VHF receiver with extended range. Extended range digital radios Extend fm coverage

So, with reasonable care, we open the device. We look at what the frequency tuning knob is connected to. It can be a variometer (a metal thing a few centimeters long, usually there are two or one double, with longitudinal holes into which a pair of cores are pushed in or out.) This option was often used before. Until I write about it. () And it may be a plastic cube a few centimeters in size (2 ... 3). It contains several capacitors that change their capacitance at our whim. (There is also a varicap tuning method. At the same time, the tuning control is very similar to the volume control. I have not seen such an option).

2. LET'S FIND THE HETERODYNE COIL AND THE CAPACITORS CONNECTED TO IT.

So, you have KPE! We act further. We are looking for copper coils around it (yellow, brown spirals of several turns. Usually they are not even, but crumpled and tumbled awry. And that's right, they are tuned that way.). We can see one, two, three or more coils. Don't be scared. Everything is very simple. We turn on your device in disassembled form (do not forget to connect the antenna more authentically) and tune it to any radio station (better not to the loudest one). After that, we touch it with a metal screwdriver or just with a finger (contact is optional, just swipe something near the coil. The reaction of the receiver will be different. The signal may become louder or interference may appear, but the coil we are looking for will give the strongest effect. It will immediately slip in front of us several stations and the reception will be completely disrupted. So this is what a HETERODYNE coil is. The frequency of the local oscillator is determined by a circuit consisting of this very coil and capacitors connected in parallel to it. There are several of them - one of them is located in the KPI and controls the frequency tuning (we use it to catch different stations), the second is also in the KPI cube, or rather on its surface. Two or four small screws on the back of the KPI (usually facing us) are two or four trimmer capacitors. One of them is used to adjust the local oscillator. Usually these capacitors consist of two plates that collide with each other when the screw is rotated.When the top plate is exactly above the bottom, then capacity is maximum. Feel these screws with a screwdriver. Move them back and forth a few (as little as possible) degrees. You can mark their initial position with a marker to insure against trouble. Which one affects the setting? Found? We will need it in the near future.

3. ONCE AGAIN, LET'S DECIDE WHERE WE ARE RESTRUCTURING AND ACT.

What range is in your receiver and what is needed. Do we lower the frequency or increase it? To lower the frequency, it is enough to add 1 ... 2 turns to the heterodyne coil. As a rule, it contains 5 ... 10 turns. Take a piece of bare tinned wire (for example, a lead from some long-legged element) and put a small prosthesis. After such a build-up, the coil must be adjusted. We turn on the receiver and catch some station. No stations? Nonsense, let's take a longer antenna and turn the tuning. Here's something caught. What is this. You'll have to wait until they say or take another receiver and catch the same thing. See how this station is located. At the right end of the range. Need to move even lower? Easily. Let's move the turns of the coil tighter. Let's pick up that station again. Good now? It only catches badly (the antenna needs a long one). Right. Now let's find the antenna coil. She's around somewhere. Wires from KPE must be suitable for it. Let's try turning on the receiver to insert it into it or simply bring some kind of ferrite core to it (you can take the DM choke by removing the winding from it). Has the reception volume increased? Exactly, it's her. To reduce the frequency, it is necessary to increase the coil by 2 ... 3 turns. A piece of hard copper wire will do. You can simply replace the old coils with new ones containing 20% ​​more turns. The turns of these coils should not lie tightly. By changing the stretch of the coil and bending it, we change the inductance. The denser the coil is wound and the more turns it has, the higher its inductance and below will be the operating range. Keep in mind that the actual inductance of the loop is higher than the inductance of a single coil, as it adds up to the inductance of the conductors that make up the loop.

For the best reception of the radio signal, it is necessary that the difference in the resonant frequencies of the heterodyne and antenna circuits be 10.7 MHz - this is the frequency of the intermediate frequency filter. This is called the correct pairing of the input and heterodyne circuits. How to provide it? Read on.

ADJUSTMENT (COUPLE) OF THE INPUT AND HETERODYNE CIRCUIT.

FIG.1. The high-frequency part of the VHF-FM radio receiver board. It can be clearly seen that the input circuit trimmer capacitor (CA-P) is set to the minimum capacitance position (unlike the heterodyne trimmer capacitor CG-P). The accuracy of setting the rotors of trimmer capacitors is 10 degrees.

