How the transmitter and receiver work. Interference and am. Simple detector receiver

Six o'clock in the morning Moscow time. The measured strikes of the Kremlin chimes rush into space, and then the solemn sounds of the anthem are heard. As soon as its last notes sounded, the calm, clear voice of the announcer was heard: “Moscow speaking.”

Thus begins the day of central radio broadcasting. Do you know how these transfers occur?

How does every sound that originates in a radio studio, on a theater stage, or in any other place from which a radio broadcast is broadcast, instantly reach you hundreds and thousands of kilometers away? In order for us to hear a radio program, we must first transmit it and then receive it.

Rice. 1. Sound waves around a tuning fork.

Rice. 2. Microphone operation. but there is no sound, direct current flows in the microphone circuit; b under the influence of sound the membrane is concave, the resistance has decreased, the current has increased: c under the influence of sound the membrane has been curved, the resistance has increased, the current has decreased.

The task of the transmitting radio station is to turn speech, singing music into electric current, and then convert the latter into electromagnetic waves and radiate them into the surrounding space.

How is this problem practically solved? To find out, let's remember what sound is. Sound is vibrations of any medium: air, wood, metal, water, etc. Sound vibrations in an unlimited space propagate from the sound source along radii in all directions. The average speed of sound propagation in air is 330 m/sec.

In Fig. Figure 1 conventionally shows (actually invisible to the eye) periodic “condensations” and “rarefactions” in a sound-conducting medium, which represent sound vibrations or a sound wave.

Our ear is capable of perceiving as sound only vibrations of certain frequencies (from 16 to 20,000 vibrations per second). In addition, the amplitude of these vibrations must be large enough, that is, the sound must have a certain strength, otherwise we will not be able to hear it.

Microphone

Both electromagnetic waves and sound are vibrations, but of a different nature. Is there a way to turn sound vibrations into electromagnetic waves? Eat. To do this, you first need to convert sound into vibrations of electric current.

A device that converts sound vibrations into electrical vibrations is called a microphone. Let us describe the principle of operation of the simplest microphone.

In Fig. Figure 2 shows a metal chamber into which coal powder is poured. On one side, this chamber is closed by a flexible plate mounted on insulators; on all other sides the chamber is tightly closed. The camera and plate are connected to a constant voltage source, which creates a direct current in the circuit. But imagine that we started talking as we approached the record. If the plate is thin enough, then under the influence sound waves, i.e., condensations and rarefactions of air, it begins to fluctuate. When the plate vibrates, the force of its pressure on the coal powder will change, which will change the resistance provided by this powder to the electric current. The current value will begin to change. As a result, a pulsating current will flow in the circuit. Using fairly simple electrical devices, it is easy to divide the pulsating current into alternating and direct.

We have managed to turn sound vibrations into alternating electric current. But the fact is that the electrical vibrations created by the microphone are very weak; they should be amplified using radio tubes used in special devices - low-frequency amplifiers, and after that they can be transmitted via wire to a radio station.

To understand how a radio station works, you will have to return to the oscillating circuit.

Again about the oscillatory circuit. Let's remember our reasoning. By emitting radio waves, the antenna continuously sends high-frequency electromagnetic energy into space, portion after portion. The antenna supplies this energy from the oscillating circuit.

Where does he constantly draw energy from? oscillatory circuit? Obviously, it is necessary to implement a device that transfers more and more amounts of energy to the circuit to replace those that it usefully transfers to the antenna, and those that it uselessly spends in itself. It cannot be assumed that the oscillatory circuit operates like some kind of “eternal” pendulum.

Now we must talk about the operation of devices that ensure the creation of radio waves.

Radio engineering knows many different ways to “throw” energy into an oscillatory circuit. All of them, with the exception of one, were rejected by practice. The fact is that new portions of electrical energy must be added to the circuit in time with the oscillations. An ill-timed portion of electrical energy will not only not support the oscillations, but will drown them out.

The most suitable method by which new and new quantities of electrical energy are transferred into the circuit has been used for about 40 years. We mean the use of a vacuum tube, which is the soul of modern radio technology.

To get acquainted with how vacuum tube together with the oscillatory circuit creates high-frequency currents; we will take a three-electrode lamp as the main “actor”. To simplify the explanation of the operating principle of a radio transmitter, we will use this old, honored veteran, rather than modern, more complex generator tubes.

An instructive episode. There is an interesting episode from the history of the development of the steam engine. One boy was assigned to a primitive antique steam engine. The boy's duties were simple, but very monotonous. At strictly defined points in time, he had to open and close the tap. It was important not to get confused and not to open the tap ahead of time, so as not to stop the machine. Boy; Endowed with natural intelligence, he was tired of the tedious task. Wanting to find at least a little free time for his games, he resorted to a trick. He connected the tap with ropes to the swinging rocker arm of the machine, leaving the machine itself to take care of opening and closing the tap at the right moments. The machine was transferred from manual to automatic operation. The taps opened and closed without touching hands.

This episode is reminiscent of what happened two centuries later with the invention of the tube high-frequency current generator. In 1913, the first tube oscillator circuit was developed, which laid the foundation for a number of other circuits that provide convenient ways of producing high-frequency currents.

