We listen to radio amateur conversations on the computer and on the phone. Broadband RTL-SDR receiver. We listen to radio amateur conversations on the computer and on the phone Conditions for the operation of this scheme
As you know, I am interested in the subject of walkie-talkies, and sometimes I even review some of my devices.
So today I decided to tell you about a rather interesting thing. RTL-SDR signal receiver based on R820T 8232.
I will also tell you how to set up this receiver to work on a computer and on an android phone / tablet.
So, there are already several reviews about SDR receivers. Therefore, I will not describe in detail what it is.
I will only say that you can buy a cheaper version of the receiver and finish it with a soldering iron.
Like this: 
You can buy a kit. Like this: 
()
And to assemble the receiver, having spent several evenings on it, at the same time pumping the skill of the solder.
Or do it like me: buy a product that is ready to receive all the necessary products, which can be used without dancing with a tambourine. The difference in price is not very big, so I bought a ready-made receiver, with an additional board, all the necessary jumpers in the right places, and even two outputs for antennas.
This particular receiver can receive signals and cover all the HF amateur bands:
covers VHF and UHF 24-1766 MHz
up to 3.2 M Sampling rate (~ 2.8 MHz stable)
receiver modes, MFM, FM, USB, LSB and CW PRODUCTION
What does it mean? This means that we can listen to programs on the following ranges:
13-15MHz These are distant broadcasters like the voice of America.
15-28MHz you can hear amateur radio communications.
27.135MHz this is a truckers' channel (it is convenient to listen to on long trips).
30-50MHz there may be an ambulance.
87.5-108MHz this is an ordinary FM radio.
109-500MHz The most interesting)
108-136MHz this is the air range (pilots talk here, not without jokes and gags)
137-138MHzthis is the range of NOAA satellites (satellite weather in low resolution)
144MHz again radio amateurs
150MHzthis is the railway range.
433MHzalso radio amateurs, talkie-talkies, key fobs for signaling, barriers and other ethereal debris
446MHz talkers too
then it already depends on the city, by the way, the police are also somewhere here) but I won't say where)
~ 900MHz cellular.
More information can be found on the website
Now directly about the receiver.
The receiver was ordered for banggood. (there he was in stock at the time of purchase. And the price was good.) I ordered 2 receivers: 
Delivery took 30 days. At the post office I received a parcel with two boxes. One box with the receiver remains until better times (I'll put it in the car later) and the first is used for testing and tuning.
The receiver comes in a regular box. Which also suffered a little: 
Inside there is a receiver, antenna, mini-usb cable: 
In fact, nothing else is needed.
Details.
Cable:
The cable is the most common mini-usb. By the way, I didn't even bother using it. Since I have my own, longer and higher quality.
Antenna:
Has a magnetic pad. The magnet is pretty strong. Adheres well to vertical metal surfaces. 
Himself receiver:
Unremarkable box. 
Has dimensions 90 * 50 * 22mm: 
On the one hand, there are connectors for connecting two antennas: 
On the other hand, a mini-usb connector for connecting to a computer and a power indication LED: 
If you don't know for sure, you don't even understand what kind of device it is. Moreover, there are no identifying inscriptions on the box. ( and they are not needed)
A couple of pictures in the interior, along with the wouxun radio: 
The kit comes with only 1 antenna, despite the presence of two connectors for different frequencies.
To operate at frequencies of 100khz-30MHz, you need to buy a second antenna. Provided that you want to listen to something in this range.
Before using it, I decided to disassemble the receiver. The reason is simple. Inside, something dangled strangely. (bumpiness is present on both copies of the receivers I purchased) 
The whole parsing process consists of unscrewing 4 screws: 
Even in the photo you can see that everything is neatly unsoldered. There are no traces of flux or other crime.
It can be seen that this is a DVB receiver wired to the board. The main chips of R820T and 8232: 
I can't tell you anything more. Since he is not strong in circuitry. You can see everything in the photo.
Now about what was thundering inside. This is the board itself. It is slightly smaller than the body slots and slightly shorter. That's why it dangled inside. I solved this question simply. I glued the foamed 2-sided tape inside the case, and put the board in place: 
Everything spun tightly. Backlash and chattering are gone.
Now I'll tell you about setup and testing:
To work with the receiver on a Windows computer, we need to use the program sdrsharp
To install the correct drivers, you need to run the zadig.exe program
If you do not have it in the assembly with the sharp,
Run, select options - list all devices
Select the item Builk-In, Interface (interface 0) and click the Reinstall Driver button: 
After that, the necessary drivers will be installed in the system, and you can run the SDRSharp program.
