Why radio? Characteristic signs and causes of malfunctions of receivers and radios. How to get rid of microphone effect

Currently, the electronic equipment market offers hundreds of models of radio broadcast receivers from dozens of manufacturers. How to choose the right radio receiver? This review discusses aspects of choosing the device that best suits your goals and objectives. To do this, we analyzed the technical parameters that must be taken into account when selecting the best radio receiver with good reception in your conditions.

What is a radio receiver

Radio receiver - This is a device that is capable of selectively receiving radio waves modulated by sound from the air, and isolating and reproducing this sound signal. In English, the name of such devices sounds like receiver. In addition, devices have now appeared that receive broadcasts from radio stations broadcasting not on the air, but on the Internet. They are called Internet radios.

Household terrestrial radio receivers can be classified according to several criteria:

1. According to accepted radio wave range: DV, NE, HF, .
2. By type used modulation: AM, .
3. According to the applicable tuner: , .
4. By execution: stationary, portable (portable, pocket).
5. By method nutrition: network, battery, rechargeable.

Internet radio Sangean WFR-27C:

Wave ranges of terrestrial radio receivers

Based on wavelength, radio broadcasting ranges are divided into:

1. Long wave.
2. Medium wave.
3. Shortwave.
4. Ultrashortwave.

• Broadcasting long wave range(LW) has wavelengths from 700 to 2000 m, foreign designation LW - Longe Waves. Characterized by a small dependence of the distribution on the time of day. Wave spreads over hundreds of kilometers and reaches even 1000 km depending on the transmitter power. The number of broadcast radio stations in this range is constantly decreasing due to the poorest sound quality on these waves.
• Medium waves with a length of 200 - 540 m are designated as NE, abroad MW - Midle Waves. The distribution is highly dependent on the time of day. During the day, NEs propagate in the same way as LWs. But at night the waves are reflected from the ionosphere and they can be transmitted over thousands of kilometers.
• Characteristic feature of the shortwave range HF (10-100 m) is long-range propagation. Moreover, depending on the wavelength, the waves are well reflected either during the day or at night. This range in radio receivers is usually divided into several sub-bands: two (night and day) or more. HF ranges: 90, 75, 60, 49, 40, 31 m - night; 25, 21, 19, 16, 15, 13, 11 m - daytime. Abroad, these waves are called SW - Short Waves.
• Ultrashortwave range; historically has two subranges: domestic VHF(frequencies 65.8-74 ​​MHz) and foreign FM(87.5-108 MHz), although the name of the latter reflects the name of the Frequency Modulation with which the sound is transmitted. VHF frequencies are characterized by a small amount of interference, short-range propagation and broadcasting with the best sound quality from all ranges.

Types of radio modulation

Modulation is a method by which sound is superimposed on a radio wave, which carries information over a distance. The wave itself is called “carrier”. Modulation is named according to the wave parameter that changes when sound is superimposed. For radio broadcasting, two types of modulation are used:

1. Amplitude(AM).
2. Frequency(World Cup).

• Amplitude modulation is used on LW, MW and short waves. AM is subject to strong influence of impulse noise and lightning discharges. The advantage of amplitude modulation is the narrow signal bandwidth.
• FM frequency modulation, whose name in English is Frequency Modulation (FM or FM), is used on VHF, the widest frequency range. FM radios provide the highest quality sound. However, the FM signal occupies a much wider bandwidth than AM. Therefore FM is not used on other bands.

Digital radios and analogue

There are two types of tuners used in household radio receivers:

1. Analog.
2. Digital.

• The conversion and processing of radio signals is carried out using traditional analog methods: amplification, conversion, detection. And tuning at the station is carried out in the old way - by rotating the tuning wheel.

Example of an analog device: Sangean PR-D6.

• , controlled by the processor, not only provides high frequency stability, but can also provide many convenient additional functions.

Example of a digital radio: Tecsun PL-380.