The local oscillator (LG) coil has a large hole in the winding, which reduces its inductance. This gap appeared during the setup process.

Another coil is visible at the top of the photo. This is the input antenna circuit. It is broadband and does not rebuild. The telescopic antenna is connected precisely to this circuit (through a transition capacitor). The purpose of this circuit is to remove gross interference at frequencies much lower than the operating ones.

AND ONE MORE ACTION SINCE WE ARE ALREADY HERE.

Tune in to your favorite station, then shorten the antenna as low as possible when the interference starts and adjust the IF filter, which looks like a metal square with a purple circle (in the middle left of the photo). The fine tuning of this circuit is very important for clear and loud reception. The slot setting accuracy is 10 degrees.

About ten ... twelve years ago, articles on the restructuring of imported receivers with the FM band (88 ... 108 MHz) to the VHF-1 range (65.8 ... 75.0 MHz) were often published in amateur radio magazines. At that time, broadcasting was carried out exclusively in the VHF-1 band.

Now the situation has changed dramatically. The air in the range of 100 ... 108 MHz is filled almost everywhere. On sale there are many imported and domestic radio receivers with a VHF-2 range or with common ones (VHF-1 and VHF-2).

Since the VHF-1 range was actually "orphaned", a giant fleet of old radios and radio tape recorders remained "out of work". You can give them a second life by relatively simple modification of the VHF units of these receivers. In doing so, the following points should be noted. Modification of inexpensive portable receivers ("VEF", "Sport", "Sokol", "Ocean", etc.) should be minimal and provide reception of 3 ... 7 VHF-2 broadcasting stations in the region. For stationary devices of a higher class with an external VHF antenna, it is desirable to keep all its technical parameters (sensitivity, local oscillator stability, wide scale, etc.).

Usually, the VHF radio receiver unit contains an input circuit, 1-2 UHF cascades, a local oscillator, a mixer, and IF cascades. As a rule, these are 4 (less common 5) LC circuits. Having a basic (even better, mounting) diagram of a radio receiver, it is easy to determine all the necessary nodes (inductors, capacitances, etc.). The first circuit of the IF and all subsequent cascades do not need to be altered.

It is clear that for the range of 100 ... 108 MHz, the capacitances and inductances of all LC circuits of the VHF-1 unit must be reduced. Theory and practice state that the capacitance of the circuit changes in proportion to the wavelength, and the number of turns of the inductor - the square root of this value.

When moving from the VHF-1 range to the VHF-2 range and with constant inductances (the number of turns of the inductors does not change) - this is an option for portable receivers for medium frequency ranges (69.0 MHz and 104.0 MHz) - we obtain the following relationship for containers:

With UKV-2 \u003d 0.44 * With VHF-1.

With this in mind, in practice the following ratio of capacities is more suitable:

With UKV-2 \u003d (0.3 ... 0.35) * With VHF-1.

In addition, in VHF units, it is possible to change the inductance of the loop coils within certain limits by rotating the tuning cores. Usually, the local oscillator of the VHF-2 block for the range of 100 ... 108 MHz should be tuned within 110 ... 119 MHz (with a margin) at IF = 10.7 MHz, and within 106 ... 115 MHz at IF = 6, 5 MHz, i.e. above the signal frequency. On the circuit diagram of the VHF-1 block, we mark those capacities that will be completely soldered from the circuit, as well as those capacities that will be replaced by others with a lower rating. Usually these are miniature disk ceramic capacitors.

Capacitors must be selected in advance, cleaned and tinned, shortening them to a minimum. If there is no device for accurately measuring capacitance, the table below will partially help to solve the problem, where the size and color of the capacitor will suggest the limits of the nominal capacitance.

Table 1

For clarity, you can compare the capacitance ratings in the "VEF-221" and "VEF-222" radio receivers, which are built according to the same circuits with the same inductors ("VEF-221" has a range of 87.5 ... 108 MHz, " VEF-222" - 65.8...74.0 MHz). These data are taken from the factory operating manual (Table 2). Capacitance ratings are given in it in picofarads.

table 2

Similar schemes of VHF units are used by the VEF-215 radio receiver and the VEF RMD-287S radio receiver, so the data in Table 2 are also suitable for reworking the VHF units of these devices.

