanical oscillatory system, it is possible to obtain undamped, i.e. forced oscillations, if at each oscillation the circuit is replenished with additional portions electrical energy from any alternating current source.

How are undamped electrical oscillations excited and maintained in the receiver circuit? Radio frequency oscillations excited in the receiver antenna. These vibrations impart an initial charge to the circuit, and they also support the rhythmic oscillations of electrons in the circuit. But the strongest undamped oscillations in the receiver circuit occur only at the moment of resonance of the circuit’s natural frequency with the frequency of the current in the antenna. How to understand this?

People of the older generation say that in St. Petersburg the Egyptian Bridge collapsed due to soldiers marching in step. And this could happen, apparently, under such circumstances. All the soldiers walked rhythmically along the bridge. As a result, the bridge began to sway and waver. By chance, the bridge's natural vibration frequency coincided with the soldiers' step frequency, and the bridge is said to have gone into resonance. The rhythm of the formation imparted more and more energy to the bridge. As a result, the bridge swayed so much that it collapsed: the coherence of the military formation caused damage to the bridge. If there had been no resonance of the bridge’s natural vibration frequency with the soldiers’ step frequency, nothing would have happened to the bridge. Therefore, by the way, when soldiers pass over weak bridges, it is customary to give the command to knock down a leg.

Here's the experience. Come to some string musical instrument and shout loudly: one of the strings will respond and begin to sound. The one that is in resonance with the frequency of this sound will vibrate more strongly than the other strings and will respond to the sound.

Another experiment with a pendulum. Stretch a thin rope horizontally. Tie the same pendulum made of thread and plasticine to it (Fig. 42). Throw another similar pendulum over the rope, but with a longer thread. The length of the suspension of this pendulum can be changed by pulling the free end of the thread with your hand. Set the pendulum into oscillatory motion. In this case, the first pendulum will also begin to oscillate, but with a smaller amplitude. Without stopping the oscillations of the second pendulum, gradually reduce the length of its suspension; the amplitude of oscillations of the first pendulum will increase. In this experiment, illustrating the resonance of mechanical vibrations, the first pendulum is a receiver of vibrations excited by the second pendulum. The reason that forces the first pendulum to oscillate is the periodic oscillations of the tension rod with a frequency equal to the oscillation frequency of the second pendulum. The forced oscillations of the first pendulum will have maximum amplitude only when its natural frequency coincides with the oscillation frequency of the second.

Such or similar phenomena, only, of course, of electrical origin, are also observed in the oscillatory circuit of the receiver. From the action of waves from many radio stations, currents of various frequencies are excited in the receiving antenna. From all the oscillations of radio frequencies, we need to select only the carrier frequency of the radio station whose broadcasts we want to listen to. To do this, we must select the number of coil turns and the capacitance of the oscillating circuit capacitor so that its natural frequency coincides with the frequency of the current created in the antenna by the radio waves of the station of interest to us. In this case, the strongest oscillations will occur in the circuit with the carrier frequency of the radio station to which it is tuned. This is the setting of the receiver circuit in resonance with the frequency of the transmitting station. In this case, the signals of other stations are not heard at all or are heard very quietly, since the oscillations they excite in the circuit will be many times weaker.

Thus, by tuning the circuit of your first receiver into resonance with the carrier frequency of the radio station, you, with its help, sort of selected and isolated the frequency oscillations of only this station. The better the circuit isolates the necessary vibrations from the antenna, the higher the selectivity of the receiver, the weaker the interference from other radio stations will be.

So far I have told you about a closed oscillatory circuit, i.e. circuit, the natural frequency of which is determined only by the inductance of the coil and the capacitance of the capacitor that forms it. However, the receiver input circuit also includes an antenna and ground. This is no longer a closed, but an open oscillatory circuit. The fact is that the antenna wire and ground are the plates of a capacitor (Fig. 43), which has some electrical capacitance. Depending on the length of the wire and the height of the antenna above the ground, this capacitance can be several hundred picofarads. Such a capacitor in Fig. 34, but was shown with dashed lines. But the antenna and the ground can also be considered as an incomplete turn of a large coil. Therefore, the antenna and grounding, taken together, also have inductance. And capacitance together with inductance form an oscillatory circuit.

Such a circuit, which is an open oscillatory circuit, also has its own oscillation frequency. By connecting inductors and capacitors between the antenna and the ground, we can change its natural frequency, tune it into resonance with the frequencies of different radio stations. You already know how this is done in practice.

I will not be mistaken if I say that the oscillatory circuit is the heart of the radio receiver. And not just a radio. You will be convinced of this later. That's why I paid a lot of attention to him.

I move on to the second element of the receiver, the detector.

For a long time, radios topped the list of the most significant inventions of mankind. The first such devices have now been reconstructed and changed in a modern way, but little has changed in their assembly circuit - the same antenna, the same grounding and an oscillating circuit for filtering out unnecessary signals. Undoubtedly, circuits have become much more complicated since the time of the creator of radio, Popov. His followers developed transistors and microcircuits to reproduce a higher quality and energy-consuming signal.

Why is it better to start with simple circuits?

If you understand the simple one, you can be sure that most of the path to success in the field of assembly and operation has already been mastered. In this article we will analyze several circuits of such devices, the history of their origin and the main characteristics: frequency, range, etc.

Historical background

May 7, 1895 is considered the birthday of the radio receiver. On this day, the Russian scientist A.S. Popov demonstrated his apparatus at a meeting of the Russian Physicochemical Society.

In 1899, the first radio communication line, 45 km long, was built between and the city of Kotka. During World War I, direct amplification receivers and vacuum tubes became widespread. During hostilities, the presence of a radio turned out to be strategically necessary.

In 1918, simultaneously in France, Germany and the USA, scientists L. Levvy, L. Schottky and E. Armstrong developed the superheterodyne reception method, but due to weak vacuum tubes This principle became widespread only in the 1930s.

Transistor devices emerged and developed in the 50s and 60s. The first widely used four-transistor radio, the Regency TR-1, was created by German physicist Herbert Mathare with the support of industrialist Jakob Michael. It went on sale in the US in 1954. All old radios used transistors.

In the 70s, the study and implementation of integrated circuits began. Receivers are now being developed through large integration of nodes and digital processing signals.

