Tuning the radio using instruments. Instructions on how to set up a radio on a radio from various manufacturers. Receiver fine tuning

Once upon a time there was a Sony radio, when it was sold they said it was Japanese, the price made me believe it, and later I assured everyone that it came from there. Its objective advantage is pure sound. True, there was a small nuance - the FM scale of the 88-108 MHz range, but at the store there was a magician who, for a “small share”, performed a miracle - he filled the scale with many Russian-speaking radio stations. We used the radio to its fullest extent, but remembering how much was paid for it, we didn’t throw it or at it. So it was not badly preserved, despite its very respectable age. But the radio broadcasting stations that she caught first diminished, and then there were none left at all.

There is a lot of information on the Internet about setting up sound-reproducing equipment, written competently and in detail. This is a blessing for students of radio engineering universities; they can easily be used instead of notes to prepare for exams, but this information will not help the owner of a sick radio; he is not in the business of increasing his intelligence, but of repairing the receiver. Or throw it away, it’s no longer a shame.

He opened the case and began to disassemble it into its component parts. There are no complaints about either the power supply, which turned out to be super primitive, which is at the bottom left, or the tape drive mechanism of the tape recorder, to the right of it. One produces its 12 V “on the mountain”, and the second regularly pulls the magnetic tape.

But I wanted to understand the printed circuit board a little. To warm up, I checked all electrolytic capacitors for the actual presence of capacity and ESR. It's hard to believe, but everyone turned out to be completely fine. I unsoldered and disassembled the volume control - a variable resistor, for example, for revision. Once upon a time, a long time ago, he acted a little badly and was, through a medical syringe with a needle, awarded a portion of machine oil. Does it need a supplement? And there was so much oil in it that I could just put it on the frying pan, blot off the excess, and return it to its place. I washed the board on the side of the printed conductors with formic alcohol specially purchased at the pharmacy (they didn’t give anything else), and then, so that there was no white residue left from it, with hot water and shampoo. It turned out not bad, although this method is perceived by ear as a bit wild.

The wire contacts going to the speaker have been soldered. And around the circumference of the speaker I installed a rim - a flexible tube cut lengthwise from a medical dropper. This is so that the metal of the speaker does not rest on the plastic of the housing - it will definitely not worsen the sound characteristics.

And then, very opportunely, I remembered that the master who was modifying the radio tape recorder spoke about some kind of wire spirals. There were several of them on the board, all in the area of ​​the variable capacitor. Partially assembled the device, turned it on, and at the desired range began to touch the copper wires wound in rings with a screwdriver. Two did not respond, and as soon as I touched the third, characteristic sound changes appeared in the dynamics. Found! Bottom one in the photo. I touched it well with tweezers, but it was dangling. I desoldered it, straightened it and wound it again, on a mandrel of a suitable diameter. Soldered it in place. The FM band came to life. At this point I finally got bolder and let’s move the coils with a screwdriver (increase and decrease the gap between them). In response to my actions, the location and number of stations on the scale began to change. But the most convenient for setting were two tweezers. He stretched and squeezed them like an accordion, only gently. See this action clearly in the video.

Video

As a result, I chose a combination of stations that was suitable for myself and optimally located on the scale. The only difficulty is to do everything slowly, otherwise, you know, you want everything faster. Good luck! The simplest option for a possible restoration repair - settings - was shared by Babay iz Barnaula.

WinAmp. It is very convenient for listening to music files in mp3 format. But it also has one interesting feature - listening to radio stations. Of course, such functions will not surprise anyone; sometimes it is enough to go to the website of a popular radio station and listen to the Internet broadcast. But WinAmp offers users almost 9000 radio stations. And it doesn’t just offer, but sorts by style, direction, language and country.

How to set up a radio in WinAmp

To configure the radio correctly, you need to additionally install the WinAmp Library component for the WinAmp player. It is available for downloading from the Internet from the manufacturer's website. After downloading and installing the additional component, launch WinAmp. Let's start setting up the radio. Go to “Settings” and in the Online Media tab set the number of radio stations to listen to. By default, there are only 600 stations installed, but on the Internet their number is in the thousands. We set the value with a margin of 20 thousand. We exit the player and start searching for radio stations.

Select Internet Radio from the menu. Then in the window on the right we activate the Refresh button. The list of available radio stations will begin to download. From now on you can listen to radio stations.