Another example is a removable auto-receiver of the Ural-auto-2 type (input circuit, two UHF stages on GT322A transistors, a local oscillator on a microcircuit of the 224th series with the ZHA1 or XA1 index). In the input circuit in the capacitive divider C1-C2, we change C1 \u003d 22 pF by 5.1 ... 6.8 pF, C2 \u003d 33 pF - by 10 ... 12 pF. Capacitors C5, C7 and C14 of 33 pF each (series capacitances with KPI of the 1st, 2nd stages of UHF and local oscillator) are changed to 12 ... 13 pF. In the local oscillator circuit, the tuning core made of ferrite (0 2.88 mm) is changed to brass with a thread (diameter 3 mm). Another example is the tuner "Radiotechnika T-101-stereo" (VHF unit on transistors KT368A and KT339A, restructuring - varicaps KVS111A). Parallel capacitances SZ = 15 pF (input circuit), C14 = 15 pF (UHF), C18 = 9.1 pF (local oscillator) are dismantled. Serial capacitances C4 = 130 pF, C13 = 130 pF (input circuit and UHF) are changed to 43 ... 47 pF, and C15 = 82 pF (local oscillator) - to 27 ... 33 pF. To stretch the scale, we carefully unsolder the loop coil of the local oscillator and unwind 1.5 turns from the top of the coil, 1 turn from the bottom (the tap from 0.9 ... 1.2 turns as it was). Then carefully solder the coil into place.

It is convenient to divide the process of alteration of blocks of VHF receivers into several stages.

1. We provide access to the VHF unit both from the side of the parts and from the side of the printed conductors by removing the covers of the receiver and the VHF unit.
2. We determine the LC circuits of the input circuit, UHF, local oscillator, mixer, and the first circuit of the IF (the last alteration does not apply).
3. Carefully unsolder the containers to be replaced and dismantled.
4. We solder new containers prepared in advance (with cut and tinned leads) for each individual circuit of the VHF unit.
5. After making sure that there are no errors, and the circuit is not broken (there are no bad solderings, short circuits of printed tracks, etc.), turn on the power of the receiver and try to hear at least one powerful (in this place) VHF station. At the same time, we rotate the receiver tuning knob and the local oscillator core. It is very useful to have an industrial receiver with a VHF-2 range nearby. This will help to immediately identify the desired station in the tuned receiver. Having heard at least barely the station, the tuning cores of the coils and the tuning capacitors of the input circuit, the UHF and the mixer achieve a loud reception of this station. At this stage, you can determine whether you need to change the cores from ferrite to brass and vice versa.
6. By rotating the core of the local oscillator coil, we set the required place for this station on the receiver scale (focusing on an industrial receiver with a VHF-2 range). Usually, the section of the scale of the tuned receiver, where the stations of the range 100 ... 108 MHz are located, occupies a very small part of the constructive scale of the receiver (about one third).
7. We carry out conjugation of the circuits of the input circuit, UHF and the local oscillator of the tuned VHF unit. In the area near 100 MHz, we achieve the highest volume of the stations by rotating the tuning cores of the input circuit, UHF and mixer, and in the area near 108 MHz - by rotating the rotors of the tuning capacitors of the same cascades (in this case, you need to monitor the position of the receiver tuning knobs - the maximum capacity of the KPI or varicaps at the beginning of the range and their minimum capacity at the end). We repeat this operation 2-3 times. In conclusion, it is necessary to reduce the capacitance in the AFC circuit by 2 ... 2.2 times (if its value exceeds 5 ... 6 pF). The last stage must be carried out in the assembled VHF unit through the holes in the covers to adjust the capacitances and inductances with a dielectric screwdriver.

These general rules for reworking VHF units should be followed for various schemes and designs of units. Briefly about receiving antennas. Obviously, directional antennas provide excellent reception quality, but they need to be rotated. The author uses a single square for the rebuilt tuner "T-101-stereo" (in parallel, two copper wires with a diameter of 1.8 mm with a distance between them = 15 mm and with a perimeter of slightly less than 3 m). The wave impedance of the square is about 110 ohms, so it is powered by a PRPPM cable - 2 x 1.2 (wave impedance is about 135 ohms). The height of the mast on the five-story building is approximately 9 m. The plane of the square is perpendicular to the line Chisinau - Bendery - Tiraspol - Odessa. As a result, more than 10 stations from Chisinau and 3-4 powerful stations from Odessa are heard.