Everything is simple here. In the settings, select the desired port, and press the start button: 
Frequencies can be entered either manually or using various plugins for scanning.
(working with the program will draw you to a separate article, there are so many possibilities in it. Therefore, I show it superficially, and those interested can already find details on the Internet)
What is such a receiver for?
Despite the comments about all sorts of atrocities, and about what to promote, this receiver is actually quite legal. And you can use it for legal purposes. And besides, it is NOT FORBIDDEN to listen to the broadcast. And it is impossible to transmit something on the air using this receiver. Therefore, with the help of the receiver, we can listen to the radio. Yes, regular radio. Suddenly you do not have a single device that can receive signals from local radio stations, and the radio will help you listen to horror as you want.
Even with the help of the receiver, you can listen to radio amateurs broadcasting at frequencies of 15-28 MHz
But a more powerful antenna is needed. The one that comes in the kit will allow you to receive a signal only when you are near the source of this very signal.
You can also check the radio with the help of the receiver. Classic situation: they brought an old walkie-talkie without a display. Working, but it is not known at what frequency. You can use this receiver for detection. (of course there are separate instruments for measuring frequency and power, but if there is a receiver, you can do with it)
Well, for example, we went on a long journey. On your own by car. Why don't we tune the receiver to the frequency of CB truckers ( 27.135 MHz) to listen to the talks? To know what's going on on the road? Where is the ambush of the traffic police, where are the accidents, where is the detour, etc.
By the way, it is not necessary to connect the receiver to a laptop to listen to the CW band. Android phone can be used. And not only for this range.
I connected the receiver to my Xiaomi Mi5 via a penny OTG adapter. Setting up here is even easier than on a computer:
Go to w3bsit3-dns.com and download the program
Together with the program, download the Rtl-sdr driver 3.06 and the key to get full functionality. ( you can, of course, buy a key on the market, but I'm an old pirate who loathes paying for software)
Install on the phone: 
Screenshots from the application: 
As you can see, everything works great, and also allows you to listen to the broadcast. 
I tested this receiver with my Baofeng, Wouxun, WLN radios. Everything is perfectly caught.
Also, with the help of a scanner, I was able to find several frequencies on which there were conversations. Which confirms the efficiency of the receiver.
I have a receiver mainly for a hobby, but there is an interest in listening to shortwave from other countries, so now I am choosing an antenna for this receiver (I will be grateful if you suggest your options in the comments)
Conclusion:
This receiver is a great option for people interested in radio. It allows you to learn a lot, as well as listen to the air without buying expensive equipment.
I cannot dissuade or recommend this product for purchase. Too specific product. I am personally very pleased with the purchase. And this is the most important thing.
Next month I have a long trip planned by car, and I am looking forward to it not so much for the purpose of the trip, as for the opportunity to listen to negotiations and test the receiver in the field.
A schematic diagram of a scanning device for a VHF-FM receiver is shown in Fig. 1. The clock generator is made on the elements D1.1 D1.2, its frequency is 7000Hz. This frequency provides coverage of the entire range in 2.5 s. The generator is controlled by an RS flip-flop on D1.3 D1.4.
When power is applied, the R4C3 circuit sets the D2 counter to zero. A low level on pin 2 of D1.1 enables the operation of the clock generator and the state of the counter begins to change. Matrix R5-R26 is used to convert the binary code into voltage. The resulting voltage is removed from C3 and through R27 is fed to the receiver varicaps.
The voltage of the fine tuning from the receiver is fed to the input of the comparator made on the OA A1. The reference voltage from the R3 slider is applied to the inverting input. Until the receiver is tuned to a station, the fine tuning voltage is low, and zero is present at the A1 output. When tuning to a station, the voltage at the non-weighting input of the comparator increases, and when it exceeds the reference voltage, the comparator will switch to a single state. A short pulse formed by the C6R28 circuit will switch the RS-flip-flop on D1.3D1.4 to the state 1. This unit prohibits further operation of the generator and counter D2. this will tune the receiver to a station.
Pressing SB1 will start the counter again, for further tuning to another station. To return to the beginning of the range, use the SB2 button.
To indicate the location of the station in the range, the diagram shown in Fig. 2 is used.
Figure 3 shows the connection diagram to the K174XA42 microcircuit, which does not have a fine-tuning output, but it is not difficult to obtain it by adding several elements to the receiver circuit on the K174XA42.
This scanning device circuit is intended for receiver circuits with a directly proportional level of received signals, but if the microcircuit has an inverse law of fine tuning voltage formation, it is enough to swap the A1 comparator inputs.