At this time, they knew that a radio tube could amplify weak alternating electric currents of almost any frequency. They also knew that if the gain of one lamp is not enough, it is possible to turn on several electronic lamps in successive steps, one after the other. Undoubtedly, even before this time it was considered possible to feed powerful high-frequency oscillations amplified in this way directly into the antenna. The idea of ​​​​creating a tube transmitting radio station was knocking on the door. One thing was missing: the ability to solve the problem of where to get the initial alternating current, which should be supplied to the grid of the first amplification tube.

And the scientists came up with an idea that, from the outside, had a lot in common with the childish cunning of the boy who serviced the steam engine. They decided to make the vacuum tube self-service. Let her not wait until she is about to be served at the net alternating voltage, and she takes care of it.

Rice. 3. Scheme of a generator with transformer coupling.

In other words, the lamp was forced to not only amplify previously created alternating currents somewhere, but also to excite and generate them.

Thus, the first tube generator of continuous oscillations was created. The first tube generator. The circuit of this generator is extremely simple (Fig. 3). In the anode circuit of the electron tube (triode) L, an oscillatory circuit LC is included, and in the grid circuit of the lamp there is a coil Lc, located closely in the contour coil L. That's the whole generator.

To understand how a tube oscillator works, let's make a small assumption. It is only needed for a short time, and we will soon abandon it. Let us imagine that undamped oscillations are already maintained in the LC oscillatory circuit. The current in the coil L continuously changes its direction, and the capacitor C is charged and discharged at the same frequency. Following changes in the current in the circuit, the magnitude and direction change magnetic field around the coil L, appearing and disappearing, it acts on the turns of the coil L c (crosses them) and, as happens in any transformer, induces voltage in them by induction.

But the lamp grid is connected to the coil L c; therefore, with the same frequency with which the current in the circuit fluctuates, the voltage on the grid will also change. The grid operates automatically, it does not make mistakes: a “plus” on the grid increases the anode current flowing through the lamp, and a “minus” reduces it.

The swing can be rocked by pushing it to the beat. This duty in the lamp is performed with great diligence by the grid, which receives either positive or negative charges. It does not give rest to the anode current, forcing it to perform continuous oscillations.

So, the anode current cannot flow calmly. As long as the filament (cathode) of the lamp is heated and there is a positive voltage at the anode of the lamp, the lamp generator creates undamped oscillations. The lamp, using the energy of anode battery B, covers all losses in the circuit. This results in a kind of “ideal” oscillatory circuit. The problem of obtaining undamped oscillations has been solved.

A tube generator can be likened to a wound spring clock or a wall clock with raised weights. The elasticity of the spring or the weight of the weights completely compensates for all the braking forces of friction and makes the clock mechanism work non-stop.

Now we can discard our assumption. Let there be no damped oscillations in the anode circuit: But the very first impulse of current caused by turning on the generator will create a magnetic field around the circuit coil. This impulse will be transferred to the grid, and it will immediately do its job. The swing will start moving. Swinging more and more, they will reach maximum swings, at which the swinging efforts are just enough to overcome all the forces trying to stop the oscillations.

It was possible to precisely build a generator that runs itself, without manual or mechanical control. He forces himself to act, he excites himself. Therefore, such a generator is called self-exciting.

Feedback. Separate the loop and grid coils over a large distance so that the magnetic field of the loop coil does not “catch” on the turns of the grid coil, and it’s all over. Oscillations are created only by the flow that the anode circuit is connected to the grid and transmits exciting impulses. This connection is called feedback: instead of the oscillations from the anode circuit going somewhere further, “to the output,” they are (not completely, but partially) transmitted back to the grid of their own lamp. The grid coil by which the grid communicates with the anode circuit is called a feedback coil. The more turns there are in it and the closer it is located to the loop coil, the greater the voltage induced in it, the stronger the connection.

So, it is not the electron tube that creates the oscillations; they are created in the oscillatory circuit. But the circuit would never have created continuous oscillations if the lamp had not thrown more and more amounts of electrical energy into the circuit to compensate for all losses - useful and harmful. But the lamp could not transmit anything to the circuit if it did not receive energy from power sources, batteries or electric generators that supply voltage to the anode.

The rate of oscillation, or better yet, the frequency, is imposed by the oscillatory circuit. The oscillations are slow, and the electron tube will transfer successive portions of electrical energy to the circuit at the same slow pace. But it will not be difficult for her to do this at a speed of several million or tens and hundreds of millions of times per second. Try manually controlling electrical energy at such speed!

Three point

We have already indicated that the lamp grid is completely indifferent to where the “swing” is supplied to it from. In the diagram in Fig. 3 feedback of the anode circuit to the grid transformer. It was soon proven that it was not necessary to have a separate feedback coil. To do this, we used a circuit in which the grid (Fig. 4) is directly connected to the loop coil L. The voltage generated on the AB part of the loop coil turns is applied to the grid of the lamp L. The more turns there are between points A and B, the more voltage is applied to the grid, the stronger the feedback. On the contrary, by moving the connecting conductor of the grid to point B, we would reduce the feedback. This connection is called autotransformer. In principle, it is no different from a transformer. Both methods represent types of inductive coupling: voltage on the grid is created due to electromagnetic induction.