Device characteristics

Both old and modern radios have certain characteristics:

1. Sensitivity is the ability to receive weak signals.
2. Dynamic range - measured in Hertz.
3. Noise immunity.
4. Selectivity (selectivity) - the ability to suppress extraneous signals.
5. Self-noise level.
6. Stability.

These characteristics do not change in new generations of receivers and determine their performance and ease of use.

The principle of operation of radio receivers

In the most general form, USSR radio receivers worked according to the following scheme:

1. Due to fluctuations in the electromagnetic field, alternating current appears in the antenna.
2. The oscillations are filtered (selectivity) to separate information from noise, i.e., the important component of the signal is isolated.
3. The received signal is converted into sound (in the case of radio receivers).

Using a similar principle, an image appears on a TV, digital data is transmitted, and radio-controlled equipment (children’s helicopters, cars) operates.

The first receiver was more like a glass tube with two electrodes and sawdust inside. The work was carried out according to the principle of the action of charges on metal powder. The receiver had a huge resistance by modern standards (up to 1000 Ohms) due to the fact that the sawdust had poor contact with each other, and part of the charge slipped into the air space, where it was dissipated. Over time, these filings were replaced by an oscillating circuit and transistors to store and transmit energy.

Depending on the individual receiver circuit, the signal in it may undergo additional amplitude and frequency filtering, amplification, digitization for further software processing, etc. A simple radio receiver circuit provides for single signal processing.

Terminology

An oscillating circuit in its simplest form is a coil and a capacitor closed in a circuit. With their help, you can select the one you need from all the incoming signals due to the circuit’s own frequency of oscillation. USSR radios, as well as modern devices, are based on this segment. How does it all work?

As a rule, radio receivers are powered by batteries, the number of which varies from 1 to 9. For transistor devices, 7D-0.1 and Krona type batteries with a voltage of up to 9 V are widely used. The more batteries a simple radio receiver circuit requires, the longer it will work .

Based on the frequency of received signals, devices are divided into the following types:

1. Long-wave (LW) - from 150 to 450 kHz (easily scattered in the ionosphere). What matters are ground waves, the intensity of which decreases with distance.
2. Medium wave (MV) - from 500 to 1500 kHz (easily scattered in the ionosphere during the day, but reflected at night). During daylight hours, the radius of action is determined by grounded waves, at night - by reflected ones.
3. Shortwave (HF) - from 3 to 30 MHz (do not land, are exclusively reflected by the ionosphere, so there is a radio silence zone around the receiver). With low transmitter power, short waves can travel long distances.
4. Ultrashortwave (UHF) - from 30 to 300 MHz (have a high penetrating ability, are usually reflected by the ionosphere and easily bend around obstacles).
5. - from 300 MHz to 3 GHz (used in cellular communications and Wi-Fi, operate within visual range, do not bend around obstacles and propagate in a straight line).
6. Extremely high frequency (EHF) - from 3 to 30 GHz (used for satellite communications, reflected from obstacles and operating within line of sight).
7. Hyper-high frequency (HHF) - from 30 GHz to 300 GHz (they do not bend around obstacles and are reflected like light, they are used extremely limited).

When using HF, MF and DV radio broadcasting can be carried out while being far from the station. The VHF band receives signals more specifically, but if a station only supports it, then you won’t be able to listen on other frequencies. The receiver can be equipped with a player for listening to music, a projector for displaying on remote surfaces, a clock and an alarm clock. The description of the radio receiver circuit with such additions will become more complicated.

The introduction of microcircuits into radio receivers made it possible to significantly increase the reception radius and frequency of signals. Their main advantage is their relatively low energy consumption and small size, which is convenient for portability. The microcircuit contains all the necessary parameters for downsampling the signal and making the output data easier to read. Digital signal processing dominates modern devices. were intended only for transmitting an audio signal, only in recent decades the design of receivers has developed and become more complex.

Circuits of the simplest receivers

The circuit of the simplest radio receiver for assembling a house was developed back in Soviet times. Then, as now, devices were divided into detector, direct amplification, direct conversion, superheterodyne, reflex, regenerative and super-regenerative. Detector receivers are considered the simplest to understand and assemble, from which the development of radio can be considered to have begun at the beginning of the 20th century. The most difficult devices to build were those based on microcircuits and several transistors. However, once you understand one pattern, others will no longer pose a problem.

Simple detector receiver

The circuit of the simplest radio receiver contains two parts: a germanium diode (D8 and D9 are suitable) and a main telephone with high resistance (TON1 or TON2). Since there is no oscillatory circuit in the circuit, it will not be able to catch signals from a specific radio station broadcast in a given area, but it will cope with its main task.

For work you will need good antenna, which can be thrown onto a tree, and a ground wire. To be sure, it is enough to attach it to a massive piece of metal (for example, to a bucket) and bury it a few centimeters into the ground.

Option with oscillating circuit

To introduce selectivity, you can add an inductor and a capacitor to the previous circuit, creating an oscillating circuit. Now, if you wish, you can catch the signal of a specific radio station and even amplify it.

Tube regenerative shortwave receiver

Tube radio receivers, the circuit of which is quite simple, are made to receive signals from amateur stations at short distances - in the ranges from VHF (ultra-short wave) to LW (long wave). Finger battery lamps work on this circuit. They generate best on VHF. And the resistance of the anode load is removed by low frequency. All details are shown in the diagram; only the coils and inductor can be considered homemade. If you want to receive television signals, then the L2 coil (EBF11) is made up of 7 turns with a diameter of 15 mm and a 1.5 mm wire. 5 turns are suitable.

Direct amplification radio receiver with two transistors

The circuit also contains a two-stage low-frequency amplifier - this is a tunable input oscillatory circuit of the radio receiver. The first stage is an RF modulated signal detector. The inductor is wound in 80 turns with PEV-0.25 wire (from the sixth turn there is a tap from below according to the diagram) on a ferrite rod with a diameter of 10 mm and a length of 40.

This simple radio receiver circuit is designed to recognize powerful signals from nearby stations.