To configure the radio correctly, you need to filter the list by style and direction. To do this, you can specify several types in the Genre menu - classical, rock, pop, jazz, etc., and you can also select countries. If the list of priorities includes not only news, but also news, then you can filter by topic - politics, sports, regional news. In addition, there is a function to search for radio stations by name. Having selected the radio station you are interested in, activate playback either using the Play button or double-clicking the mouse. You can add your favorite radio stations to your “Favorites” list.

Using the WinAmp player, you can find many unexpected radio stations on the Internet. Foreign radio amateurs often broadcast “intercepted” police or air traffic control radio communications on the Internet. In a word, surveying radio broadcasts is as entertaining as simply “surfing” on the Internet. It will take several months of time and a solid gigabyte to study radio stations.

Please note that WinAmp in radio mode consumes approximately 62 megabytes of Internet traffic per hour of listening. Radio stations transmit at 128 kbit/s, so owners of limited packages should take this fact into account.

Radio receiver - setup, operation

In contrast to a device with a stationary antenna, there are peculiarities in the reception of a radio signal by a car radio, which are determined by the proximity of the antenna to the ground, the constant change in the distance to the transmitter, the repeated reception of reflected signals and the overlap of signals from various radio stations. Due to these features, interference and noise may occur, sound distortion and even complete cessation of radio signal reception.

In addition, the quality of radio signal reception depends on the power of the transmitting station and the distance from the signal source, on the presence of shielding buildings and structures (houses, bridges, etc.), as well as on the influence of terrain conditions (mountains, lowlands, etc.). ).

Comment:When using a cell phone in or near a vehicle, radio interference may occur.

Radio activation

When activated, the infotainment system is activated in radio playback mode if it was set before the system was turned off. To activate the radio from CD playback mode, press the “FM/AM” button (7). Subsequent presses of the button switch the frequency ranges of the receiver in the following order: FM (VHF) « AM (medium and short waves)

When you activate the radio or switch between frequency bands, the frequency of the radio station that was tuned in when you last used the radio is selected.

Setting up the radio

Setting up the radio receiver can be done in the following ways:

Automatic search for radio stations;

Manual search for radio stations;

Search for radio stations by program type (radio data system RDS).

Automatic setup

Automatic frequency tuning is done by pressing the 4-position switch (14) with a short delay - this activates the automatic search for the nearest frequency with the received signal and the display “Seek” appears in front of the operating frequency of the received station. Depending on pressing the right or left sector of the switch, the search is performed in the direction of increasing or decreasing frequencies.

Comment:When auto searching, RDS and TP functions must be disabled (see below).

While searching is in progress, playback sound is muted. After automatic tuning is completed, the radio will begin playing the signal of the newly tuned radio station. If the radio does not find any radio stations, it automatically switches to a search mode with a higher sensitivity. If the search is unsuccessful and after this attempt, the signal of the radio station selected before starting the search will be played.

Manual setting

If necessary, the frequency of the desired radio station can be tuned manually.

Attention:Frequency setting should not be done while the vehicle is moving!

When you briefly press the 4-position switch button (14), the frequency change will occur step by step when you press the right sector towards increase, when you press the left sector - towards decrease. This function is used to fine-tune the frequency. If you know the frequency of the required radio station, keep the corresponding sector of the switch (14) pressed until this frequency is reached - the inscription “MAN” appears on the display in front of the current frequency of the radio station. While searching, the playback sound is muted and reactivated when the button is released.

Radio Data System RDS (FM)

Radio Data System (RDS) is a broadcast service that allows FM stations to transmit additional digital information along with the normal radio program signal. Radio receivers equipped with Radio Data System and Internet Interface (RDS/EON) decoders, when tuned to the broadcast frequencies of a number of FM radio stations, are capable of reading special service information, which allows the use of some additional functions, such as determining the name of the radio station, automatically switching to alternative broadcast frequencies of the selected radio station, determination and transmission of traffic information service messages, search for programs on a given topic, etc.

To activate the RDS function, you must briefly press button (1) - the corresponding indicator should light up in the display field. If the currently tuned radio station does not support the RDS format, the radio automatically searches for the nearest signal of the corresponding radio station. In the display field, instead of the current frequency, the name of the radio station broadcasting will be displayed.