Sources

1. A brief guide to the REA designer (edited by R.G. Varlamov). -M.: Sov. Radio, 1972, pp. 275,286.
2. V.T. Polyakov "Direct Conversion Transceivers". - M.: 1984, p.99.
3. P.M. Tereshchuk and others. Handbook of a radio amateur, part 1. Kyiv: Technique, 1971, S.Z0.
4. "VEF-221", "VEF-222". Manual.
5. Radiotechnika (T-101-stereo tuner). Manual.
6. A.N. Maltese, A.G. Podolsky. Broadcast reception in a car.- M.: Radio and communication, 1982, p.72.
7. V. Kolesnikov "Antenna for FM reception". - Radiomir, 2001, N11, p.9.

This article describes a simple and economical receiver that allows you to receive broadband and narrowband FM stations in the range of 30 ... 130 MHz. This receiver is useful for those who repair and assemble radiotelephones. An article was published on a simple radiotelephone operating in the 65 ... 108 MHz range. The choice of this range is due to the ease of setting up the radiotelephone using factory receivers. But if you wish, you can configure this radiotelephone outside this range, since the TDA7021 chip retains its performance in the frequency range of 30 ... 130 MHz, and the proposed VHF receiver will help with this. The circuit is distinguished by high sensitivity, simplicity and good characteristics, does not contain scarce parts, is easy to manufacture and adjust.

The principle of operation and configuration of the VHF receiver

The basis of the receiver (Fig. 1) is the DA1TDA7021 microcircuit, which is a superheterodyne with one frequency conversion and a low intermediate frequency (IF). This microcircuit contains a UHF, a mixer, a local oscillator, an IF, a limiting amplifier, an FM detector, a BSHN system and a buffer amplifier 34.

The signal from the antenna, as

Specifications

Received frequency range, MHz………………………….. 30…130

1 subband, MHz……………………………………………….. 30…50

2 subband, MHz……………………………………………….. 50…70

3 subband, MHz……………………………………………… 70…90

4 subband, MHz…………………………………………… 90…110

5 subband, MHz……………………………………………. 110…130

6 subband, MHz……………………………………………. 130…150

7 subband, MHz……………………………………………. 150…170

Sensitivity, µV……………………………………………………. 1

Current consumption, mA…………………………………………………… 12

Supply voltage, V………………………………………………. 3…6

Output power, W………………………………………………… 0.1

Load resistance, Ohm……………………………………. 16…64

the swarm serves as a wire from the headphones, goes through the capacitor C12 to an external UHF, made on the transistor VT1 KT368. The amplified high-frequency signal and the local oscillator signal, the frequency-setting circuit of which are inductors L1 ... L5 and capacitor C2, are fed to the internal mixer of the microcircuit. The IF signal (about 70 kHz) from the mixer output is selected by band-pass filters, the correction elements of which are capacitors C4, C5, and is fed to the input of the limiting amplifier. The amplified and clipped IF signal is fed to an FM detector. The demodulated signal, having passed through the low-frequency correction filter, the external element of which is the capacitor C1, is fed to the noiseless tuning device (SNR). Connecting the resistor R1 helps to increase the sensitivity of the receiver by turning off the BSHN device. From the output of the disconnected BSHN device, a low-frequency signal is fed to the buffer amplifier. Connecting the blocking capacitor C7 helps to increase the output voltage of the bass and more stable operation of the buffer amplifier. The low-frequency signal from the output of the buffer amplifier is fed through the capacitor C6 and the volume control R2 to the input of the low-frequency power amplifier on the DA2 TDA7050 chip. Inductors L6, L7 are used to decouple high-frequency and low-frequency signals when using headphones.

The receiver is tuned to the radio station by changing the resonant frequency of the local oscillator circuit. Range switching is carried out by the SA1 switch, which connects one of the five inductors to the local oscillator of the DA1 TDA7021 chip. Tuning in each range is performed by a variable capacitor C2. Inductors L1 ... L5 determine the setting of the required overlap of the respective range. The desired volume of the receiver is selected by a variable resistor R2. This completes the receiver setup.

The TDA7021 chip can be replaced with its domestic counterpart K174XA34. But it should be noted that not all domestic analogues can operate in an extended range. Instead of the TDA7050 chip, any low-voltage operational amplifier is suitable, but with an appropriate switching circuit. The KT368 transistor can be replaced with any low-noise RF transistor with a cutoff frequency of at least 600 MHz. The maximum capacitance of the variable capacitor C2 should not exceed 25 pF. With a large capacitance, an additional "stretching" capacitor should be connected in series with this capacitor, reducing the total capacitance to the specified limits. Inductors L6, L7 are used with any inductance of 20 μH.