An indispensable condition for the operation of the circuit is such a connection of three conductors from the lamp L to the LC circuit, in which the wire from the cathode (filament) is connected between the wires from the anode and the grid. Only then will the grid and anode pulses act in time. If the anode current, for example, must increase, then for this the positive voltage on the grid must increase.

Radio specialists call the supply of portions of energy from the lamp to the circuit strictly in time as in-phase supply. A transformer-coupled circuit may fail to excite if the grid pulses are out of phase with the anode current pulses. In this circuit, correct phasing is achieved very simply: if the generator is not excited, just switch the ends of the grid coil. In a circuit with autotransformer coupling, it is necessary to arrange the conductors only as shown in Fig. 4.

Very simple in design, consisting only of an oscillating circuit connected to a lamp at three points, this circuit was at one time especially favored by radio amateurs. Almost all radio transmitters of the first shortwaves had a three-point generator.

Master oscillator

A tube self-excited generator still lacks an antenna to become a radio transmitter. The difference between high-power and low-power radio stations lies mainly in the degree of amplification of the high-frequency oscillations initially obtained in the tube generator.

Rice. 4. Generator circuit with autotransformer coupling.

If more power is required than what a self-exciting generator is able to supply directly, then stepwise amplification is used with increasingly more powerful lamps. Sometimes in one powerful amplifier stage, to increase the power, several lamps are simultaneously switched on “in a common harness” - two, three or more. You can often find a transmitter with three or four or even seven or eight stages. Under such conditions, a self-exciting tube oscillator, the primary source of electrical oscillations, is called a master oscillator: it “sets the tone” for all the other amplification stages and “swings” them.

Master oscillator"heart" of the transmitter. The “heart” will stop and everything will stop. The first amplification stage will not receive anything to the lamp grid from the driving stage and therefore will not transmit anything to the second stage, the second will have nothing to transmit to the third, etc. The antenna will wait in vain for receiving high-frequency currents from the powerful final stage.

And the “heart” of the transmitter is carefully protected. Overload is harmful to him. It is affected by the heat generated by the current in various parts of the installation. Any change in temperature leads to a change in the size of metal structures, in particular to a change in the size of the parts of the capacitor and the circuit coil. The inductance changes, the capacitance changes, and this changes the generated frequency, the wave of the radio station “walks”. In search of station signals, you have to constantly rebuild the receiver.

To avoid troubles, the master oscillator is not required to high power as long as it generates oscillations of a strictly defined frequency. Just as a delicate plant is placed in a greenhouse, the master oscillator is often placed in a chamber with a strictly constant temperature. More often, special frequency stabilizers are used, which do not allow the generated frequency to deviate from a predetermined value, from the nominal frequency.

The connecting link between the tube generator and the antenna is the supply line (feeder). It plays the role of a plus in a simple arithmetic expression:

radio transmitter = tube oscillator + antenna.

The supply line consists of wires or cables connecting the antenna to the tube generator. Thus, we became acquainted with the general principle of operation of the radio transmitter.

We turn on the radio transmitter. Any type of work can be carried out through radio transmitters: transmission of radiograms using the telegraph alphabet (radio telegraph transmission), transmission of speech and music (radio telephone transmission), letter printing and transmission of images.

The simplest type of work is interruption of oscillations; This is what radio operators do when they tap out the telegraph signs with a key: when the key is pressed, its contacts close and a series of high-frequency oscillations enter the antenna; when the contacts are opened, the supply of oscillations to the antenna is interrupted. A short switching time corresponds to a dot, a long switching time corresponds to a dash. This process is called manipulation (Fig. 5).

But in this way only conventional signs of the telegraph alphabet can be transmitted. And if you need to transmit speech or music, then first of all you should turn to the help of a microphone.

We already know about the first stage of converting sound into electric current. We amplified this current and sent it through wires to the radio station. Thus, sounds came to the transmitter in the form of low-frequency electrical oscillations. What to do with them now?

Modulation. Radio waves used for long-distance broadcasting have a length from 15 to 2000 m, which means that the frequency with which the electric current that causes them oscillates is 20,000,000 (20 MHz) 150,000 (150 kHz) vibrations per second. The highest sound (low) frequency that our ear can perceive has approximately 20,000 vibrations per second.

Thus, it turns out that the vibrations that we can hear have a very low frequency and are therefore unable to be radiated into space.

Rice. 5, High frequency current in the transmitter antenna during telegraph operation.

Rice. 6. Graphic representation of the modulation result.

Oscillations emitted over vast distances in the form of electromagnetic waves have a very high frequency. We cannot hear such vibrations.

It remains, apparently, to somehow adapt high-frequency vibrations to “transport” vibrations, the sound frequency. This method was found. Sound frequency vibrations cause high frequency vibrations to be affected. The process of influencing low-frequency vibrations on high-frequency ones is called modulation.

Electrical vibrations of sound frequency are difficult to transmit far, but with the help of high frequency they are freely transferred around the entire globe.

The term “modulation” has long been used in music to denote the transition from one key to another change of modes.