Analog radios

The circuitry of analog radio receivers is usually built according to two principles:

1. Superheterodyne reception.
2. Direct gain.
3. Direct conversion.

• A superheterodyne radio receiver converts any input signal into an intermediate frequency (IF), at which the main signal amplification is carried out. The conversion process takes place in a mixer, to which an input frequency and a signal are supplied from a local oscillator - a smooth range generator, which generates such a frequency that the sum or difference with the input signal produces an IF. Since the intermediate frequency is constant, the IF receiving path is optimized for amplification and suppression of out-of-band signals. Therefore, superheterodynes provide the best quality of radio reception.
• Direct amplification receivers typically operate on long, medium, or short wave amplitude modulation (AM). They have simpler circuitry and, accordingly, lower cost. However, all amplification occurs at audio frequencies and at the input frequency, which varies depending on what radio station we are receiving. Therefore, the variable frequency path cannot be as optimized as the IF of superheterodynes. Direct amplification devices have lower sensitivity and selectivity - the ability to receive a selected radio station in the presence of a powerful station at adjacent frequencies.
• Direct conversion is often used in simple FM radio receivers. The conversion of the modulated high-frequency signal into audio frequencies occurs directly at the local oscillator frequency or at its second harmonic, and the automatic frequency control (AFC), which provides synchronous adjustment, is controlled directly from the audio signal. In terms of simplicity of circuit design, direct conversion receivers are comparable to direct amplification devices, but provide better technical characteristics compared to them.

Manufacturers of radio receivers currently prefer not to indicate by what scheme the receiving part is assembled. And it is impossible to say with certainty about a specific device without seeing its diagram that it is a superheterodyne, direct amplification or direct conversion. However, you can be sure that inexpensive receiving devices are not superheterodynes.

Technical characteristics of radio receivers

The main technical characteristics of radio receivers include:

1. Sensitivity.
2. Adjacent channel selectivity.
3. Mirror channel selectivity.
4. output power.
5. Current consumption.

• Sensitivity shows the weakest signal this device can receive. Voltage sensitivity is measured in microvolts (µV), and field strength sensitivity is measured in millivolts per meter (mV/m). The lower these values, the weaker the radio station the radio can reproduce.
• Adjacent channel selectivity determines the ability to qualitatively receive a useful signal in the presence of a powerful interfering radio station at an adjacent frequency. The suppression of the adjacent channel in good devices reaches millions of times, so selectivity is expressed in logarithmic units - decibels (dB). The higher the value, the better the selectivity. For good receivers it is above 60 dB and reaches 100 dB.
• Selectivity along the mirror channel is characteristic only of superheterodynes. It is similar to the parameter described above, but the interfering signal is not at the adjacent frequency, but at the mirror one. The mirror receiving channel is formed due to the fact that in the mixer the input frequency is converted not only in the sum with the local oscillator frequency, but also in the difference. High-quality input circuits highlight the useful signal and suppress the mirror reception channel. This characteristic is also measured in decibels.
• Power output indicates how loud the sound can be expected from a given sample. Power is measured in Watts (W) or milliWatts (mW). Stationary devices are characterized by output power values ​​of several Watts or tens of Watts, pocket devices - hundreds of milliWatts, and portable devices - 1 or several Watts. The higher the output power value, the louder the sound.
• Current consumption is important for battery or rechargeable samples. It allows you to calculate how long the battery charge will last. Current is measured in Amperes or milliamps. A lower current will ensure longer operation of the device.

Since household radio receivers are not currently subject to mandatory certification, manufacturers of these radio receivers, at best, indicate only the sensitivity, output power and current consumption of radio receivers.

Advantages of digital radios

The presence of a processor in digital radios allows for additional advantages:

1. Frequency stability.
2. Auto search channels.
3. Memory buttons channels.
4. Clocks, alarms, sleep timers.
5. System Radio Data System(RDS).
6. Working with external and flash cards .

• The digital synthesizer provides the highest frequency accuracy and stability of tuning to the radio station.
• The search for radio stations can be carried out in two modes: manual and automatic, with the frequencies of the found stations being recorded in memory cells.
• Favorite radio stations can be stored in the memory buttons and selected with one click.
• Not only does a clock radio allow you to know the exact time, but many models can turn the device on or off at a given time, using it as an alarm clock. And also use a timer to turn off the device if no button has been pressed for a long time.
• RDS system receives and displays text information transmitted digitally by a broadcast radio station simultaneously with sound.

For example, a radio with RDS - Eton Traveler III.

• A digital radio with a USB port can play common audio formats, such as MP3.
• USB flash drives plugged into a USB port or SD cards placed in a special slot are usually used as external drives.