Comment:When you turn on the automatic radio station storage function (see below), the RDS function is automatically activated.

To deactivate the RDS function, you must press the button (1) again; the corresponding indicator on the display should go out, and instead of the name of the radio station, the current tuning frequency will be displayed.

Selecting RDS radio stations

The infotainment system stores all received FM radio stations in a backup memory. The radio station data list is automatically initiated when TP radio station search or the automatic radio station storage function is activated (see below). In this case, RDS radio stations are sorted in the channel list by radio station names (for example, HR1, HR2, etc.).

This list is initiated manually by holding down the “RDS” button (1) until the sound signal - the display will show “Memory FM”, then “MEM” and the operating frequency of the received radio station. To select RDS radio stations from the list, you need to briefly press the left/right sector of the 4-position switch (14) - the radio will tune to the next RDS radio station recorded in the list.

To search for RDS radio stations without using the list, it is necessary, with the RDS function activated (the corresponding indicator lights up on the display), to hold the left/right sector of the 4-position switch in the pressed position until the inscription “Seek” appears on the display - the nearest radio station transmitting RDS signals is searched for During searching, the playback sound is muted.

Comment: If the Traffic Announcement (TP) function has been previously activated (see below), the radio will only search for radio stations that support this format.

Selecting programs by message type (PTY)

Many RDS radio stations broadcast a PTY code indicating the type of program being broadcast (eg NEWS). Using the RTU code, you can search for radio stations by the type of programs broadcast.

This function is activated by selecting the corresponding parameter (PTY) in the settings menu (see above).

After each press on the upper/lower sector of the 4-position switch (14), the next/previous name of the program type will be displayed in the display field (see explanatory table). After selecting the desired type of program, you must press the right sector of the 4-position switch and hold it pressed until the inscription “RTU” appears on the display - the playback sound is turned off and the search for a radio station broadcasting a program of the specified type is activated. If the radio does not find a matching radio station, you will hear the last tuned radio station. Classification of PTY program types

Regional program search function (REG)

The REG function is activated/deactivated by pressing button (5) on the control panel of the infotainment system. When this function is activated, the corresponding indicator is displayed in the display field; when searching and selecting RDS radio stations, the regional broadcast code will be additionally checked.

Traffic messages (TP)

Reception of traffic messages is possible in the FM range, as well as when playing cassettes or CDs, regardless of the activation of the PDS function.

The sound volume level for traffic announcements can be adjusted in advance by selecting the TA VOLUME parameter through the setup menu (see above). The traffic announcement function is activated by pressing the “TP” button (4); if the currently tuned radio station does not transmit traffic announcements, the search for the radio station with the strongest signal that transmits traffic announcements is automatically activated. When the function is activated, the TP indicator appears in the display field - if messages are being broadcast, or "" - if none of the received radio stations is currently transmitting traffic information service. When receiving an information message, the audio system will automatically stop playing the current mode and switch to the frequency of the traffic message service channel and the corresponding indication will appear on the display. The transmitted information is broadcast at the volume level previously configured for traffic messages. At the end of the broadcast, the audio system will return to the previously set settings. Playback of an information message can be interrupted before the end of its broadcast by pressing the “TP” button - the audio system will return to the previously set settings, and the TP function will go into standby mode for the next message. The function is deactivated by pressing the button (4) again. Searching for radio stations broadcasting traffic announcements can be done by pressing the right/left sector of the 4-position switch in the same way as when selecting RDS radio stations (see above), but with the TP function activated.

This audio system allows you to listen to traffic messages without playing other broadcast sources or CD recordings. To do this, you need to turn off the sound by blocking (see above) - “Mute” will appear on the display, or by turning the volume control knob (8) to the extreme left position. In this case, the audio system will only play traffic announcements received at the volume level preset for this function (see above). If a source of external audio signal (for example, a mobile phone) is connected to the audio system, then when this device is operating, playback of other audio sources (including broadcasting traffic messages) is not available - “Extern In” will appear on the display screen. However, if necessary, you can interrupt the sound playback from an external source and switch to receiving a traffic message. When the TP function is activated, when a message is received, the screen will display “Extern In.” instead of “Extern In.” The name of the radio station broadcasting the traffic announcement will appear. To switch to message playback mode and back, press the “TP” button (4).