Establishing the device is reduced to setting the reference voltage (R3). If there is no need for a forced return to the beginning of the range, then the SB2 button can be removed, you get a fairly convenient scanner with a circular control for searching for radio stations.
Literature RK2001-6
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VHF (FM) receiver is an integral part of a sound reproducing complex of any complexity. Modern circuitry solutions and element base allow achieving high reception characteristics. Therefore, the radio amateur, taking one of the typical schemes as a basis, can focus on improving the service characteristics of the device under construction. This primarily applies to the controls.
In recent years, there has been a clear trend towards abandoning mechanical scales and adjusting organs controlled by complex vernier devices. In amateur radio practice, this is also due to the fact that making a good and beautiful scale and vernier device in artisanal conditions is problematic.
Most modern receivers are tuned using varicaps, this makes it possible to tune using digital voltage synthesizers with quasi-analog scales, where the slider is simulated by a luminous LED or indicator segment.
And the setting is done by pressing the "+" and "-" buttons. Many similar devices of varying complexity have been published in the amateur radio literature, but most of them have a significant drawback:
the button has to be held all the time of setting. The tuning speed with manual control is low, and to adjust over the entire range, you have to hold the button for 15-20 seconds.
However, there are other ways to build such devices. Almost all modern microcircuits for FM receivers, except for K174UR3, have a fine-tuning voltage output for connecting an indicator. This output can be used to automate the setup process so that one short press on the button is enough.
As practice shows, in most cases it is enough to rebuild the receiver in one direction with the possibility of returning to the beginning of the range with the "reset" button. A similar method is used in portable receivers of foreign production, built on the TDA7088 or its analogues. In this case, the tuning rate can be quite high and the tuning of a receiver equipped with such a device practically does not differ from enumerating fixed settings in a ring.
A schematic diagram of such a tuning unit (scanner) is shown in Figure 1. The clock generator is made on the elements D1.1 and D1.2, its frequency is chosen about 7 kHz. At this frequency, it takes about 2.5 seconds to cover the entire range. The generator is controlled using an RS-flip-flop on the elements D1.3 and D1.4.
When the supply voltage is applied, the R4 C3 circuit forms a short reset pulse, which sets the D2 counter to zero. The same pulse, through the diode VD1 and the capacitor C2, sets the RS-flip-flop D1.3-D1.4 to the zero state. A low level at pin 2 of D1.1 enables the operation of the clock generator and the state of the counter D2 begins to change. To convert the binary code into voltage, an ADC based on the R-2R matrix R5-R26 is used. The advantage of this solution is that only two resistors are used in the matrix, which greatly simplifies the selection of the element base.
The thus obtained tuning voltage is removed from the capacitor C5 and fed through the resistor R27 to the receiver varicaps.
In the process of monitoring the radio broadcast, the main actions are the search, detection and reception of the required radio signals. The capabilities of any radio monitoring complex that solves these problems are determined by the parameters of the scanning radio receivers used in it. In essence, these devices are one of the most important functional elements of such a complex. It should be noted that scanning receivers in the hands of intruders can serve as a reconnaissance tool.
Scanning radios are characterized by the following main indicators:
range of received frequencies, sensitivity;
selectivity;
scanning parameters (tuning speed, stripes
review, etc.);
the signal detection method used;
the type of received radio signals;
efficiency of management and the possibilities of its automation;
output parameters (quality of signal playback
at the output of the receiver, the presence of outputs at the intermediate and low frequency, the values \u200b\u200bof the signal passbands at these frequencies, etc.);
operational parameters (weight and dimensions, power requirements, reliability, maintainability, ease of transportation, etc.).
In terms of weight and dimensions and functionality, scanning receivers can be conditionally divided into portable and transportable. Portable devices include small-sized devices weighing more than 350 g, with autonomous power sources. These devices in the frequency range 100 (500) Hz ... 1300 (1900) MHz receive signals with amplitude (AM), narrowband (NFM) or wideband (YWFM) frequency modulation. Some samples record single-sideband AM (SSB) signals transmitted on the upper sideband (LSB) or lower sideband (LSB) frequencies, as well as radiotelegraph (CW) bursts. When receiving with a signal-to-noise ratio of 10 dB / μV, the sensitivity of the scanners is 0.35 ... 1 μV for NFM and 1 ... 6 μV for WFM. With a tuning step from 50 ... 500 Hz to 50 ... 1000 kHz, the scanning speed reaches 20 ... 30 channels per second.
Information about the signal frequency is recorded in memory devices with a capacity of 100 to 1000 independent channels. Individual devices are controlled by a PC.