Portable portable and stationary radios

Radio receivers are divided into several groups according to the place of use:

1. Stationary.
2. Portable (portable).
3. Pocket.

Network and battery-powered radios

According to the method of power supply, broadcast receivers are divided into:

1. Rechargeable.
2. Battery.

• Network devices are powered by a fixed AC network and, as a rule, have a built-in power supply. However, such models may also have a separate power adapter.

In the photo there is a radio with mains power - BZRP RP-301.

• Rechargeable radios are powered by a built-in rechargeable battery (AB), which can be charged using a built-in charger or an external one.

Example - model with built-in battery Lira RP-260-1:

• Battery radios operate on replaceable batteries, which can be of different sizes for different device models: A, AA, AAA, AAAA, B, C, D. The most commonly used battery cells, the so-called “finger-type” batteries, are of size AA (diameter 14.5 mm , length 50.5 mm). They have been produced for over 100 years, since 1907. Typically, any battery receiver can be powered by batteries of the appropriate size. If the design does not provide for charging such a battery, then you can use an additionally purchased external charger.

Often the manufacturer produces radio receivers with combined power supply:

• Battery powered and mains powered.
• From the network, batteries and batteries.

Internet radios

Internet radios occupy a separate niche because:

1. They have wider functionality than ethereal ones.
2. Provide high quality playback, regardless of location.
3. Requires a constant connection to the Internet.

For devices of this class, the main method of connecting to the Internet is Wi-Fi:

For example, Sangean WFR-29C stereo internet radio:

• . Most models have the ability to play MP3 audio files from USB drives or flash cards.
  

In the photo - an Internet radio receiver with a USB input Sangean WFR-28C:

Review of popular radio brands

Currently, broadcast receivers from dozens of different manufacturers are offered on the electronics market. Let's consider brands of manufacturers offering products at affordable prices and with good quality.

Sangean radios

The Taiwanese company Sangean was founded in 1974 and has headquarters in New Taipei and offices in the Netherlands and the USA. Production is located in China. Sangean offers the widest range of radio receivers with excellent quality. Let's look at the most interesting models:

• Sangean ATS-909X and ATS-405 high-end all-wave radios
• FM stereo receiver Sangean PR-D5
• Sangean PR-D7 clock radio
• Receiver with remote control Sangean WR-2
• Internet radio with Wi-Fi Sangean WFR-27C

Lyra radios

The domestic manufacturer Izhevsk Radio Plant (IRZ) produces radio receivers under the Lear brand. Russian radios are distinguished by good quality, compliance with GOST standards and low price. The most successful examples:

• Digital FM radio Lyra RP-248
• Retro style stationary receiver Lyra RP-249
• Desktop device Lyra RP-236
• Portable radio Lyra RP-234-1.

Tecsun radios

The Chinese company Tecsun, founded in 1994, focuses on the production of VHF, HF and MF radio broadcast receivers. Some manufactured models are borrowed from Eton. The most interesting examples of products:

• Digital radio receiver Tecsun PL-380
• Porenosny model Tecsun PL-360
• Model with two speakers Tecsun PL-398MP
• Clock radio Tecsun PL-310.

Perfeo radios

Another Chinese manufacturer, Onyx International, specializes in producing e-books under the Onyx brand. Radio receivers for sale in Russia are produced under delusion

The editorial office of OG constantly receives calls from readers regarding the disconnection of radio points (network, also known as wired radio) and radio broadcasting on long and medium waves. People, mostly elderly, are worried about what is happening and do not know how to hear the usual “Radio Russia” and “Mayak” now.

For many residents of our country and region, these radio stations have been the main, and sometimes the only way to obtain information for many years. Together with the radio, they fell asleep and got up, did morning exercises, “read” books and “watched” plays. Just imagine - in 1962 there were about 48 million radio points in the USSR!

Igor Bulygin, Chairman of the Veterans Council of the Radio Equipment Plant, shows one of the popular radio receivers in the past. Photo: Alexander Isakov

Radio used to teach, for example, I learned Russian by listening to wonderful announcers - Moscow and our local ones, they always had very competent speech, and it was cultural - there were radio concerts, theater performances, you could sit and listen with the whole family, - recalls Boris Koshelev, senior researcher at the Popov Radio Museum in Yekaterinburg.