Entering preset memory

The radio receiver's memory can store up to 12 settings FM radio stations (6 each in FM and FMAS level) and up to 12 settings AM radio stations (6 each in AM and AM-AS level).

To activate the FM-AS or AMAS level, you must press the “AS” button (2) on the system control panel after pre-selecting the FM or AM band - the corresponding indicator should light up on the display. To go to the first level of the corresponding range, you must press the same button again - the indicator in the display field should go out.

Frequencies are entered into the system memory in the following sequence:

a) Perform manual tuning to the desired radio station (see above).

b) Press one of the 6 preset radio station selection buttons (12) and hold it for approximately 3 seconds until the sound signal is triggered - during this time, the frequency previously stored in this memory cell is displayed on the display screen. After a confirmation signal, the radio receiver begins broadcasting the newly tuned radio station, and the name or operating frequency of this radio station appears on the display - the setting is stored in memory.

Comment: When the button is pressed, audio playback will be temporarily stopped and will resume when the button is released.

c) Repeat the above operations with other buttons to tune in the most frequently listened to radio stations.

Comment:The frequency is stored in memory simultaneously with the RDS settings that were activated at the time of recording.

Manual tuning and recording of frequencies can also be performed when the AS level is activated. The settings stored in the memory cells are activated by briefly pressing the number buttons 1-6 (12) after first selecting the desired level using the “AS” button (2). In addition, if you hold the “AS” button (2) pressed until a sound signal is heard, the radio receiver will switch to the AS level and an automatic search for stations will be performed, and the settings of 6 of them (with the strongest signal) are stored in the receiver’s memory cells (numbered buttons (12)).

Comment:During this operation, the playback sound is muted. Entries are made for AS level only.

When you enable automatic recording of radio stations into memory, the RDS function is automatically activated - first all radio stations that support the RDS format are memorized. If, before activating the function of automatic memorization of radio stations or during memorization, you activate the function for receiving traffic messages TP (see above), then the radio receiver, after the end of the automatic search, calls the radio station that transmits traffic messages.

Comment:If the TP function is turned on during automatic recording, the automatic channel search operation remains activated until at least 1 radio station broadcasting traffic information is found.

If during a trip the car leaves the coverage area of ​​transmitting radio stations, the frequencies of which are stored in the system memory, it is necessary to reconfigure the memory cells to new radio stations.

Dear visitors!!!

If we compare outdated and modern models of radios, they of course have their differences both in design and in electrical circuits. But the basic principle radio signal reception- not changeable. For modern models of radios, only the design itself changes and minor changes are made to the electrical circuits.

As for tuning the radio receiver to the wave, receiving transmissions in the ranges for:

• long waves\LW\;
• medium waves \NE\,

- usually carried out using a magnetic antenna. In ranges:

— radio reception is received via a telescopic \outdoor\ antenna.

Figure No. 1 shows the appearance and graphic designation of receiving antennas:

telescopic;

magnetic \antenna DV and SV\.

Reception by magnetic antenna

Figure No. 2 shows a visual representation of how radio waves bend around obstacles \for mountainous areas\. The radio shadow region is represented as a zone beyond the reach of radio waves by the receiver.

What is a magnetic antenna? — The magnetic antenna consists of a ferrite rod, and the magnetic antenna coils are wound on separate \isolated\ frames. The ferrite rod of a magnetic antenna for different radios has its own diameter and length. The winding data of the coils, accordingly, also have their own specific number of turns and their own inductance - for each of these magnetic antenna circuits.

As you understand, such concepts in radio engineering as each individual magnetic antenna circuit And magnetic antenna coil, - have the same meanings, that is, you can formulate your proposal in one way or another.

In radio receivers, a magnetic antenna for DV and SV is mounted in the upper part. In the photograph, the magnetic antenna looks like an oblong, cylindrical rod made of ferrite.

If each coil \circuit\ of a magnetic antenna has its own inductance, then it is designed to receive separate ranges of radio waves. For example, according to the electrical circuit of a radio receiver, you observe that the magnetic antenna consists of five separate circuits \L1, L2, L3, L4, L5\, two of which are necessary for the received range:

• DV \L2\;
• NE \L4\.