In electrical engineering, modulation is a change in any of the characteristics of an electric current - its magnitude, frequency, phase - in accordance with the fluctuations of some other current.

Modulation this is not just a mixing of currents, but such an effect of a low-frequency current on a high-frequency one, when the low-frequency current seems to imprint its shape on the high-frequency one.

High frequency current affected by telephone conversation, is called modulated current, modulated oscillation. They also say: carrier vibration. It's an apt name. It shows the essence of the process well. A high-frequency oscillation after modulation bears on itself (or in itself) the imprint of a low-frequency current.

The modulation process is carried out using a special device called a modulator. The modulator influences low-frequency currents on high-frequency oscillations. This is done in radio transmitters using special modulating lamps.

High-frequency oscillations before modulation are no different from one another. But due to the action of electrical vibrations coming from the microphone, their amplitude changes. It gets bigger and smaller. These changes exactly correspond to fluctuations in the microphone current, and therefore to sound vibrations. Thus, high-frequency electrical oscillations are imprinted with a “print” (pattern) of transmitted sounds, and the result is modulated oscillations that are emitted by the radio station (Fig. 6).

The purpose of radio transmitting stations is very diverse. Some of them broadcast for the entire country and are located in large premises. An amateur radio station is often freely placed on a table in a shortwave operator's apartment. But no matter how different they are in appearance and size, there is no fundamental difference in their work. Radio engineering processes they are almost identical and they differ mainly only in the oscillation power and the length of the emitted radio waves.

Every radio station is a factory of radio waves. It consumes electrical energy from batteries or a generator, or from the electrical network and converts it into high-frequency electrical oscillations, which, after amplification and modulation, enter the transmitting antenna. From here they begin their journey to radio receivers in the form of radio waves.

4. Operating principle of the transmitter

The signal from sensors or any other sources of analog information is sent to high-speed analog switches. The operation is controlled by a time division circuit consisting of decoder 1, counter 1 and pulse generator 1. The circuit operates as follows:

Pulse generator 1 produces short distance pulses, the distances between which are equal to the ADC conversion time. These pulses are counted by a three-bit asynchronous pulse counter whose graph looks like this:

Such a counter can be easily implemented on three synchronous D-flip-flops. The three-bit binary code from counter 1 goes to decoder 1, which, depending on the code, connects the corresponding channels.

Thus, to the input of A.C.P. arrive sequentially analog signals from the corresponding analog inputs. A.C.P. synchronized by a bit generator. This is a generator of short pulses, the distance between which is equal to the duration of an elementary symbol in the code. The ADC, as a rule, contains a parallel register at the output, the outputs of which are in the so-called third state (high impedance). To ensure data output, an enable signal is needed; it comes from pulse generator 1. After outputting the parallel code, the outputs of this register automatically switch back to the third state.

With A.C.P. A 9-bit parallel code of the command word is output, which is fed to the code converter from parallel to serial. Such a converter can be implemented on a parallel-serial register, which is also synchronized from a bit generator.

A 63-bit M-sequence is used as a sync word. The sync word must be at the beginning of the frame. The synchronization word formation scheme can be made on the basis of an M-sequence generator and on the basis of a P.Z.U. The first version of the scheme (Fig. 1) works like this:

There is an M-sequence generator (MSF), which is easily implemented using linear switching circuits based on shift registers. We will not consider the principle of formation in this project; it is discussed in great detail in the literature. As a clock signal for F.M.P. A bit pulse generator is used. Sequence generation begins when a high level signal arrives from the comparison circuit (start signal). Such a signal is only possible if the first channel is connected and output from the A.D.P. has begun. the first code word. To form a 63-bit M-sequence, 64 pulses are required. The circuit for counting these pulses is made on counter 2 and decoder 2. As soon as the counter counts 64 pulses, a high-level signal (stop signal) appears at the corresponding output of the decoder, which stops the F.M.P. Since counter 2 will constantly count pulses from the bit pulse generator, at the moment the formation of the M-sequence begins, it must be returned to its original state (reset). To do this, the start signal from the comparison circuit is fed to a switch, which connects a high-level signal for a short time to the counter reset input. Stop signal. also transfers the code converter register from the third state to the working state and from its output the M-sequence begins to appear in serial binary code. As soon as all 63 bits of the sync word leave the register, it automatically enters the third state.

The second version of the scheme (Fig. 2) for the formation of the M-sequence is based on the use of P.Z.U. The operating principle is as follows:

Similar to the circuit with the M-sequence generator, there is a start signal. He enters the P.Z.U. and puts it into read mode. In P.Z.U. the required 63-bit M-sequence is pre-programmed. Also on P.Z.U. a synchronization signal is received from the bit generator, as in the previous circuit. The synchronization word comes out in parallel code from the P.Z.U. and enters the code converter in the form of a register. After the withdrawal of the P.Z.U. exits the reading mode and waits for the start signal. The start signal also puts the code converter into operation, and the output of the sync word in serial code begins under the influence of the synchronization signal coming from the bit generator. This circuit is the simplest since it requires fewer control signals compared to the circuit on the driver. It is also smaller in size, cheaper and more reliable since fewer radioelements and P.Z.U. chips are used. such small capacities are very cheap. In my work, I considered the simplest version of the circuit. In general, as a rule, such formation circuits are made on a microprocessor kit or microcontrollers, then all control can be carried out by software through I/O ports.