However, over the past few years, everything has changed: first, “Mayak” fell silent on medium waves, soon “Radio Russia” fell silent on long waves, and network radio, where “Radio Russia” also sounded, was gradually switched off. Not understanding what is happening, people take their receivers for repairs, but the technicians there are unable to help them - the receivers are in good working order... Radio listeners also contact city administrations, but local officials also shrug their shoulders.

By the waves

The shutdown of radio broadcasting on medium and long waves occurred by decision of the broadcaster - the All-Russian State Television and Radio Company. The main reason is the high cost of using long-wave and medium-wave bands, when there are more economical and modern options, for example, broadcasting in FM and VHF*. Therefore, throughout the country on March 14, 2013, Radio Mayak went silent on medium waves, and on January 9, 2014, Radio Russia went silent, and, accordingly, the local airwaves also disappeared. A lot of time has passed, but people are still trying to find answers to the questions: what happened and will the radio talk again? The Urals even addressed this to Tatyana Merzlyakova, Commissioner for Human Rights in the Sverdlovsk Region.

VHF range - 65.9-74 MHz, FM range - 87.5-108 MHz

There are a lot of appeals, collective letters are received from some districts of the region, for example, from Baikalovsky and Novolyalinsky. We made a request to Moscow, the Ministry of Communications of the Russian Federation answered that radio broadcasting on long and medium waves is yesterday, we need to move on. But I believe that the country should have a single information space, only then can it be considered strong,” said Tatyana Merzlyakova.

She also promised not to abandon this issue. Tatyana Merzlyakova has already agreed to unite human rights commissioners from several regions of the country to find a solution to this problem. By the way, technically the Sverdlovsk branch of the Russian Television and Radio Broadcasting Network is ready to resume long-wave broadcasting to the Sverdlovsk region at any time - the radio station was not destroyed, its work was simply suspended.

The network is unprofitable

Network radio broadcasting is not turned off everywhere at once, but in the event of a breakdown or break, the network is no longer repaired. For example, residents of Polevsky faced this problem:

Our radio station has not been working for two years now. I contacted the head of Polevsky’s administration, and from there I was redirected to the regional government. “I only found out that when the Internet was installed in our house, the transmitter was damaged, but no one is going to fix it,” she said pensioner Inessa Popova.

According to a representative of the operator company responsible for wired radio, repair work is too expensive - the costs of restoring and upgrading the network are not comparable to the profit. And there are fewer and fewer subscribers every year. If earlier there were a hundred radio points on one line and there was a subscription fee for each (about 100 rubles per month), then today there can only be 10-15 points on the same line, and the costs of maintaining the line remain the same.

Nowadays, many people themselves refuse radio points, so it is unprofitable to maintain networks. Network breaks occur during various repair work; during major renovations of a house, the transmitter is often simply dismantled, and in new buildings radio points are no longer supposed to be installed at all,” she said Ekaterina Nechaeva, public relations specialist at Ros-Telecom in Yekaterinburg.

At the beginning of 1996, there were 1,420,000 radio points in the Sverdlovsk region, today there are only about 280 thousand, and there are ten times fewer subscribers.

It's time to change the range

What should radio listeners do, especially from remote areas of the region, where the radio signal distributed through modern technologies is not always available?

There are options for solving this problem. The press service of the Sverdlovsk branch of RTRS told us that Radio Russia is now broadcast in the VHF range throughout the entire region, the signal quality is not always ideal, but it is still possible to catch it (see diagram). To do this, you need to purchase a receiver whose scale starts at 65 MHz. It is also planned that this radio station will appear in the FM range, but the exact timing is unknown. Radio "Mayak" can be heard so far only in Yekaterinburg on the frequency 100.8 FM.

Frequencies on which Radio Russia broadcasts in various areas of the Sverdlovsk region. For example, if you are in Irbit, the closest radio antenna to you will be in Zaykovo, and the radio should be tuned to 66.83 MHz.

In addition, residents of the region can listen to the Mayak and Radio Russia radio stations via the Internet or as part of the first digital television multiplex, which is broadcast in the public domain. To receive the signal, you need a UHF antenna, a digital TV of the DVB-T2 standard or an analog TV with a digital set-top box of the same standard. True, in this case the broadcast will be only Moscow - local inclusion is not expected.