Supergenerative device for FM bands

The FM receiver, assembled according to E. Solodovnikov’s model, is easy to assemble, but has high sensitivity (up to 1 µV). Such devices are used for high-frequency signals (more than 1 MHz) with amplitude modulation. Thanks to the strong positive feedback the coefficient increases to infinity, and the circuit goes into generation mode. For this reason, self-excitation occurs. To avoid it and use the receiver as a high-frequency amplifier, set the coefficient level and, when it reaches this value, sharply reduce it to a minimum. For continuous gain monitoring, you can use a sawtooth pulse generator, or you can do it simpler.

In practice, the amplifier itself often acts as a generator. Using filters (R6C7) that highlight signals low frequencies, the passage of ultrasonic vibrations to the input of the subsequent ULF cascade is limited. For FM signals 100-108 MHz, coil L1 is converted into a half-turn with a cross-section of 30 mm and a linear part of 20 mm with a wire diameter of 1 mm. And coil L2 contains 2-3 turns with a diameter of 15 mm and a wire with a cross-section of 0.7 mm inside a half-turn. Receiver amplification is possible for signals from 87.5 MHz.

Device on a chip

The HF radio receiver, whose circuit was developed in the 70s, is now considered the prototype of the Internet. Shortwave signals (3-30 MHz) travel great distances. It is not difficult to set up a receiver to listen to broadcasts in another country. For this, the prototype received the name world radio.

Simple HF receiver

A simpler radio receiver circuit lacks a microcircuit. Covers the range from 4 to 13 MHz in frequency and up to 75 meters in length. Power supply - 9 V from the Krona battery. The installation wire can serve as an antenna. The receiver works with headphones from the player. The high-frequency treatise is built on transistors VT1 and VT2. Due to capacitor C3, a positive reverse charge arises, regulated by resistor R5.

Modern radios

Modern devices are very similar to radio receivers in the USSR: they use the same antenna, which produces weak electromagnetic oscillations. High-frequency vibrations from different radio stations appear in the antenna. They are not used directly to transmit a signal, but carry out the operation of the subsequent circuit. Now this effect is achieved using semiconductor devices.

Receivers were widely developed in the mid-20th century and have been continuously improving since then, despite their replacement by mobile phones, tablets and televisions.

The general design of radio receivers has changed slightly since Popov's time. We can say that the circuits have become much more complicated, microcircuits and transistors have been added, and it has become possible to receive not only an audio signal, but also to build in a projector. This is how receivers evolved into televisions. Now, if you wish, you can build whatever your heart desires into the device.

RADIO EQUIPMENT

AIRCRAFT

(Diamond DA 40 NG AIRCRAFT)

TUTORIAL

Compiled by: Zadorozhny V.I.

Savchuk N.A.

Buguruslan

General concepts about radio communications.

Radio communication is carried out using radio stations. Radio communications are based on the principle of radiating electromagnetic energy into space in the form of radio waves.

Electromagnetic energy of radio waves is the energy of alternating currents of very high frequency, on the order of millions or more cycles per second. Electromagnetic energy from radio waves is generated by the radio transmitter and radiated into space by the transmitting antenna. Electromagnetic energy emitted from the transmission point at an enormous speed equal to the speed of light (300,000 km/sec) spreads in space and at the reception point is received by another radio station, consisting of an antenna and a radio receiver.

Any transmitting and receiving radio station must include a receiver and a radio transmitter.

The main purpose of the transmitter is to generate high-frequency alternating currents that should power the transmitting antenna. The generation of high frequency currents in the transmitter is achieved by converting direct current energy into oscillations of high frequency currents.

The transmitter generator generates sinusoidal and constant amplitude high frequency currents. To transmit information, these vibrations are modulated either by radiotelegraph alphabet or by voice. The first type of radio transmission is called radiotelegraphy, and the second - radiotelephony.

During radiotelegraph operation, electromagnetic energy is not radiated into space continuously, but in the form of series of oscillations of varying durations, but with the same amplitude (at the carrier frequency); series of vibrations correspond to the radiotelegraph alphabet code (Fig. 1). In this case, the oscillations are controlled using an ordinary radiotelegraph key.

During radiotelephone operation, on the contrary, the antenna is continuously fed with high-frequency current, but the current itself constantly changes in magnitude (oscillations modulated in amplitude) in time with the frequency of the sound vibrations of the operator’s voice (Fig. 2). In this case, the vibrations are controlled through a microphone (laryngophone) - a device that converts sound vibrations (mechanical vibrations of the membrane) into electrical vibrations of low audio frequency.

In addition to the transmitter, any transmitting and receiving radio station includes as a mandatory element an antenna system consisting of the antennas And counterweight. Antenna system is a device that emits electromagnetic energy during transmission and captures and receives it from space during reception. The antenna is either a single wire or a system of wires raised above the ground or above the airframe and insulated at the upper end. The plane's body itself serves as a counterweight. On ultrashort waves (VHF), the antenna of an aircraft radio station is most often a thick knife-shaped rod.

The design and principle of operation of radio transmitters.

The design and principle of operation of radio receivers.

The principle of radiotelephone modulation.

Information about antennas and electromagnetic energy radiation.

Antennas.

An antenna is a necessary part of any radio transmitting and receiving device. Using feeders, the transmitting antenna is connected to the radio transmitter, and the receiving antenna is connected to the radio receiver. Free electromagnetic waves propagate between the antennas. Radio waves in space are scattered and absorbed by the environment. To reduce losses, they are concentrated in certain directions.

The transmitting antenna is designed to convert radio signal energy into free electromagnetic waves emitted in given directions.

The receiving antenna is designed to convert electromagnetic waves coming from certain directions into radio signal energy, which takes the form of coupled electromagnetic waves.

Thus, reversible processes occur in the receiving and transmitting antennas. Sometimes one antenna is used for reception and transmission, which is of great importance in practice.

Oscillations are emitted by an open oscillatory circuit, which can be formed from a closed one by moving the capacitor plates apart and simultaneously increasing their size to maintain a constant natural frequency.

In practice, asymmetrical vibrators are widely used, in which the ground replaces the second wire of the symmetrical vibrator. This is possible due to the good conductivity of the earth.

If the antenna is directional, then the radiation power flux density of such an antenna in different directions is different. The directional properties of an antenna are judged by its radiation pattern- dependence of the radiation field strength on the direction when measuring this field at the same distance from the antenna, i.e. it shows the shape of the radio field of a given antenna.