The sync word goes to the adder, where it is summed with code words. To avoid overlapping the sync word with the code words, it is necessary to delay the code words for a time equal to the duration of the sync word. This is done using digital line delay or memory block.

As a result, a frame is formed consisting of a sync word and 7 code words, separated by time. Next, the signal goes to the high-frequency frequency. cascade (Fig. 3) where it enters the phase manipulator, with the help of which the subcarrier is manipulated. The generated phase-shift keyed signal on the subcarrier carries out phase modulation of the carrier oscillation.

On the w.ch. cascade

On the w.ch. cascade

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Operating principles of radio transmissionmeter and radio receiver

radio transmitter radio receiver tension

Radio broadcasttchik (radio transmitting device)- devices for generating radio signals intended to transmit information over a distance using radio waves. They generate radio signals with specified characteristics necessary for the operation of specific radio equipment. systems and radiate them into space.

Functionally, the radio transmitter consists of the following parts:

Any radio communication system includes radio transmitting devices, the functions of which include converting direct current energy from power sources into electromagnetic oscillations and controlling these oscillations.

Energy transfer via radio communication is widely used in the control of automatic objects.

The main radio communication devices are a radio transmitter and a radio receiver. The radio transmitter is designed to create a high-frequency signal, some parameters of which (frequency, amplitude or phase) change according to the law corresponding to the transmitted information. The frequency of the high frequency signal is called the carrier. The first radio transmitters of the spark principle of operation based on the Ruhmkorff coil were very simple in design - a spark discharge served as a radio wave emitter, and a telegraph key served as a modulator. With the help of such a radio transmitter, information was transmitted in encoded discrete form - for example, Morse code or another conventional set of signals. The disadvantages of such a radio transmitter were relatively high power, required for the effective emission of radio waves by a spark discharge, as well as the very wide radio frequency range of waves emitted by it. As a result, the simultaneous operation of several closely located spark transmitters was practically impossible due to the interference of their signals.

A modern radio transmitter consists of the following structural parts:

· master frequency oscillator (fixed or tunable) of the carrier wave;

· a modulating device that changes the parameters of the emitted wave (amplitude, frequency, phase or several parameters simultaneously) in accordance with the signal that needs to be transmitted (often the master oscillator and the modulator are performed in one block - the exciter);

· power amplifier, which increases the exciter signal power to the required level due to external source energy;

· a matching device that provides maximum efficient transfer amplifier power to the antenna;

· antenna providing signal radiation.

Radio- a device connected to an antenna and used for radio reception.

A radio receiver (radio receiving device) is a device for receiving electromagnetic waves of the radio range (that is, with a wavelength from several thousand meters to fractions of a millimeter) with subsequent conversion of the information contained in them to a form in which it could be used.

Classification of radio receivers

Radio receiving devices are divided according to the following characteristics:

· for the main purpose: radio broadcasting, television, communications, direction finding, radar, for radio control systems, measuring, etc.;

· by type of work: radiotelegraph, radiotelephone, phototelegraph, etc.;

· by type of modulation used in the communication channel: amplitude, frequency, phase;

· according to the range of received waves, according to the recommendations of the CCIR:

· myriameter waves - 100-10 km, (3 kHz-30 kHz), VHF

· kilometer waves -- 10-1 km, (30 kHz-300 kHz), LW

· hectometric waves -- 1000--100 m, (300 kHz-3 MHz), NE

· decameter waves - 100-10 m, (3 MHz-30 MHz), HF

· meter waves -- 10-1 m, (30 MHz-300 MHz), VHF

· decimeter waves - 100-10 cm, (300 MHz-3 GHz), UHF

· centimeter waves -- 10-1 cm, (3 GHz-30 GHz), SMV

· millimeter waves -- 10-1 mm, (30 GHz-300 GHz), MMV

A receiver that includes all broadcast bands (LW, MW, HF, VHF) is called all-wave.

· according to the principle of constructing the receiving path: detector, direct amplification, direct conversion, regenerative, super-regenerator, superheterodyne with single, double or multiple frequency conversion;

· by signal processing method: analog and digital;

· according to the applied element base: on a crystal detector, tube, transistor, on microcircuits;

· according to design: stand-alone and built-in (as part of other devices);

· at the place of installation: stationary, portable;

· according to the power supply method: networked, autonomous or universal.

The element that influences high-frequency oscillations is called a modulator. The modulator is an integral part of the radio transmitter, as it generates an information signal to be transmitted over a distance. Modulated high-frequency vibrations are amplified by a power amplifier and radiated into the surrounding space using an antenna.