Today, the signal coverage of the first multiplex is 78 percent of the population of the Sverdlovsk region. By the end of 2016, when the construction of the broadcasting network of the first multiplex is completed, the television and radio channels of the RTRS-1 package will become available to 98 percent of residents of the region, she commented Natalya Bulatova, public relations specialist at the Sverdlovsk branch of RTRS.

However, these options are not always acceptable, especially for older people. A good radio receiver costs at least a thousand rubles, but not everyone can understand RTRS-1 digital packages and find radio stations in them without outside help.

Important

Natalya Zyryanova, head of the press service of the Main Directorate of the Ministry of Emergency Situations for the Sverdlovsk Region:

Previously, one of the most important tasks of network radio was informing the population in case of emergency. Currently, not only radio is used for this, but all resources are used to the maximum. The notification will take place through the media; we have signed an agreement on this with many local companies. There is an agreement with a number of mobile operators, and citizens are already receiving messages even in unfavorable weather conditions. In the capital of the Urals there is also an all-Russian comprehensive public warning system. This is the use of large screens in shopping centers, train stations, and airports. So-called door-to-door visits and sound alerts from cars are also used.

How to find a fault in the receiver?

The most reliable, although in some cases rather slow, way of finding a fault in receivers is to test the receiver in separate stages. To do this, the receiver is divided into separate stages that can operate independently, and each such stage is tested separately. For example, low frequency amplification is tested by connecting a gramophone adapter to the input of the low frequency amplifier; The detector lamp is tested in the same way using an adapter. A detector lamp can be tested by connecting the antenna directly to the lamp's grid circuit, bypassing the high-frequency stage. When you are confident that the low frequency stages and the detector lamp stage are working properly, then you need to connect the high frequency stage and test the receiver with this stage. If in this case the receiver does not work, then it is obvious that the fault is in the high frequency stage. By following this principle, dividing the receiver into separate operable parts and testing each part separately, you can always find a fault relatively easily.

How to make a simple damage finder?

The simplest damage detector (breaks in windings or short circuits in parts or parts of the circuit) can be assembled according to the diagram shown in the figures. To assemble the “finder” you need: a battery, a flashlight bulb and ordinary telephone handsets.

The metal-tipped ends of the cord are connected to the ends of the circuit under test. If the circuit is not damaged, the light will light up or a click will be heard in the phone. A finder with a light bulb is used when the resistance of a given circuit or part is low, but testing circuits of parts with high ohmic resistance should be done only with a telephone.

Is it a problem with the receiver that it is picking up harmonics from local stations?

The harmonics (see question 216) emitted by some transmitting stations differ from the normal fundamental frequency only in being less powerful. Therefore, the receiver receives equally well both the fundamental frequency of the station and its harmonics. Modern transmitters take every precaution to prevent the emission of harmonics, or at least to significantly reduce their power.

Why does a spark jump between the ground wire and the ground terminal when the ground is turned on?

To reduce the background of alternating current and interference coming from the electrical network, a filter consisting of two series-connected capacitors that block the lighting network is installed at the entrance to the rectifier part of amateur radio receivers (see questions 229, 230). The “midpoint” of the capacitors is grounded. When the earth is connected to the receiver, the network closes through the capacitor, as a result of which a spark jumps. This phenomenon does not pose any danger to either the receiver or the network.

What causes the “microphone effect” in the receiver?

The “microphone effect” in the receiver appears due to the fact that the vibrations that accompany the operation of the loudspeaker are transmitted through the walls of the box, and sometimes directly through the air to the receiver. In this case, some parts of the receiver may begin to vibrate. If this vibration leads to a change in any electrical properties of the receiver or its individual parts, then the entire installation begins to “howl.” Lamp electrodes, as well as variable capacitors, are most susceptible to vibration if their plates are made of thin and elastic material and do not have appropriate fastenings.

How to get rid of microphone effect?

There are two ways to get rid of the microphone effect:

1) move the loudspeaker far enough from the receiver so that the vibrations that accompany the speaker cannot affect the receiver;

2) dampen those parts of the receiver whose vibration leads to a microphone effect.