The antennas are subject to the following operational requirements: operational safety, high mechanical strength and reliability, minimum dimensions; and weight, low cost, etc.

The operating conditions for aircraft antennas are specific. Their protruding parts create aerodynamic drag. If the antenna is poorly directed, then it irradiates the fuselage of the aircraft, as a result of which the n diagram is distorted.

Types of aircraft antennas.

Modern aircraft are equipped rigid antenna devices. The same antenna is used for reception and transmission. When the aircraft radio station is operating for transmission, the antenna is connected to the transmitter via a special antenna relay, and when the station is operating for reception, it is connected to the receiver.

Figure 7 shows a rigid L-shaped short-wave antenna of an all-metal aircraft for long distance radio stations. It is made of copper wire.

Fig.8. General view of an aircraft ultrashort wave antenna

The AShS-I type whip antenna has a streamlined shape and is inclined towards the fuselage surface to reduce aerodynamic drag. This antenna is used in command radio stations on meter and decimeter waves and in automatic radio compass, operating in the mid-wave range.

Job automatic radio compass provides whip and loop antennas. In the simplest case, a loop antenna is a flat coil of rectangular wire. The axis of rotation 00" coincides with the axis of symmetry of the frame.

Fig.9. Loop antenna and radiation pattern

The frame in the horizontal plane has directional properties: its radiation pattern has the shape of a figure eight (Fig. 9).

In the direction perpendicular to the plane of the frame, there is no difference in the path of the waves to its opposite vertical wires, so there will be no reception. The greatest difference in the path of water and the amplitude of the resulting emf. will be at y = 0° and y = 180°.

The actual frame height is significantly less than the geometric height. Therefore, the frame has low radiation resistance and efficiency; it is used only as a receiving antenna. Rotating the frame until the maximum emf is obtained in it. set the direction to the radio station.

The minimum of the diagram is sharper than the maximum, so the loop antenna is often used to find direction using the minimum reception.

Magnetic antennas are a type of loop antenna. Such antennas have a core with high magnetic permeability (ferrite).

IN radio altimeter The same type of half-wave vibrator antennas are used: one of them is transmitting, and the other is receiving. The vibrator itself consists of two metal tubes, isolated from each other by a ring made of radio porcelain. The antennas are mounted under the fuselage of the aircraft at a distance sufficient to weaken the mutual influence of the antennas.

Grounding and counterbalance.

It makes sense to ground one half of the antenna if the soil serves good guide. Sea water and damp soil have fairly good conductivity. Dry soil and sand have poor conductivity, resulting in large energy losses during radio operation. In this case, you need to arrange grounding by burying a conductor or several conductors in the ground. Grounding in radio stations serves as one of the plates of the antenna-ground “capacitor”. In addition, electrical charges that arise in the antenna due to electrification by dry snow, dust, or during a thunderstorm are discharged into the ground.

On hard ground, on mobile radio stations and on airplanes, counterweights are used. The counterweight consists of several wires that are suspended under the antenna not high above the ground. The power lines of the antenna's electric field are closed to the counterweight, isolated from the ground.

The ideal counterweight should be a large metal area above the ground. In this case, the counterweight should represent a continuous screen for the electromagnetic field and thereby minimize energy losses in the ground. However, performing such a counterbalance is practically difficult. Sometimes a metal radio body is used as a counterweight. The metal fuselage serves as a counterweight for aircraft radios. But the distribution of currents in the fuselage differs from their distribution in the counterweight. In this regard, the spatial distribution of the electromagnetic field and the directional propagation of radio waves change.

Metallization.

Metallization is understood as a reliable electrical connection of all metal parts of the aircraft and parts of its equipment between themselves and the aircraft body. The presence of metallization provides:

1. Creation of a continuous negative wire, since the negative of the on-board network is “grounded” to the aircraft body.

2. Leveling the potential of static electricity that occurs on aircraft parts and parts in flight.

3. Creation of an effective counterweight for transmitting devices of radio stations.

4. Reducing interference to radio reception and increasing the fire safety of the aircraft.

On the plane, the aircraft controls, aircraft engine and its frame, oil and fuel systems, instrument panels, electrical equipment, units and shielded cables of radio equipment are metallized.

The metallization of removable and movable components and assemblies is made of flexible jumpers made of tinned copper braiding, the ends of which are embedded in tips.

Ionosphere and its properties.

Under the influence of the rays of the Sun, cosmic rays and other factors, the air is ionized, i.e. Some of the gas atoms that make up the air disintegrate into free electrons and positive ions. Ionized air has a strong effect on the propagation of radio waves.

For different gases, the maximum ionization occurs at different heights. Ionized layer of the atmosphere - ionosphere- consists of several layers.

At an altitude of 60...80 km there is a layer D, existing only during the day. The next layer E is located at an altitude of 90... 130 km. Even higher is layer F, which has a height of 250...350 km at night, and during the day it is divided into two layers: F 1 - at an altitude of 180...220 km and F 2 - at an altitude of 220...500 km.

The height, thickness and conductivity of the ionized layers are different in different times days and years due to changes in the ionizing effect of sunlight. The greater the ionizing effect of solar rays, the greater the conductivity and thickness of the ionized layers and the lower they are located. During the day, their conductivity and thickness are greater, and their height above the ground is less than at night. In summer, the conductivity and thickness of the ionospheric layers are greater, and the height is lower than in winter. Every 11 years, the Sun repeats a maximum of sunspots, which are powerful sources of ionizing radiation. At this time, the conductivity and thickness of the ionized layers reach a maximum, and they are located lower.

Internal and external communication systems.

A Garmin GMA 1347 digital audio panel is installed on the pilots’ dashboard between the PFD and MFD indicators. It is an integral part of the Garmin G 1000 complex, connected to the integrated GIA 63 avionics units via the RS-232 digital data exchange protocol and is intended for:

Internal communication (Intercom) for crew members and passengers through aircraft headsets with automatic “receive/transmit” switching, manual volume control and noise reduction;

External simplex, non-search and non-tuning radio communication through two VHF radio stations COM 1 and/or COM 2 and pilots’ headsets;

Repeated playback of a recording audio information from the outputs of radio stations COM 1 or COM 2;

To listen to the identification signals of one of the ground VOR, DME, NDB (localization radio stations) or LOC localizer of the ILS landing system at the choice of the pilots;

Listening to signals from marker beacons of landing systems or route marker beacons (practically not used) without the choice of pilots. For most Russian airfields, the passage of a distant beacon is accompanied by the sound of an intermittent tone with a frequency of 3000 Hz in the form of a series of two dashes per second, and the passage of a near one - in the form of a series of six dots per second;

Broadcasting sound signals of selected equipment through the cabin loudspeaker with its muting while the microphones are turned on during radio communication;

Manually switching on the mode of combined display of aerobatic and other important information on a working display if one of the PFD or MFD indicators fails.