The appearance of typical portable scanning receivers is shown in Figure 12.1.
Figure 12.1 - Portable small-sized scanning radios:
a) IC-R3 (frequency range 0.495 - 2450.095 MHz; dimensions 61 * 120 * 33 mm; weight 300g.
b) IC-R5 (frequency range 0.495 - 1309.995 MHz; dimensions 58 * 86 * 27 mm; weight 170 g).
Transportable receivers, differing in size and weight reaching 8 ... 20 kg, have much greater capabilities, almost all samples are controlled by a PC.
The appearance of typical transported scanning receivers is shown on
figure 12.2.
The widespread introduction of computer technology has led to the emergence of a new generation of scanners.
Figure 12.2 - Transportable scanning receiver
Scanning receiverWinradiomade in the form of a card (printed circuit board) installed in a 16-bit slot of an IBM-compatible computer, due to which the speed of scanning, panoramic view and measurement of signal levels exceed those of scanners connected to a PC via a serial port.
SuperheterodyneWR-1000 range 500 kHz ... 1300 MHz with triple frequency conversion can receive signals in AM, SSB (CW), NFM and WFM modulation. The program (versions for and WINDOWS) allows you to quickly manage the resources of the device. Data input and mode selection are carried out with the keyboard or mouse. The control panel is displayed on the monitor screen. The frequency step is adjustable from 1 kHz to 1 MHz, the scanning speed is 50 channels. The number of memory channels is determined by the capacity of the hard disk. The device implements all modes inherent in scanning receivers, allows you to display a panorama of the loading range in the coordinates "Level - Frequency" (AFC), to analyze the group spectrum of signals and noise or individual signals. The signal is tuned to you when you press the mouse button once. More advanced model WR-3000i - DSP supports WINDOWS audio standard. Recently released external (all-in-one) models WR-1000e, WR-1500e and WR-3100e are equipped with PPS batteries and a PCMCIA interface card with a cable for connecting to a laptop.
There are three main operating modes for scanners:
automatic scanning in the frequency range;
automatic scanning at fixed frequencies;
manual scanning.
When implementing the first mode, the boundaries of the scanning range, the frequency tuning step and the type of modulation are set. To reduce the time, it is possible to scan with skipping frequencies, the data about which are stored in the memory of the machine. Typically, modern scanners have 4 to 20 programmable frequency ranges.
There are several scanning algorithms:
scanning is interrupted if the level of the received signal exceeds the specified threshold, and resumes at the command of the integrator;
scanning is interrupted when a signal is detected and resumes after its disappearance;
scanning is interrupted when an audio signal appears and continues after it disappears;
the scan is interrupted for the operator to analyze the signal and continues after a while.
A number of scanners record signal frequencies during scanning, in particular, in the AR-8000 50 channels are allocated for these purposes.
The second mode of operation is used to organize control over radio equipment with known frequencies. At the same time, some samples provide scanning for a given type of modulation, as well as for priority channels.
In manual scanning, the receiver is rebuilt by the operator, and the information is displayed on the liquid crystal display. In a number of samples, the display shows the relative signal strength in the form of an n-segment diagram.
There are a number of practical considerations when purchasing a scanning receiver.
Excessive number of channels will cause a proportional increase in programming and search time for the desired source. The actual number of channels required does not exceed 400. At the same time, it is desirable that the channels be divided into banks, which will make them more accessible for search and simplify the task of assigning them to special groups of sources.
Many scanners have dips in the frequency range. It is possible that unknown sources operate precisely in areas inaccessible for reception with such a device. The wider and more continuous the operating frequency range of the scanner, the more effective its application.
The increase in scanning speed is achieved by introducing the most complex schemes, which dramatically increases the cost of the device. It is advisable to use devices whose scanning speed does not exceed 50 channels per second. It will be very beneficial to purchase a scanner capable of holding the received frequency for a few seconds required for preliminary analysis. Then, in the event of a short break, for example, during full-duplex transmission, the scanner will not go further along the range in search of another operating frequency.
Considering the overload of the radio spectrum and the fact that the conditions force transmitters to work in the near-field zone of radiation, one should not strive for possessing a supersensitive device, so this does not promise anything but unnecessary noise in the path. The sensitivity of the scanner is selected based on the intended application.
The existence of many types of signal modulation makes it necessary to opt for a device that detects a signal with the greatest number of modulating influences.
The ability of the device to register the signal power level can be very useful, which will allow for the selection of sources by distance from the receiving point.