The performance of the TDA7021 chip is not limited to the range of 30 ... 130 MHz. Experiments with this microcircuit have shown that it can work stably in the frequency range of 30 ... 170 MHz. This opens up even more possibilities for the receiver. Obtaining such a wide range is possible due to a good local oscillator excitation margin on the TDA7021 chip.

The table (see below) shows the coil data for the range of 30 ... 170 MHz. The entire range is divided into seven sub-ranges. Five sub-ranges are left the same, only two are added. Since the coils L* and L** are not

Coil data for 30…170 MHz range

The number of turns of the coils is indicated approximately, since their inductance depends on many factors, so the selection of turns cannot be avoided. The trimmer for contours can be used brass or ferrite. If desired, you can turn on the noiseless tuning system (BSHN) by replacing the 10 kΩ resistor R1 with a 0.1 μF capacitor, but the sensitivity of the receiver will deteriorate by about one and a half times. In stationary conditions, it is better to use a telescopic antenna up to 1 meter long instead of the headphone wire, while the L6 and L7 chokes must be excluded.

The modified receiver allows you to receive signals from home radio telephones, VHF FM broadcast radio stations, aviation services, amateur radio stations, extended-range radio telephones such as "SONY", "NOKIA", etc. Thus, the receiver has a wide range of capabilities that can satisfy most radio amateurs, operating in the VHF band.

Literature

1. Shumilov A. Simple radiotelephone // Radio amateur. 2001. No. 7. Technology for the manufacture of parabolic antennas for Satellite TV

Having become interested in receiving STV, radio amateurs, as a rule, acquire a ready-made set of equipment for this. It usually includes a parabolic antenna (PA) of small diameter (0.9 ... 1.2 m). One of the first steps in upgrading the system is…….

FET AM DEMODULATOR Fig.12.1 FET demodulator, assembled according to the above scheme, operates at a frequency of at least 100 MHz. Demodulation in this scheme is not carried out in the same way…….

LOW-PASS FILTER FOR ANTENNA M. Steyer, Funkamateur, Berlin, no. 7/97, ​​p. 820-823 The device uses a dual operational amplifier with a bandwidth of 160 MHz. Divider 143/60.4 Ohm reduces…….

PHASE/FREQUENCY COMPARATOR WITH THREE TRIGGERS L'Electronique par le Schema, Dunod, vol. 3, p. 177 Fig. 8.1 This device uses the first trigger (A) of one of the four-stage dividers of the CD4520…… chip.

Rare people think when they hear an announcement about FM radio, which means the phrase. According to accepted agreements, the term FM means broadcasting on a carrier frequency that fits in the segment from 87.5 to 108 MHz, with FM modulation. But this does not exhaust the variety of methods for transmitting entertainment programs. Extended range digital radios are designed to fill the gap.

More often than not, we are talking about increased VHF boundaries. Most products receive at frequencies from 64 to 108 MHz, selected models, for example, Mason R411, reach out to 233 MHz. Such a broad framework covers the broadcasting of entertainment radio stations, fully covering the standard values ​​​​accepted in aviation for negotiations.

We mention that within the Commonwealth countries the described equipment capabilities are hardly useful - transmissions are not carried out above 137 MHz - but on the territory of other states the option will come in handy.

Origin of the terms FM and AM

Every country has its own broadcasting standards. FM is considered to be the accepted name for the VHF-2 and VHF-3 bands in Western countries. AM refers to long waves (LW), SW1-SW11 accounts for all short-wave bands (HF).

The term FM comes from the English designation for a type of modulation called frequency modulation. The information is included in the deviation - the frequency deviation from the carrier value. In contrast, AM implies a change in another parameter of the electromagnetic wave - the amplitude.

Summarizing, let's say that in the upper region of the VHF range, FM (FM) modulation is used, and in HF, MW and LW - AM. This is the origin of their English-language names. To distinguish SW and DV from SW, the latter are referred to as SW.

It remains to add that SW is divided into 11 sub-bands, below FM there is an area designated OIRT (VHF and VHF-1), named after the modulation method - polar.

The main principles of expanding the received range

All wave digital radio works with most broadcast stations. This quality is ensured by a number of special measures.