The decrease in field strength, and therefore the energy flow transferred by a radio wave along the Earth's surface (ground wave), is due to the conductivity of the surface in this region. A flow of energy appears along the conducting surface, directed into the conducting medium and quickly decaying as it propagates through it. The depth of penetration of a radio wave into the earth's crust is determined by the thickness of the layer and, therefore, increases with increasing wavelength. Therefore, long and ultra-long radio waves are used for underground and underwater radio communications. because The greater the number of collisions, the larger part of the energy received by the electron from the waves turns into heat. Therefore, absorption is greater in the lower part. areas of the ionosphere where v is greater, because higher gas density. As frequency increases, absorption decreases. Short waves experience weak absorption and propagate over long distances. Therefore, short waves are used for transmission

Short waves (3-30 MHz) also as a result of their reflection from the ionosphere, communication is possible both at short and long distances with a significantly lower transmitter power level and much simpler antennas than in lower frequency bands.

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High frequency currents flow from the antenna to the receiver. They pass freely through the antenna capacitor C1. Since its capacitance is small, it represents low resistance for such currents. This capacitor serves to eliminate the influence of the antenna on the oscillating circuit and its tuning and is not mandatory. Turning on the antenna capacitor reduces the reception volume, but the receiver acquires an important quality - better selectivity (cancellation from interfering stations) and a large range overlap. Next, the high-frequency currents enter an oscillatory circuit consisting of a coil with a tap (L1 L2) and a variable capacitor C2.

At the moment of resonance, the circuit resistance for the received high-frequency currents becomes very large and a rather large voltage develops on it, which is then supplied to both the control grid and the cathode of the lamp. It enters through the grid capacitor C3, which has a small value, and is amplified by the lamp. From the anode circuit of the lamp, high-frequency currents enter the feedback coil and through capacitor C5 to the cathode of the lamp. The feedback coil L3s is placed inside or next to the loop coil. High-frequency currents passing through coil L3 form an alternating magnetic field around it, the power lines of which will cross the turns of coils L1 and L2 and create additional voltage in them.

As is known, in this case the receiver will receive the station louder, and the sensitivity of the receiver (the ability to receive hard-of-hearing stations) will also increase.

The other part of the high frequency currents will pass through capacitor C5, which has a small capacitance. This circumstance is of significant importance when adjusting the feedback receiver. By changing the capacitance of capacitor C5, you can achieve normal feedback operation.

Some of the high-frequency currents flowing through the lamp will also reach the screen grid. They find their way through the capacitor C4t where they encounter less resistance. High frequencies can also penetrate into power circuits, so a choke or large resistance is often included in the anode of the first lamp.

What happens to low frequency currents? Capacitor C3 and resistance R2 ensure the lamp operates in grid detector mode. Detection occurs in the grid circuit, and the isolated low-frequency currents will be simultaneously amplified by the lamp.

The detected currents in the grid circuit flow through the lamp grid leak and create an alternating low (audio) frequency voltage drop across it. This voltage, like high-frequency currents, is supplied to the control grid of the lamp and creates amplified currents of the same frequency in its anode circuit.

Some of these currents enter the screen grid and return to the cathode through the large capacitor C4. But the bulk of them will pass through resistance R3. (anode load) and will create a voltage drop across it. Next, low frequency currents flow to the power supplies and return to the cathode. Capacitor C5 represents a large resistance for these currents, and they do not pass through it.

The low-frequency voltage generated at resistance R3 through transition capacitor C6 is supplied to the grid of the second lamp, which operates as a low-frequency amplifier.

The presence of vibrations on the grid will cause increased audio frequency currents in the anode of the lamp, which will pass through the loudspeaker and drive it. Low frequency currents will then pass through the current source and return to the cathode.

In order for the second lamp to operate without distortion, a constant negative bias (relative to the cathode) is applied to its grid, which is formed when the anode current of the lamp passes through resistance R6. In the receiver, it is blocked by a high-capacity electrolytic capacitor (with low operating voltage), which removes low-frequency currents from the cathode resistance circuit.

The receiver will work without this capacitor, but its operating volume will be significantly lower.

Another blocking capacitor C7 located in the anode circuit of the lamp drains currents audio frequencies, having the highest frequency, from the winding of a transformer or loudspeaker. Changing the capacitance of this capacitor entails changes in the timbre of the loudspeaker, drowning out high tones to a greater or lesser extent.

The anode load of the second lamp is a high-impedance loudspeaker or an output transformer for a dynamic loudspeaker. It is very important to select the correct transformer for the output tube and the resistance of the speaker voice coil. This explains that all homemade output transformers are subject to careful calculation.

Now let's look at the DC paths in the receiver.

This current is generated in the 0-V-1 receiver as a result of rectification of the alternating current by the 6Ts5 lamp.

How does a rectifier work?

Alternating current from the network is supplied to the autotransformer. It is a type of transformer in which one winding with taps is used as both windings.

If voltage from the network is applied to part of the winding, as is done in the diagram, then an increase in voltage is formed at the opposite ends of the autotransformer. This increased alternating voltage to 220 V is supplied to the anode of the lamp. It is known that the lamp will pass current through itself only at those moments time when its anode will have a positive charge.

The current through the lamp will have a constant direction, but its strength changes periodically and at some points in time is completely absent. This current is called pulsating and is not suitable for powering receivers. Therefore, a filter is installed in the rectifier, consisting of a choke (or resistance) and two electrolytic capacitors (paper capacitors can also be used) of large capacity.