The cockpit loudspeaker, as well as the microphones and headsets of the pilots and two passengers, are connected to the audio panel. The loudspeaker is located on the cabin ceiling above the passenger seats. The sockets for connecting the connectors of four aircraft headsets are located on the back of the central console between the pilots’ seats.

To connect the microphones of the aircraft headsets of both pilots to radio transmitters during radio communication, as well as when notifying passengers, PTT buttons (Push-To-Talk - an analogue of the “Radio” button) are located on the pilots’ control handles.

The following controls are located on the front of the audio panel:

- COM 1 MIC - key for selecting radio station COM 1, through which you can receive and transmit speech information from the aircraft headset microphone when you press the PTT button on the control stick of one of the pilots;

- COM 2 MIC - key for selecting radio station COM 2, through which you can receive and transmit voice information from the aircraft headset microphone when you press the PTT button on the control stick of one of the pilots;

- COM 3 MIC - key not activated;

- COM 1 - key for selecting radio station COM 1 only for listening to messages received through it;

COM 2 - key for selecting radio station COM 2 only for listening to messages received through it;

- COM 3- the key is not activated;

- COM 1/2- a key, after pressing which the 1st and 2nd pilots can simultaneously and independently conduct radio communication, with the 1st pilot through the radio station COM 1, and the 2nd - through COM 2. In addition, the 1st pilot can also listen identification signals of selected radio beacons, while the 2nd pilot - only voice messages received by radio station COM 2;

TEL - key not activated;

RA - a key for addressing passengers when pressing the PTT button on the control stick of one of the pilots. If the COM 1/2 key is pressed, then only the 2nd pilot can address passengers through the cabin loudspeaker;

SPKR - key for connecting a cabin loudspeaker. Through it, signals from selected radio equipment are broadcast, as well as signals that are issued regardless of the choice of the crew. When you turn on the microphones for transmission using the PTT button, the loudspeaker sound is muted;

MKR/MUTE - a key that allows you to temporarily disable listening to signals from an overflight marker beacon in cases where, for example, they interfere with receiving information from the air traffic controller. In this case, pilots observe the marker beacon signal on the PFD display. In addition, the key allows you to interrupt listening to the dispatcher's recorded speech signals;

AUX - the key is not activated. It can be used when installing additional (Auxiliary) navigation aids on an aircraft;

DME, NAV 1, NAV 2, ADF - keys that, when pressed, allow you to select the appropriate radio beacons for listening in order to identify them or receive messages broadcast through them (for example, emergency transmissions from the dispatcher through a long-range radio beacon);

MAN SQ - a key that, when pressed, switches the PILOT-0-PASS knobs from the listening volume adjustment mode to the Manually adjustment mode of the noise suppressor (Squelch);

- PLAY- key for repeat playback of recorded digital form audio messages, for example, from an air traffic controller in cases where they were not perceived by the crew the first time;

- PILOT And COPLT- keys used for switching intra-aircraft communications. Depending on the combination of activation of these keys, four modes of intra-aircraft communication are possible:

Only the key is included PILOT- The 1st pilot is isolated and can only listen to selected radios, the 2nd pilot and passengers can communicate with each other.

Only the key is included COPLT- The 2nd pilot is isolated, the 1st pilot and passengers can listen to selected radios and communicate with each other.

Both keys PILOT And COPLT included - the 1st and 2nd pilots are isolated from the passengers, fats, can communicate with each other and listen to selected radios. Passengers can only communicate with each other.

Both PILOT and COPLT keys are turned off - both passengers and pilots can communicate and listen to selected radios;

- PILOT-0-PASS- double knobs for adjusting the listening volume by the 1st pilot (internal) and the 2nd pilot and passengers (external). At the same time, the inscription VOL is highlighted to the left and below the handles. When the MAN SQ key is turned on, these knobs also allow you to adjust the level of the noise suppressor. At the same time, the inscription SQ is highlighted to the right and below the handles. Switching between VOL and SQ modes in this case is done by successively pressing the internal small knob-button;

DISPLAY BACKUP - button for switching the PFD and MFD display indications to a combined mode if one of them fails. The button must also be pressed when automatically switching to the combined indication mode when the faulty indicator blinks.

When you press the keys on the audio panel and turn on the corresponding mode, the indicator in the form of a white triangle above the key starts to light (see Fig. 2.15).

The audio panel receives 28 V DC power from the avionics AVIONIC BUS with protection through a 5 A AUDIO circuit breaker.

When the audio panel is turned on, as well as during operation, it performs self-testing. When failures are detected, a corresponding message appears in the notification message window " ALERTS» on the PFD display. A list of messages regarding the audio panel and associated equipment is shown in Table 1. When such messages appear, equipment maintenance is required.

Table1.

Taking off with a faulty audio panel is prohibited. Under the dashboard on the left there is a connector for connecting an additional microphone. Together with the loudspeaker, it can be used by the left pilot instead of an aircraft headset. Radio stations COM 1 and COM 2 are an integral part of the integrated Garmin G 1000 complex, built into G1A 63 avionics units and designed for:

Simplex untuned command radio communication in the VHF radio wave range. Two-way aviation air communication is carried out with air traffic controllers, with the crews of other aircraft or dispatchers of production services of airline enterprises;

Listening to messages from aerodrome auxiliary services, such as ATIS, weather services VOLMET, SIGMET, etc.;

Radio communications on the international emergency frequency 121.500 MHz, for example during search and rescue operations.

In addition to the transceiver equipment integrated into the GIA 63 units, both radio stations include “receive-transmit” switches - PTT buttons installed on the pilot’s control sticks and whip antennas (the antenna of the COM 2 radio station is L-shaped). The placement of radio station antennas and their appearance are shown in Fig. 1.