These parts, as stated in question 408, are lamps (usually a detector lamp) and variable capacitors. Vibration of lamp electrodes causes changes in lamp parameters; vibration of variable capacitors causes a change in receiver tuning. To prevent the occurrence of a microphone effect, the lamp panels are attached with elastic bands or springs to the receiver panel so that vibrations of the receiver chassis are not transmitted to the lamp. Usually it is sufficient to dampen only the detector lamp, but in some cases it is also necessary to dampen the receiver's variable capacitor assembly. To do this, the capacitor assembly is installed on some metal frame, and the frame is softly fastened to the receiver chassis panel. Rubber is also used to cushion the units.

Why does the receiver setting change when adjusting the volume in cases where the volume control is at the receiver input?

There are two reasons for changing the setting. One reason that is observed when adjusting the volume using a variable capacitor is that when the capacitance of the antenna capacitor changes, the capacitance of the antenna circuit, which in the circuit is connected in parallel with the circuit tuning capacitor, changes within certain limits. In addition, with any scheme for adjusting the volume at the receiver input, a change in the setting occurs due to the fact that any volume adjustment ultimately comes down to a change in the connection of the first circuit of the receiver with the antenna, as a result of which the amount of detuning that is introduced from the antenna also changes to the first circuit.

Within certain limits, changing the tuning of the primary circuit when adjusting the volume can only be eliminated by significantly weakening the connection between the primary circuit and the antenna. Achieving a minimum change in the settings of the first circuit when adjusting the volume can only be done by choosing the correct circuit and type of connection between the receiver and the antenna.

Why is the reception accompanied by crackling sounds?

It is very difficult to get rid of crackles coming from the ether. Often radio listeners who have just acquired a receiver, or novice radio amateurs, tend to first of all look for the cause of crackling in the receiver itself. You can find out the real cause of the crackling in a fairly simple way - compare the quality of simultaneous operation of your receiver under the same conditions with another that is known to work well. If it turns out that the crackles are caused by the receiver, then this may be a consequence of poor contacts and connections of the wires to each other, loose contact of the lamp legs in the sockets, etc. If the crackles are heard only when tuning the receiver and in certain areas of the scale, then this suggests that that short circuits occur in the plates of variable capacitors.

What is the reason for “machine gun fire” when the receiver is operating?

The reasons that cause cod sounds in the receiver, reminiscent of “machine gun fire,” may be the following:

1) damage to the mesh leakage,

2) poor feedback regulation,

3) poor quality of the inductor located in the anode circuit of the detector lamp. By replacing the choke with another, and if a low-frequency transformer is used as a choke, then by reconnecting the ends of the windings, it is possible to eliminate the “machine gun fire” that occurs in this case.

What needs to be changed in the circuit if the high-frequency lamp is damaged and there is no spare?

The easiest way is to connect the antenna directly to the detector circuit, but this significantly reduces the selectivity of the receiver. In order for the selectivity of the receiver not to change, it is necessary to pass high-frequency oscillations from the high-frequency circuit into the detector circuit. This is practically easy to do by connecting the wire going to the anode of the high-frequency lamp (to the pin on the cylinder) with the grid socket of the same lamp through a capacitor with a capacity of 100-150 cm (see figure). The reception volume with such a “replacement” of the lamp with a capacitor, of course, decreases, but is sufficient for receiving powerful radio stations through the loudspeaker.

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

• AM and FM radio broadcasts
• Cordless phones
• Wireless network
• Radio-controlled toys
• TV shows
• Cell Phones
• GPS receivers
• Amateur radio
• Satellite connection
• Police radio
• Wireless watches

The funny thing is that, at its core, radio is an incredibly simple technology. With just a few electronic components that cost no more than a dollar or two, you can create simple radio transmitters and receivers. The story of how something so simple became the core technology of the modern world is fascinating. In today's article, we will look at a technology called radio, so that you can fully understand how invisible radio waves make so many things and make our lives easier.

The simplest radio

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

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

More complex radio

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

Radio Basics: Parts

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

Radio Basics: Real Examples

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

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

A typical baby monitor with a transmitter on the left and a receiver on the right. The transmitter is located directly in the child’s room and serves as a kind of mini-radio station. Parents take a receiver with them and use it to listen to the child’s actions. Communication range is limited to 200 feet (61 meters)

Don't worry if terms like "modulation" and "frequency" don't make sense to you now - we'll get to them in a while and I'll explain what they mean.