The presence of the priority channel selection mode allows you to automatically switch to the analysis of the most important source in the course of an ordinary scan.
If the scanner is going to operate in conditions of strong acoustic noise, you should pay attention to the output power of the device, which should not be less than 200mW.
Considering the versatility of the scanning receiver as a detection tool, it is necessary to purchase a device whose power supply system will allow it to be operated in stationary and field conditions. High-speed receivers have versatile detection capabilities. They are able to automatically, within a fraction of a second, scan the range from a few to several thousand megahertz, fix the frequency of the signal, the level of which exceeds the intensity of the radiophone by 15 ... 20 dB, and provide real-time listening to information transmitted over radio channels from AM and FM.
Text reception "Releven"carries out reception and detection of signals with frequency modulation (deviation up to 100 kHz) in the range from 30 to 2000 MHz. The frequency converter unit allows you to view the entire range in less than 1 second. The sensitivity of the device is much higher, for field indicators, and is 100 μV at a frequency of 500 MHz. The receiver memory unit can store up to 1000 values \u200b\u200bof frequencies of signals of radio broadcasting and television stations, which will be excluded from consideration during subsequent scanning.
In "R11" there is no frequency counter, but the LED indicator allows you to set the belonging of the received signal to one of ten sub-bands 30 ... 88, 88 ... 108, 108 ... 144, 144 ... 174, 174 ... 420, 420 ... 470, 470 ... 800, 800 ... 920, 920 ... 1300, 1300 ... 2000 MHz, and through the CI-V serial port the device can be connected to the SCOUT frequency counter. Built-in Ni-Cd rechargeable batteries (7.2 V, 600 mA) provide continuous operation for 5 hours. Dimensions of the metal case 108 x 63 x 32 mm.
ReceiverXPLORERpossesses wider functional capabilities, allowing to perform manual and automatic capture of radio signals in the range of 30 ... 2000 MHz, to detect them and provide listening through the speaker. In addition to blocking unnecessary signals of broadcasting stations when scanning up to 1000, it is possible to write to a special memory block about 13 parameters about 500 received signals, including: frequency, number of repeated appearances on air, time and date of activation, level, deviation, type of modulation, etc. etc.
Through the serial interface RS-232C the receiver can be connected to an IBM-compatible computer to read information from the memory registers in text mode.
The charger recovers Ni-Cd batteries (8.6 V, 900 mAh) in 1 ... 1.5 hours. The display shows: frequency value with 100 Hz accuracy, relative signal level, modulation type. Dimensions of the metal case 140 x 70 x 40 mm, receiver weight 250 g.
DeviceMRA-3 range 42 ... 2700 MHz receives signals with AM, NFM and WFM modulation, indicates their relative level, displayed on a linear LED display. The sensitivity of the RF channel of the receiver is from 20 to 60 μV in the range of 50 ... 1200 MHz and from 60 to 100 μV in the sub-bands 42 ... 50 and 1200 .. 2700 MHz. IF bandwidth - 400 kHz. Scanning of the working range occurs within 6 s with simultaneous recording of signals into the memory, which includes 512 long-term and 16 operational channels, protected from unauthorized access.
For the initial recording of the radio spectrum, the receiver scans the range 4 times in a row, and then switches to automatic mode. On each "pass" new and recorded signals are compared. When an unknown source is identified, an alarm is triggered, and information about it is entered into memory for analysis. The weight of the device is 620 g with dimensions 136x49x137 mm.
Portable device "Scorpion"in automatic mode, it allows you to view the range of 30 ... 2000 MHz in 15 seconds and, having detected an illegal transmitter with a narrow-band or wide-band FM, listen to the signal or suppress its reception channel by placing an aiming noise interference at the set frequency, created by the built-in noise generator and modulator. The control micro-computer makes it possible to memorize the values \u200b\u200bof 524 frequencies, 128 of which can then be excluded when re-analyzing the radio environment. With a passband at an intermediate frequency of 200 kHz, the sensitivity of the receiver in the 30 ... 1000 MHz sub-band does not exceed 50 μV, and in the 1000 ... 2000 MHz sub-band - 1000 μV. The liquid crystal 16-bit indicator displays information about the frequency and level of the input signal. Case dimensions (without antennas) - 165 x 90 x 29 mm.
Product "Python"is capable of scanning the 30 ... 1000 MHz range in 2 seconds and, having detected an FM signal, the level of which exceeds the specified one, instantly tune in to it, ensuring listening. Having a level indicator and an acoustic linkage mode, the device can be used to search for the installation sites of radio microphones. Dimensions 146 x 70 x 45 mm.