At times when current flows in the lamp, it not only enters the receiver, but also charges the capacitors. At the next moment in time, when a minus appears on the anode, the lamp does not conduct current, but the receiver still receives it due to the discharge of capacitors. The choke in the filter, having a large inductance, further smoothes out the ripples after rectification.

Thus, the AC current is rectified for only one half of each AC period in the network. Such rectifiers are called half-wave rectifiers.

The direct current in the receiver branches into several circuits. First of all, it gets to the anode of the last lamp, passing through the secondary (high-resistance) winding of the output transformer, then it gets to the screen grid of this lamp. After passing through the lamp, these currents will hit the cathode, pass through the bias resistor and return to the rectifier. This will cause some voltage drop across the output transformer and bias resistance.

The next direct current circuit is similar to the circuit discussed and relates to the first lamp.

The direct current will pass through the damping resistance R4 to the screen grid of the first lamp and through the resistance of the anode load R3 to the lamp anode; then these currents will pass through the lamp to the cathode and again return to the rectifier.

All other paths to direct current are closed, since any capacitor represents an infinitely large resistance to it. A young radio amateur, having well understood the purpose and role of all the parts of his receiver, can consciously approach its setup and testing.

Homemade parts for the receiver and installation.

For the 0-V-1 receiver, you need to make loop coils, a feedback coil and a chassis, and for the network receiver, you also need to make an output transformer and a rectifier.

The coils are wound as follows. Two frames in the shape of a cylinder are glued together from thick cardboard or thick paper. One of them is used to place the windings of the loop coils L1 and L2 on it, and on the second, smaller one, the feedback coil L3 is wound. The first frame is fixed motionless, and the second is installed inside the first so that it can rotate.

Rice. 33. Arrangement of coils for receiver 0-V-1 and range switch:

a - sectional view of a contour coil, b - design of a feedback coil, c - slide range switch, d - range switch with a single-pole plug.

The dimensions and arrangement of the coils are shown in Figure 33. Using a long metal (possibly wooden) axis, the frame with the feedback coil is attached inside the frame with coils L1 and L2. To do this, two holes are made in the large frame, one opposite the other. The same two holes, but of a slightly smaller diameter, are made in the small frame. The axle is installed after the coils are wound. The inner frame must be firmly fixed to the axis so that it rotates with it.

Contour coils L1 and L2 are wound in one row with 0.25-0.3 PE wire. First, coil L1 has 80 turns, then coil L2 has 160 turns. It is wound at a distance of 10 mm from coil L1 (this is necessary to install the axis). The ends of the coils are soldered to the output petals mounted on the edge of the frame.

The feedback coil consists of 60 turns, wound in two sections (Fig. 33.6). For this coil, use a thinner wire, 0.1-0.15 mm in diameter, in any insulation.

The beginning of the wire is fixed to the frame in two punctures at a distance of 3 mm from the edge. Then 30 turns of wire are wound in bulk. Without breaking the wire, the second 30 turns are wound through a gap of 6 mm required for the axis. To prevent the wire from jumping off the frame, it is wrapped together with the frame with threads or glued.

The ends from the feedback coil are made up to 15 cm long. It is desirable that in the places where the ends of the L3 coil are secured, a thicker and more flexible wire is soldered to the thin wire. Then, when the coil rotates (360°), these ends will not break.

After the coil is ready, they begin to manufacture the plywood chassis. The dimensions of the chassis are shown in Figure 34. Its design is familiar to us from the battery amplifier, only for the receiver the chassis is made somewhat longer and wider.

If a rectifier is supposed to be installed on the same chassis, then the dimensions of the chassis need to be increased further.

Sockets and clamps are installed on the side and rear walls, as was done in the amplifier for the detector receiver.

On the left wall two sockets are needed for the antenna and grounding. On the right wall the sockets are needed to connect a loudspeaker, and on the back wall - for power supply.

Four more pairs of sockets - for detector D, telephone handsets T1 and T2, filament voltage regulator R7 - are installed near the lamps on the upper strips.

Then the parts are strengthened. A loop coil and a variable capacitor are attached to the wide top bar. The capacitor can be taken of any type with an air or solid dielectric, but its capacity should not differ sharply from the required one.

Rice. 34. General view receiver 0-V-1 battery powered.

If a variable capacitor is difficult to obtain, you can assemble a different type of oscillating circuit. How to do this is described below.

Switch P is easy to make yourself. Figures 33.0 and 33.g show the two simplest homemade switches.

Between the slats (canopy), screws or screws, two eight-pin sockets for lamps are secured.

Then installation is carried out. Figure 35 shows the receiver wiring diagram. How to install tube radio structures is known from previous descriptions.

You need to install the receiver strictly following the diagram, checking the installation as it is done.

Often, when installing radio structures, radio amateurs use free sockets of lamp panels to solder two or three parts. For example, a 2K2M lamp has five legs on the base. Therefore, three sockets remain free on the lamp socket. These free sockets are convenient to use for small parts that must be connected to each other. To avoid hanging soldering, the parts are soldered to the free socket of the socket, using it as a nodal stand during installation.

Fig- 35. Wiring diagram of the battery receiver 0-V-1

Testing and adjustment. First, the receiver can be tested for reception with a crystal detector or zvitector. To do this, an antenna and grounding are connected to the receiver (the grounding in the network receiver is connected through a capacitor with a capacity of 0.1 μF), and telephone handsets are connected to the T1 sockets.