Rice. 1. Appearance of VHF radio station antennas:

a - antenna of radio station COM 1; b - antenna of radio station COM 2

Radio stations COM 1 and COM 2 are identical and are characterized by the following main operational and technical indicators:

Operating frequency range, MHz 118,000-136,975

Frequency grid step, kHz 25 or 8.33 (crew choice)

Type of modulation amplitude (AM)

Average power transmitter, W 16

Power supply voltage, V 28 DC

Range, km 120 -130 at flight altitude 1000 m

Receiver sensitivity, µV 2.5

The selection of the frequency grid step (CHANNEL SPACING) is carried out by the crew on the fourth page “AUX-SYSTEM SETUP” of the “AUX” group on the MFD display in the “COM CONFIG” section using the knobs FMS.

The radio station COM1 receives power supply with direct current voltage of 28 V from the left main bus LH MAIN BUS with protection through a circuit breaker COM 1 with a rating of 5A, and the radio station COM 2 - from the avionics bus AVIONIC BUS through a circuit breaker COM rated also 5 A.

Radio stations do not have their own control panels. All radio controls and tuning indicators are located in the upper right part of each of the displays - PFD and MFD (Fig. 2.). The operation of these controls and setting indicators is the same regardless of which display they are used by the crew on.

Rice. 2 Top right of PFD and MFD displays

Tuning radio stations can be done either manually or from the aeronautical database. Information on the frequencies of ground radio stations for air traffic control operating in certain airspace zones is taken from the updated aeronautical database. For example, on the MFD, using the FMS knobs in the “WPT” page group, the first page “WPT-AIRPORT INFORMATION” is selected. Then in the “FREQUENCIES” section the frequency of the desired ATC sector is selected. The selection is confirmed by pressing the ENT key. After this, the frequency value appears in the window of prepared frequencies of the radio station being tuned. Likewise accelerated setup radio stations in emergency situations is possible from the database of nearby airfields (NEAREST AIRPORTS).

Manual tuning of radio stations is carried out using dual COM knobs, with the small inner knob setting the frequency values ​​in kHz, and the large outer knob setting the frequency values ​​in MHz. The blue frame, the color of the numbers and the “ ” symbol between the active and prepared frequencies indicate which radio station is being tuned. Switching between radio stations COM 1 and COM 2 to configure and control them is done by pressing the small internal knob-button COM (back by pressing again). Radio stations selected by pressing the COM MIC and/or COM keys on the audio panel for radio communication and/or listening are represented by the value of their operating frequencies in green (COM 1 in Fig. 2.17). Switching between operating frequency and prepared frequency indicated blue and frame, is done by pressing the “ ” (Transfer) key. A long (about 2 s) press on this key transfers the operating frequency to the area indicated by the blue frame, i.e., to the prepared one, and the radio station is tuned to the international emergency frequency of 121.500 MHz.

The level of the received signal (volume) is set with the VOL knob for the radio station that is selected with the small internal COM knob-button for tuning and control. Rotating the VOL knob changes the signal level from 0 to 100%. The variable level value in percentage with the word “VOLUME” is displayed instead of the prepared frequency values ​​without a frame. The display continues for three seconds after the VOL knob has been rotated. This knob is also a button that, when pressed, turns on automatic noise suppression (Squelch) in the receiver of the radio station selected for tuning. The noise suppressor is turned off by pressing again.

When receiving messages on the operating frequency of the selected radio station, the letters RX appear next to the displayed frequency value, and when transmitting, the letters TX appear.

Monitoring the performance of radio stations is carried out by the crew by self-listening in aircraft headsets when accessing external radio communications. The failure of radio stations is also detected by the absence of listening to messages during reception.

In addition, when the radio stations are turned on and during operation, they perform self-testing. When failures are detected, a red crosshair appears instead of the digital frequencies of the failed radio. In addition, a corresponding message appears in the ALERTS message window on the PFD display.

The list of messages relating to radio stations COM 1, COM 2 and associated equipment is given in Table 2. When such messages appear, equipment maintenance is required. Table 2.

If the audio panel or digital audio signal processing units fail, the COM 1 radio operates without digital signal processing and is connected directly to the 1st pilot’s aviation headset.

Before the flight, when inspecting the aircraft, it is necessary to check the integrity of the antennas. the presence of ice and dirt on them. Flight with a faulty radio station is prohibited. The failure of both radio stations in flight corresponds to the emergency situation “Radio communication failure”. In this case, it is necessary to set the ATC transponder code (Squawk) to 7600 to inform the air traffic controller about a radio failure.

Automatic radio compass.

Purpose: 1) Defines CUR;

2) Automatic radio compass KR 87 designed to solve

the following navigation tasks:

Flying to and from a radio station with visual indication

heading angle;

Landing approach together with other instruments according to the support system

blind landing;

Automatic and continuous detection and visual

indication of the heading angle of the radio station ( CUR) ranging from 0° to 360°;

Auditory reception of call signs from radio stations operating in the frequency range of the radio compass.

O.T.D.: 1) U power = 28V; 2) f p = 200-1799 kHz; 3) ΔKUR = ±3º; 4) D = 160-180 km;

Composition and 1) Receiver;

accommodation: 2) Radio compass antenna – at the bottom of the fuselage;

3) Indicator;

Peculiarities

SW propagation:

NE spread near the surface of the earth depending on the time of day as follows: a) At night - with two surface rays (1) and spatial (2) reflected from the upper layers of the ionosphere E, F;

b) During the day - only superficial (1) , because the spatial beam is absorbed by the lower layer of the ionosphere D.

Therefore the range ARK depends on time of day and power PRS.

Operating modes

and operating principle: ARK has 2 operating mode:

Controls

and control:

Index KI 227.

Instrument front panel KI 227

Automatic radio compass KR 87 has two operating modes;

Mode ANT(antenna),

Mode ADF(compass),

In mode ANT The direction finder is turned off, the loop antenna is blocked, the device works as a receiver, allowing the reception of beacon sound signals through a loudspeaker or headphones.

This mode provides clearer reception of audio signals and is used to identify the radio station.