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

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

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

Simple transmitters (transmitters)

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

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

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

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

Transfer of information

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

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

Amplitude modulation- Both AM radio stations and part of the television signal signal amplitude modulation to encode information. In amplitude modulation, the amplitude of a sine wave (its voltage from peak to peak) changes. So, for example, the sine wave produced by a person's voice is superimposed on the transmitter's sine wave to change its amplitude.

Frequency modulation- FM radio stations and hundreds of other wireless technologies (including the audio portion of television signals, cordless phones, cell phones, and so on) use frequency modulation. The advantage of FM is that it is largely immune to static. In FM, the change in frequency of the transmitter's sine wave is very loosely based on the information signal. Once you have modulated a sine wave with information, you can transmit it!

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

AM signal reception

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

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

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

Antenna Basics

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

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

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

Antennas: real examples

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

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

“Radio in the 21st century? Maybe we can also connect a telegraph?” - you ask a reasonable question. Many people think that radio is outdated a long time ago, and they simply don’t understand what it is needed for. But in fact, radio has a number of advantages:

1. Latest news. Often not in the typical dry and dull presentation of television.

2. Favorite music. Yes, of course, in our time, when you can plug in a flash drive and listen to your favorite songs without advertising, radio stations are morally outdated. However, radio is good for its variety and randomness, which means that your favorite music will be a pleasant surprise every time.

3. Informative function. So, for example, if suddenly some mad general launches all the missiles at your city or the aliens want to implant probes into every inhabitant of the Earth, then you will be one of the first to know about it on the radio. And while the rest of the planet’s inhabitants will painfully solve the dilemma: run into the forest or cooperate with the reptilians, you will have time to hide in your bomb shelter.

In addition to ordinary radios, which perform only one function - playing music, there are also clock radios, which, like in American films, instead of an alarm clock, turn on music or the speech of a cheerful DJ, which is clearly better than simple beeping. Most often, radios are used as speakers for playing music from a flash drive, which is convenient, for example, on trips to nature or on hikes, and a clock radio is a practical device for use in everyday life that perfectly complements the interior.

In this article we will talk about several radios from the Ritmix company that will decorate your bedside chest of drawers.

Ritmix RPR-171

Ritmix RPR-171 is a classic form factor in the style of the 90s. The radio is made of plastic and has dimensions of 165x73x115 and a weight of only 742 grams, so you can even take it with you in a backpack if you decide to go outdoors with friends. Ritmix RPR-171 operates in the FM/AM/SW frequency range and has a telescopic antenna to improve sound quality. By the way, the ability to listen to AM and SW frequencies is a rather rare feature these days. The radio has a built-in USB input for flash drives, as well as slots for SD and MMC memory cards. The front panel features a full-range speaker, radio station and volume controls, and a '90s-style station dial. On the top edge there is an equalizer setting, control buttons and frequency switching. There is also a 3.5 audio input and an AUX input.

Ritmix RRC-1212

Ritmix RRC-1212 is the clock radio mentioned above. Externally, this cool device corresponds to a modern design in a minimalist style and is suitable for creating a futuristic environment. This small rectangle has several useful features. For example, the Ritmix RRC-1212 clock radio has a bright display with numbers 3 centimeters high, so whether late at night or in the middle of the day you will be aware of the time. Ritmix RRC-1212, unlike the previous model, operate only on FM frequencies 87-108 MHz with digital tuning to 20 stations. The most useful feature of a clock radio is that it has two alarms with a snooze function, so you won't oversleep. Ritmix RRC-1212 also has a shutdown timer. The clock radio operates from the network. Saving the current settings is ensured by two AAA batteries. Switching stations and setting the alarm clock is done using the keys on the top edge of the Ritmix RRC-1212.

Ritmix RRC-1810

Ritmix RRC-1810 is a more advanced clock radio. Ritmix RRC-1810 differs from the previous model by an even larger display, on which the height of the numbers is 4.5 centimeters. The clock radio has an external antenna for improved sound quality. Ritmix RRC-1810 operates in the FM frequency range 87-108 MHz, which covers all popular radio stations. The clock radio also has digital tuning to 20 stations. And, of course, a clock radio wouldn’t be a clock radio if it didn’t have an alarm clock built into it, and this model has two of them. Well, if you decide to sleep longer, ignoring the signal, then the Ritmix RRC-1810 has a repeat alarm. In addition, the clock radio has a shutdown timer. The Ritmix RRC-1810 is controlled using large buttons on the top edge.