Then the detector is inserted and, by slowly turning the variable capacitor knob, the receiver is tuned to some radio station. After the radio amateur is convinced of the operation of the oscillatory circuit and hears some radio station, lamps are inserted into the receiver.

When testing a receiver with lamps, current is supplied to it from batteries (or from a rectifier). In this case, all precautions must be taken so as not to confuse the incandescent and high voltage terminals.

A loudspeaker is connected to the output jacks. First of all, the action of the feedback is determined. To do this, when tuning the receiver to a station, the feedback coil is slowly turned to different sides and listen for the appearance of rustling or whistling (generation) in the loudspeaker. If generation does not occur, you should swap the ends of the feedback coil. It is possible that in this case you will not hear either noise or whistle; this means that there are few turns on the feedback coil and it should be wound.

When feedback is established, when tuning the receiver to a station (at some positions of the variable capacitor), a whistle occurs. By slowly turning the tuning knob, the whistle is reduced to the lowest pitch. The moment when the whistle disappears will correspond to precise tuning to the station. After this, the feedback knob is turned until the reception is clear of rustles and whistles.

The onset and interruption of generation should not occur immediately (in a jump), but smoothly. This is achieved by selecting the size of capacitors C5 and C8.

Before adjusting the feedback in the receiver, it is advisable to measure the lamp mode using some kind of measuring device.

The finished receiver must be placed in a convenient box, the dimensions and shape of which can be determined by the young radio designer himself.

Receiver care.

Handling the receiver is easy. It is adjusted with the help of variable capacitor C2, and the volume is regulated by rotating the feedback coil. Handles are mounted on the axes of these parts. Figure 36 shows how you can make your own handles with divisions. The highest volume and sensitivity of the receiver occurs at the moment when feedback is on the threshold of generation.

Receiver 0-V-1 is a regenerator. If the feedback in it is large and the oscillating circuit of the receiver, therefore, receives a lot of energy from the feedback coil, then generation occurs. The oscillatory circuit then creates its own oscillations (radio waves), which are emitted as if from a real radio station. This may cause great interference to nearby receiving devices. To avoid this, when tuning the receiver to a radio station, generation must not be allowed to occur.

Rice. 36. Homemade knob for tuning the receiver.

After the end of reception, it is necessary to disconnect the batteries from the receiver (or turn off the rectifier. To do this, it is best to make a special switch in the filament circuit (for the battery version). With a network receiver, such a switch can be installed in the wires supplying electric current to the rectifier

For the receiver it is advisable to use outdoor antenna Up to 15 m long.

First Playing of gramophone records. The 0-V-1 receiver can be used to play back records and for amplification from a microphone. Connect the pickup or piezoelectric tubes with one end to the Control Grid Cap of the first lamp, and the other to the common wire. If the pickup is now placed on a rotating record, the recording being played will sound clear and loud through the loudspeaker. The network receiver has special Sound sockets to turn on the pickup.

With the help of a pickup, radio amateurs often adjust radio structures to achieve good performance of the low-frequency amplifier. In this case, sometimes it is necessary to change the value of resistance R 4 and the size of capacitors C4 and C7.

Second. Tone control. Sometimes it is necessary to change the timbre of a radio broadcast. To do this, a so-called tone control is installed in receivers (or amplifiers).

On the schematic diagrams of the receivers, the dotted line shows a circuit consisting of a capacitor C10 with a capacity of 50 thousand picofarads and a variable resistance R8 of 50-100 thousand ohms.

This circuit is connected between the anode of the second lamp and the common wire. By moving the variable resistance slider down or up, you can change the timbre of the sound.

Third. Volume control. In the 0-V-1 network receiver, when listening to gramophone records, it is advisable to adjust not only the sound timbre, but also its volume

Instead of a constant resistance R5 of the same value or less, replace it with a variable resistance - a potentiometer. Of the three terminals on the potentiometer, connect two (for example, the middle and leftmost ones) first to each other and then to the common wire in the receiver. Connect the third terminal to the control grid of the second lamp.

Now, when you rotate the potentiometer knob, the volume of the sound in the speaker will change.

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. The electromagnetic energy of 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. An 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 has great value 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 to 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 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.

Grounding one half of the antenna makes sense if the soil is a good conductor. 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 refers to the 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 flight and other important information on a working display in the event of failure of one of the PFD or MFD indicators.

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 are located on the pilots’ control handles (Push-To-Talk - an analogue of the “Radio” button).

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, 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 airlines;

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.

Both radio stations, in addition to the transceiver equipment integrated into the GIA 63 units, 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. Similarly, accelerated tuning of radio stations in emergency situations is possible from the database of nearby airfields (NEAREST AIRPORTS).

Manual setting radio stations are controlled by double COM knobs, with the small inner knob setting the frequency values ​​in kHz, and the large outer knob 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 the operating frequency and the prepared frequency, indicated by a blue color and a 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.

The performance of radio stations is monitored 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 units fail digital processing sound signals, 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 of 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, additional buttons “BRG-1”, “BRG-2” will open;

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