Other circuits L1 L3 L5 are communication coils, one of which, say L5, is connected to an external antenna. This explanation is not given specifically for each circuit, because the meaning of the symbols in the circuits may change, but a general concept of a magnetic antenna is given.

Reception-on telescopic antenna

telescopic radio antenna

Depending on the radio receiver circuit, the telescopic \whip antenna\ can be connected either to the input circuits of the long and medium wave ranges through a resistor and a coupling coil, or to the input circuits of the short wave range - through an isolating capacitor. From the taps of the coils of the DV, SV or HF circuits, the signal voltage is supplied to the input of the RF amplifier.

Winding data - antennas

The winding on the circuits is made with a single or double wire. Each circuit has its own inductance. The amount of loop inductance is measured in henry. To independently rewind a circuit, you need to know the winding data of this circuit. That is, you need to know:

• number of turns of wire;
• wire section.

All the necessary technical data for outdated models of radios could be found in reference books. At this time, there is no such literature for modern models of radios.

For example, for receivers:

• Mountaineer-405;
• Giala-404,

— the winding data of the coils coincided with each other. That is, let’s say the communication coil \and there are several of them - in the diagram\ with its designation, it could be replaced from one receiver circuit to another circuit.

A circuit malfunction is often associated with mechanical damage to the wire \accidentally touching the wire with a screwdriver and so on\. When repairing a circuit \rewinding it\, the number of turns of the old wire is usually taken into account and then the same number of turns are performed with a new wire, where its cross-section is also taken into account.

In this article, we have partially gained an understanding of sound reception by a radio receiver. Follow the section, it will be even more interesting further.

Setting up a transistor receiver is, in principle, little different from setting up a tube receiver. After making sure that the low-frequency amplifier is corrected and the lamps or transistors of the receiver are operating in normal modes, proceed to adjusting the circuits. Tuning begins with the detector stage, then moves on to the IF amplifier, local oscillator and input circuits.

It is best to tune the circuits using a high frequency generator. If it is not there, then you can tune by ear, using the received radio stations. In this case, you may only need an avometer of any type (TT-1, VK7-1) and another receiver, the intermediate frequency of which is equal to the intermediate frequency of the receiver being tuned, but sometimes they are tuned without any instruments. When setting up, the Avometer serves as an indicator of the output signal.

When setting up the IF amplifier circuits in a tube receiver, when an RF generator and a tube voltmeter are used for this purpose, the latter must not be connected to the lamp grid, since the input capacitance of the voltmeter is added to the capacitance of the grid circuit. When setting up circuits, a voltmeter should be connected to the anode of the next lamp. In this case, the circuit in the anode circuit of this lamp must be bypassed with a resistor with a resistance of about 500 - 1000 Ohms.

Having finished setting up the IF amplification path, proceed to setting up the local oscillator and RF amplifier.

Contours of the NE and LW ranges. Short-wave coils (and sometimes medium-wave), unlike long-wave coils, usually do not have cores; they are most often wound on cylindrical (and sometimes ribbed) frames. The inductance of such coils is changed when adjusting the circuits, moving or pushing apart the turns of the coils.

In order to determine whether the turns should be shifted or moved apart in a given circuit, it is necessary to alternately insert a piece of ferrite and a brass (or copper) rod into the coil or bring it closer to it. It is even more convenient to perform this operation if, instead of a separate piece of ferrite and a brass rod, you use a special combined indicator stick, at one end of which magnetite (ferrite) is fixed, and at the other - a brass rod.

The inductance of the RF amplifier circuit coil should be increased if, at the points where the circuits connect, the volume of the signal at the receiver output increases when ferrite is introduced into the coil and decreases when a brass rod is introduced, and vice versa, the inductance should be reduced if the volume increases when a brass rod is inserted and decreases with the introduction of ferrite. If the circuit is configured correctly, a weakening of the signal volume at the interface points occurs when both ferrite and brass rods are introduced.

The circuits of the NE and LW ranges are configured in the same order. Changing the inductance of the circuit coil at the coupling points is carried out in these ranges by appropriate adjustment of the ferrite core.

When making homemade contour coils, it is recommended to wind a few obviously extra turns. If, when setting up the circuits, it turns out that the inductance of the loop coil is insufficient, winding up the turns on the finished coil will be much more difficult than winding up the extra turns during the setup process itself.