In various regions of the world, some stations operating on low medium frequencies use the telegraph transmission system for identification purposes. These stations are easily identified using a button BFO. When the button is pressed BFO signal in 1000Hz becomes audible as soon as a high-frequency radio signal appears on the selected frequency. Message BFO appears in the center of the display.

Switch to mode ADF carried out by pressing a button ADF, and the display on the left will show the inscription ADF. On the device KI 227 arrow CUR will show the heading angle of the radio station.

The indicator on the left shows the operating (active) frequency, on the right - the standby (standby) frequency or time.

If the radio compass displays the time, then to indicate the duty frequency you need to press the button FRQ.

Setting up ARC

On the PFD, press the “ADF/DME” soft button, the “ADF/DME TUNING” window will open;

Press FMS, the preparation frequency will be displayed in the ADF window;

Using the large and small FMS knobs, dial the drive frequency;

Press ENT 2 times to transfer the dialed frequency to the working one;

Press the PFD program button, it will open additional buttons"BRG-1", "BRG-2";

Press “BRG-1”, “BRG-2” until the ADF operating mode is displayed in the window and the drive frequency is displayed.

Depending on whether “BRG-1” or “BRG-2” is pressed, single or double blue arrows will point to the selected drive.

Operation. 1) Listening ARK KR-87 carried out by pressing a button ADF on GMA-340.

2) Mode "antenna"- for listening only. CUR on

KI 227 in this mode shows 90°, left on the panel

KR-87 the inscription is displayed ANT.

3) Mode "compass"- to listen to call signs of stations

and for indication CUR on the device KI 227. In this mode

on the left of the panel KR-87 the inscription is displayed ADF.

4) Transfer from mode ANT to mode ADF carried out by pressing

buttons ADF on the panel KR-87.

5) Mode BFO– for direction finding when the radio station is operating in

telegraph mode Turns on by pressing the corresponding button on KR-87.

Methodical Based on the distribution characteristics NE ARC may have:

ARK errors: 1) Radio deviation (∆Р) is the deviation of the loop antenna from the true direction by PRS, which occurs due to the fact that secondary radiation distorts the main radio field PRS near the plane. ∆Р depends mainly on the relative position of the aircraft and PRS, i.e. from KURA, therefore, radio deviation is automatically compensated in the loop antenna unit by a special mechanical (pattern) device.

2) Errors arising due to the influence of: a) night, b) mountain, c) coastal effects during the propagation of radio waves (Fig. 2a, b, c). Can reach values 30º-40º. Taken into account by the pilot when flying in appropriate conditions.

Day Night The night effect occurs during

morning and evening dawn, when appearing -

F the spatial ray disappears or disappears,

E which causes the needle to oscillate ARK.

Earth

PRS 1 The mountain effect occurs when

flying near mountains whenever possible

Proved that electromagnetic energy can be sent into space in the form of radio waves that travel through the atmosphere at approximately the speed of light. This discovery helped develop the principles of radio communication that are still used today. In addition, the scientist proved that radio waves are of an electromagnetic nature, and their main characteristic is the frequency at which the energy oscillates between electric and magnetic fields. Frequency in hertz (Hz) is related to wavelength λ, which is the distance a radio wave travels during one oscillation. Thus, the following formula is obtained: λ = C/F (where C is equal to the speed of light).

The principles of radio communication are based on the transmission of information-carrying radio waves. They can transmit voice or digital data. To do this, the radio station must have:

Device for collecting information in electrical signal(for example, a microphone). This signal is called baseband in the normal audio range.

Modulator for introducing information into the signal frequency band at the selected

A transmitter, a signal that sends it to the antenna.

An antenna made of an electrically conductive rod of a certain length that will emit an electromagnetic radio wave.

Signal amplifier on the receiver side.

A demodulator that will be able to restore the original information from the received radio signal.

Finally, a device for reproducing the transmitted information (for example, a loudspeaker).

The modern principle of radio communication was conceived at the beginning of the last century. At that time, radio was developed primarily to transmit voice and music. But very soon it became possible to use the principles of radio communication to transmit more complex information. For example, such as text. This led to the invention of the Morse telegraph.

Common to voice, music or telegraph is that the basic information is encoded in which is characterized by amplitude and frequency (Hz). Humans can hear sounds ranging from 30 Hz to approximately 12,000 Hz. This range is called the audio spectrum.

The radio frequency spectrum is divided into different spectrums, each of which has specific characteristics regarding emission and attenuation in the atmosphere. There are communication applications described in the table below that operate in one or another range.

Today it is difficult to imagine what humanity would do without radio communications, which has found its application in many modern devices. For example, the principles of radio and television are used in mobile phones, keyboards, GPRS, Wi-Fi, wireless computer networks and so on.

"Radio waves" transmit music, conversations, photos and data invisibly through the air, often over millions of miles - this happens every day in thousands of different ways! Even though radio waves are invisible and completely undetectable by humans, they have completely changed society. Whether we're talking about a cell phone, a baby monitor, a cordless phone, or any of the thousands of other wireless technologies, they all use radio waves to communicate.
Here are just a few everyday technologies that rely heavily on radio waves:

• AM and FM radio broadcasts
• Cordless phones
• Wireless networks
• Radio controlled toys
• Television programs
• Cell phones
• GPS receivers
• Amateur radio
• Satellite communications
• Police radio
• Wireless watches

Just a minute joke

The simplest radio

Radio can be incredibly simple, and by the turn of the century this simplicity made early experimentation possible for just about anyone. How easy is it to get a radio? One example is described below:

• Take a fresh 9-volt battery and a coin
• Find an AM radio and tune it to the drive area where static will be heard
• Now hold the battery close to the antenna and quickly press the two terminals of the battery with a coin (so that you connect them together for a moment)
• You will hear a crackling sound in the radio which is caused by the coin connecting and disconnecting

More complex radio

In the early days, radio transmitters were called spark coils, and in addition they produced a continuous stream of sparks at much higher voltages (e.g. 20,000 volts). High voltage, accordingly, contributed to the creation of large sparks, such as you see in a spark plug, for example. Today a transmitter like this is illegal because it spams the entire radio frequency spectrum, but in the early days it worked great and was very common because there weren't many people using radio waves.

Radio Basics: Parts

Any radio installation has two parts: transmitter(transmitter) and 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 deciphers the message from the sine wave that it receives. Both the transmitter and receiver use antennas to radiate and capture the radio signal.