To what has already been said, we add that the design of the antenna depends on the frequency of the received wave. For HF (3-30 MHz), the use of ferrite rod varieties is optimal, for VHF, a telescopic design is more appropriate.

Portable radios

The receiver preselector is tuned to the carrier by changing the value of the capacitance, less often the inductance, of the input filter. Naturally, it is not possible to cover the entire spectrum with a single resonant circuit; the range switching knob is useful to solve the difficulty. It flips the antenna input signal between loops with a variety of coverage areas.

To better understand what has been described, let's make an idea of ​​a band-pass filter. There are two main characteristics:

1. resonant frequency.
2. bandwidth.

The action of the filter is like a gate through which only the necessary part of the signal can pass, and the gate is able to move in different directions, passing to the exit of the station in turn. The knob of smooth adjustment and movement is regulated.

For a long time there has been a struggle to reduce the size and cost of equipment, but how to expand the range of a radio receiver without sacrifice is still unclear. The technology of transferring the received signal between filters is considered generally accepted.

The bandwidth of such a filter is equal to the width of the spectrum of the useful signal emitted by the radio station, and the resonant frequency - the center of the gate - is tuned to the carrier. If these conditions are strictly observed, the reception quality is the best.

Continuing the analogy, let's say that the AM and FM stations are located too "far" from each other, so the device that regulates the position of the gate does not "reach" there. The resonant circuits of an electrical circuit operate in a similar way. Switching ranges allows another circuit to “reach out” to a station that the current one lacks.

At the same time, the type of receiving antenna is changed. In this way, extended functionality is achieved.

The matter is not limited to combined antennas and refinement of input filters - each range uses its own type of signal modulation. The electrical circuit that separates sound from wave vibrations is different for a particular case.

Modulation is a change in the carrier parameter according to the law that describes the transmitted message. On the receiving side, the reverse action occurs - detection. The most commonly used modulation types for broadcasting are:

• amplitude;
• frequency.

In the first case, the carrier amplitude is subject to change, and in the second case, the frequency. Features of the propagation of waves in the air and the functioning of electronic components for reasons of effectiveness force the use of known types of modulation.

The whole variety of technical solutions is not limited to the described options, the terms single-sideband and polar modulation are separated. The need for sophisticated methods arises when it is necessary to transmit stereo sound over a channel of normal width, to save transmitter energy, and reduce the level of factors harmful to human health.

A digital radio receiver with a VHF range for working with HF must provide for switching the type of detector from frequency (FM) to amplitude (AM).

Technically, this is not difficult. To receive all radio stations, it is necessary:

• Have a number of antennas and input filters for different frequencies.
• Include detectors for different types of modulation in the circuit.
• Switch between specified items appropriately.

Radio receiving equipment Grundik

The use of several antennas and the refinement of the electronic filling described above make it possible to receive extended range waves. Here is how this principle is implemented by Grundig digital radio receivers (Satellit 750) for professional use:

• digital tuner covers all possible ranges of broadcasting and negotiations on authorized frequencies;
• 100 preset channels provide instant selection of the desired station;
• impact-resistant case, borrowed from measuring instruments, with protective handles reliably protects the device from damage;
• the ability to work with a pilot signal and single-sideband modulation is implemented for professional use;
• digital signal processors provide maximum sensitivity with minimum distortion;
• remote antenna with the ability to turn 360 degrees is installed in the place of the best reception;
• an additional increase in sensitivity is achieved by lowering the resistance on the gold-plated connector of the external antenna.

A more modest digital G6 Aviator pocket radio receiver differs from the described model in its small size, lack of a shockproof housing and remote antenna, and lower sensitivity. However, the device is located in the upper segment of household compact products. In order not to accidentally press an extra key, there is a HOLD lock button.

Grundig digital radios are equipped with numeric keys for dialing the frequency from the keyboard, line outputs for speakers and headphones, as well as several antennas for reliable reception in all ranges. All products are aimed at high-quality radio reception and are not entertainment equipment.

Applicability of extended range devices

From the foregoing, it is clear that extended range digital radios are of limited use. The explanation is simple: most popular stations are located in the FM band.

However, long waves at long distances are caught better, especially in bad weather, there is a demand for all-wave digital radios. Tourists, residents of remote villages, workers of facilities under construction - these people are interested in the operation of stations in the HF and lower frequencies.