To make it easier to adjust the contours and calibrate the scale, you can use the factory receiver. By comparing the angles of rotation of the axes of the variable capacitors of the tuned receiver and the factory one (if the blocks are the same) or the position of the scale indicators, determine in which direction the circuit adjustment needs to be shifted. If the station on the scale of the tuned receiver is closer to the beginning of the scale than that of the factory one, then the capacitance of the tuning capacitor of the local oscillator circuit should be reduced, and vice versa, if closer to the middle of the scale, it should be increased.

Methods for checking a local oscillator in a tube receiver. You can check whether the local oscillator is working in a tube receiver in different ways: using a voltmeter, an optical tuning indicator, etc.

When using a voltmeter, it is connected in parallel with the resistor in the anode circuit of the local oscillator. If the short circuit of the capacitor plates in the local oscillator circuit causes an increase in the voltmeter readings, then the local oscillator is working. The voltmeter must have a resistance of at least 1000 Ohm/V and be set to a measurement limit of 100 - 150 V.

Checking the operation of the local oscillator with an optical tuning indicator (6E5C lamp) is also simple. To do this, the control grid of the local oscillator lamp is connected with a short conductor to the grid of the 6E5C lamp through a resistor with a resistance of 0.5 - 2 MOhm. The dark sector of the tuning indicator should be completely closed during normal operation of the local oscillator. By changing the dark sector of the 6E5C lamp when rotating the receiver tuning knob, one can judge the change in the amplitude of the generator voltage in different parts of the range. If the amplitude unevenness is observed within significant limits, more uniform generation over the range can be achieved by selecting the number of turns of the coupling coil.

The operation of the local oscillator of the transistor receiver is checked by measuring the voltage at the local oscillator load (most often at the emitter of the transistor of the frequency converter or mixer). The local oscillator voltage, at which frequency conversion is most effective, lies in the range of 80 - 150 mV on all ranges. The voltage across the load is measured with a lamp voltmeter (VZ-2A, VZ-3, etc.). When the local oscillator circuit is closed, its oscillations are interrupted, which can be noted by measuring the voltage across its load.

Sometimes it is possible to eliminate self-excitation in very simple ways. So, in order to eliminate self-excitation in the IF amplification stage, a resistor with a resistance of 100 - 150 Ohms can be connected to the control grid circuit of the lamp of this stage.

The amplification of the intermediate frequency voltage in the cascade will decrease slightly, since only a small part of the input signal voltage is lost across the resistance.

In some cases, self-excitation in the receiver and TV can be eliminated by such measures as moving the grounding of individual circuit elements, reworking the installation, etc. The effectiveness of the measures taken to combat self-excitation can often be assessed in the following way.

Rice. 25. To explain the method of eliminating self-excitation in transistor reflex receivers

The receiver or TV is connected to an regulated power source (that is, to a source whose voltage supplied to the anode circuits can be varied within wide limits), and a lamp voltmeter or other dial indicator is turned on at the output of the receiver. Since at the moment self-excitation occurs, the voltage at the output of the receiver changes sharply, the deviation of the indicator arrow makes it easy to note this. The voltage taken from the source is controlled by a voltmeter.

If self-excitation occurs at the rated voltage, then the supply voltage is reduced to a value at which generation stops. Then they take certain measures against self-excitation and increase the voltage until generation occurs, noting it on a voltmeter. If the measures are successfully taken, the threshold for self-excitation should increase significantly.

In transistor reflex receivers, self-excitation can occur due to poor placement of the high-frequency transformer (or inductor) relative to the magnetic antenna. Such self-excitation can be eliminated by using a short-circuited turn of copper wire with a diameter of 0.6 - 1.0 mm (Fig. 25).

A U-shaped wire bracket is threaded through the hole in the board, bent from the bottom, twisted and soldered to the common wire of the receiver. The bracket can serve as an element for fastening the transformer. If the transformer winding is wound uniformly on the ferrite ring, then the corresponding orientation of the short-circuited turn relative to other ferrite parts is not required.

Why does the receiver “howl” on the KB band. It can often be observed that a superheterodyne receiver, when receiving a broadcast station on short waves, begins to “howl” with a slight detuning. However, if the receiver is tuned more accurately to the station being received, reception becomes normal again.