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 important characteristics typical baby monitor:

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

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)

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

Simple transmitters (transmitters)

You can get an idea of ​​how a radio transmitter works by starting with a battery and a piece of wire. As you know, a battery sends electricity (a flow of electrons) through a wire when it is connected between two terminals. The moving electrons create a magnetic field surrounding the wire, and the field is strong enough to affect the compass.

Let's say you take another wire and place it parallel to the battery wire by a few inches (5 centimeters). When you connect a very sensitive voltmeter to a wire, the following will happen: Each time you connect or disconnect the first wire from the battery, you will feel a very small voltage and current in the second wire; any change in the magnetic field can cause an electric field in the conductor - this is the basic principle behind any electric generator. So:

• The battery creates a flow of electrons in the first wire
• Mobile electrons create a magnetic field around the wire
• The magnetic field extends to the second wire
• Electrons begin to flow in the second wire every time the magnetic field in the first wire changes

One important thing to note is that electrons only flow in the second wire when you connect or disconnect the battery. A magnetic field does not cause electrons to flow in a wire unless the magnetic field changes. Connecting and disconnecting a battery changes the magnetic field (connecting a battery to a wire creates a magnetic field, while disconnecting it destroys it). Thus, the flow of electrons flows in the second wire at those two moments.

Transfer of information

If you have a sine wave and a transmitter that sends the sine wave into space with an antenna, you have a radio station. The only problem is that the sine wave contains no information. You have to modulate the wave in some way to encode information on it. There are three common ways to modulate a sine wave:

Pulse Modulation- in PM you simply turn the sine wave on and off. This is an easy way to send Morse code. PM is not that common, but one good example It is a radio communication system that sends signals to radio-controlled clocks in the United States of America. One PM transmitter can cover the entire United States of America!

Frequency
One feature of a sine wave is its frequency. The frequency of a sine wave is the number of times it oscillates up and down per second. When you listen to an AM radio broadcast, your radio is tuned to a sine wave at a frequency of approximately 1,000,000 cycles per second (cycles per second are also known as Hertz). For example, 680 on the AM dial is 680,000 cycles per second. FM radio signals operate in the range of 100,000,000 hertz. Thus, 101.5 in the FM dial will be listed as 101500000 cycles per second.

AM signal reception

Here's a real world example. When tuning your AM car radio to a station such as 680 on the AM dial, the transmitter's sine wave is transmitting 680,000 hertz (the sine wave repeats 680,000 times per second). The DJ's voice is modulated on this carrier wave by changing the amplitude of the transmitter's sine wave. The amplifier boosts the signal to something like 50,000 watts for a large AM station. The antenna then transmits radio waves into space.

So how does your car's AM radio - the receiver - receive the 680,000 hertz signal that is sent by the transmitter and extract information (the DJ's voice) from it? Next, I will list the steps of this process for you:

• Unless you're sitting right next to the transmitter, your radio needs an antenna to help pick up the transmitter's radio waves from the air. An AM antenna is simply a wire or metal stick that increases the amount of metal with which the transmitter's waves can interact.
• Your radio also needs a tuner. The antenna will receive thousands of sine waves. The tuner's job is to separate one sine wave from the thousands of different radio signals that the antenna receives. In this case, the receiver is configured to receive a signal of 680,000 hertz. Tuners work using a principle called resonance, meaning the tuners resonate and amplify one particular frequency while all other frequencies are ignored in the air. A resonator, by the way, can be easily created using a capacitor and an inductor.
• The tuner causes the radio to receive just one sine wave frequency (in our case, 680,000 hertz). Now the radio must extract the DJ's voice from this sine wave - this is done through one of the parts of the radio called a detector or demodulator. In the case of AM radio, the detector is designed so that it has electronic components, called diodes. A diode allows current to flow in one direction and only through it.
• The radio then amplifies the clipped signal and sends it to the speakers (or headphones). The amplifier is made of one or more transistors (the more transistors, the greater the gain and therefore more power goes to the speakers).

Antenna Basics

You've probably noticed that almost every radio, be it a cell phone, a car radio, or more, has an antenna. Antennas come in all shapes and sizes, depending on the frequency the antenna is trying to receive. Radio transmitters also use extremely tall antenna towers to transmit their signals.

The idea of ​​an antenna in a radio transmitter involves launching a radio wave into space. At the receiver, the idea is to take as much data from the transmitter as possible and supply it to the tuner. For satellites that are millions of miles away, NASA uses huge satellite dishes up to 200 feet (60 meters) in diameter - just imagine an oil painting like this.

The size of the optimal radio antenna is related to the frequency of the signal the antenna is attempting to transmit or receive. The reason for this relationship has to do with the speed of light, which can send electrons over long distances. The speed of light is 186,000 miles per second (300,000 kilometers per second).

Antennas: real examples

Let's assume you are trying to build a radio tower for a 680 AM radio station. It transmits a sine wave with a frequency of 680,000 hertz. In one sine wave cycle, the transmitter will move electrons into the antenna in one direction, switch and hold them, switch again and expose them, and then switch again and bring them back. In other words, the electrons will change direction four times during one sine wave cycle. If the transmitter operates at 680000 hertz, this means that each cycle is completed in (1/680000) 0.00000147 seconds. One quarter of this is 0.0000003675 seconds. At the speed of light, electrons can travel 0.0684 miles (0.11 kilometers) in 0.0000003675 seconds. This means that optimal size antenna for a 680,000 hertz transmitter is 361 feet (110 meters). Therefore, AM radios need very tall towers. For a mobile phone operating on the 900000000 (900 MHz) frequency, on the other hand, the optimal antenna size is around 8.3 centimeters or 3 inches - which is why mobile phones can have such short antennas.

You might wonder why when a radio transmitter transmits something, the radio waves want to propagate through space far from the antenna at the speed of light. Why can radio waves travel millions of miles? It turns out that in space the magnetic field created by the antenna induces an electric field in space. This electric field, in turn, induces another magnetic field in space, which induces another magnetic field, which induces another magnetic field, and so on. These electric and magnetic fields (electromagnetic fields) force each other through space at the speed of light, thus traveling far from the antenna. That's all for today. I hope that the article was very interesting, informative, useful and that you learned a lot about everyday technology.