Such generation can be eliminated by improving the damping of the tuning unit, as well as reducing acoustic feedback using various available methods - changing the method of mounting the loudspeaker, etc.

Setting up an IF amplifier using another receiver. At the beginning of this section, a method was described for tuning a radio receiver using simple instruments. In the absence of such devices, tuning radios is usually done by ear, without instruments. However, it should be said right away that this method does not provide sufficient adjustment accuracy and can only be used as a last resort.

To tune the IF amplifier circuits, instead of a standard signal generator, you can use another receiver, the intermediate frequency of which is equal to the intermediate frequency of the tuned receiver. -For a tuned tube receiver, the AGC wire running from the diode to the control grids of the adjustable lamps must be disconnected from the diode during setup and connected to the chassis. If this is not done, the AGC system will make it difficult to fine-tune the bandpass filters.

In addition, when setting up an IF amplifier, it is necessary to disrupt the oscillations of the local oscillator by blocking its circuit with a capacitor with a capacity of 0.25 - 0.5 μF.

The auxiliary receiver used in this case does not need to be subjected to any significant modifications. To set up, you only need a few additional parts: a variable resistor (0.5 - 1 MOhm), two fixed capacitors and two or three fixed resistors.

Setting up amplifier circuits. The receiver IF is produced as follows. The auxiliary receiver is pre-tuned to one of the local stations operating in the long or medium wave range. Next, the common wires or chassis of both receivers are connected to each other, and the wire going in the tube receiver to the control grid of the lamp of the first IF amplification stage of the auxiliary receiver is disconnected and connected to the control grid of the lamp of the corresponding stage of the IF amplifier of the tuned receiver. In the case of setting up a transistor receiver, the IF signal through capacitors with a capacity of 500 - 1000 pF is supplied alternately to the bases of the transistors of the corresponding stages of the IF amplifier.

When setting up the IF amplifier stages of a transistor receiver, its local oscillator should be turned off by installing a jumper in the local oscillator circuit.

After this, by applying an intermediate frequency signal from the auxiliary receiver to the input of the IF amplifier being tuned and smoothly adjusting the settings of the IF circuits of the latter, we achieve audibility of the station to which the auxiliary receiver is tuned. Then they continue to adjust each circuit separately (to the maximum signal level), and the adjustment is best done using a pointer device connected to the output of the low-frequency amplifier, or using an optical indicator (6E5C lamp or similar).

Start tuning from the last inverter circuit; the signal is supplied to the base of the corresponding transistor or directly to the grid of the lamp in the anode circuit of which the tuned circuit is included.

If the setting is carried out not according to the optical indicator, but according to the sound volume, then it is recommended to set the volume level to minimum, since the human ear is more sensitive to changes in the volume level with weak sounds.

About tuning the receiver by radio stations. Tuning a superheterodyne receiver - tube or transistor - for received stations without using an auxiliary receiver usually begins on the KB band.

By adjusting the IF circuits for maximum noise and rotating the tuning knob, the receiver is set to any of the audible stations. If it is possible to receive such a station, then they immediately begin to adjust the IF circuits, achieving maximum audibility (tuning begins with the last IF circuit). Then the heterodyne and input circuits are tuned, first at short, then at medium and long waves. It should be noted that setting up receivers using this method is complex, time-consuming and requires experience and skills.

By tuning superheterodyne receivers according to the received stations and using a 6E5C lamp as an indicator of tuning accuracy, it is more convenient to adjust the contours at an input signal level at which the dark sector of this lamp narrows to 1 - 2 mm.

To regulate the signal voltage at the receiver input, you can connect, for example, a variable resistance resistor in parallel to the antenna coil, the value of which, depending on the sensitivity of the receiver, can be selected in the range from 2 to 10 kOhm.

How to detect a faulty stage in an RF amplifier. When setting up or repairing a receiver, a cascade in which there is a malfunction can be detected using an antenna, alternately connecting it to the bases of transistors or to the grids of amplifier lamps and determining by ear by noise whether there are malfunctions in these cascades.

This method is convenient to use in cases where there are several RF amplification stages.

An antenna in the form of a piece of wire can also be used when testing the IF and RF amplification stages in televisions. Since shortwave stations often operate at frequencies close to the intermediate frequency of televisions, listening to these stations will indicate the serviceability of the audio channel,