Hi-Fi stereo FM tuner with digital scale and electronic volume, tone and balance control. VHF receiver (FM tuner) with analog tuning Homemade fm tuner

Homemade FM tuner

When I want to listen to music, I take an audio CD and put it in the CD drive. The CD has high quality recording and as much as 80 minutes of music.

Surprised me too. These audio CDs are old. Here on my hard drive I have several gigs of MP3s with high bitrates from almost all the artists I like. Only a rare song is not found in my collection. And playback can be adjusted through the equalizer to suit your hearing aid;).

No, well, you guys are completely behind the times. Keep running around with your blanks and hard drives. And I have an FM tuner. I want to, I listen to one station, and if I’m tired of it, I listen to another. Always up to date thanks to the news. And I’m just keeping quiet about cool radio programs and pranks; listening to them can have a tremendous amount of fun and lift your spirits. In addition, sound can be recorded from the tuner and converted into any convenient format such as MP3, OGG, etc.

Interesting dialogue, isn't it?

If your hands are not crooked

Yes, that's for sure, skillful hands will be needed here. Today, buying an FM tuner is not a big problem. But if a person wants to test himself as an avid electronics engineer, as our fathers and grandfathers did in the 60s and 70s, then this will not require so many financial and human resources.

Well, really, what’s so difficult about assembling your own receiver and controlling its settings from a computer?

Receiving device

In Fig. Figure 1 shows an electrical circuit diagram of an FM radio receiver assembled on a single K174XA34 chip (analogous to TDA7021) with a DIP16 housing, that is, with 16 legs. I note that a similar microcircuit can have 18 legs, but why do we need such a giant centipede? ;)

This microcircuit can operate on a power supply of 2.7...7 V, which means that 5 volts from the computer will be enough for it. And it consumes wow - nothing at all - 7-8 mA. Personally, I never managed to burn this chip, despite the incident with the power connection reverse polarity, but still, in my opinion, it is more convenient when the microcircuit is installed in the socket. Well, the man is weak. Yes, there is such a thing - I like sockets on DIP16 ;)

A little about the scheme: capacitors C1-C5 with a nominal value of 0.1 µF; C6 - 68 pF; C7 and C8 - 100 pF; C9 and C12 - you can use Philips electrolytics at 47 uF per volt 16; C10 - 1500 pF; C11 - 820 pF; C13 - 6800 pF; C14 - 300 pF; C15 - 300 nF. I recommend purchasing containers with pico- and nano-values ​​in the form of yellow, two-legged droplets. Looks aesthetically pleasing;)

Resistors MLT 0.125 W: R1 - 100 kOhm; R3 - 330 Ohm; R2 and R4 - tuning 0.125 W at 150 kOhm and 10 kOhm, respectively. Varicap VD1 brand KV109 with a red or white dot on the body.

In the local oscillator circuit circuit, capacitance C16 should be set to 7..10 pF (blue or brown droplet on two stilts;0)) to receive the range 88..108 MHz (FM or also upper VHF, that is, VHF2).

Inductance L1 can be wound with five turns of 3 mm diameter varnished single-core copper wire with a diameter of 0.5 mm with a pitch between turns of 1 mm. For convenience, as a core for mechanical fastening of the winding, you can take a 10..12 mm long fragment of a spent rod from a regular ballpoint pen.

Preparing to turn on and configure. Before turning on circuit R4, set the maximum signal transmission to point B, and from point B, send the signal to the linear input of a tape recorder or computer sound adapter. Although the signal is weak - only 50 mV, it should be quite audible. A voltage of 3.6 volts should be applied to point A, and R2 should be set to zero to transmit this voltage to the varicap VD1. When you turn on the receiver, you should listen to the radio broadcast of the TV channel “1+1”. If not, then by barely stretching or compressing winding L1 with a regular sewing needle and clinging to the outer turns, you should adjust the circuit to receive this station, which is at the beginning of the FM band. Then set R2 to transmit voltage 3.1..3.6 V to the varicap and make sure that the receiver receives a signal, for example, from the “Our Radio” radio station, which is at the end of the range.

Upon completion of the setup, I recommend that, unnoticed by your fashionista sister, take her favorite nail polish and fix the L1 turns on the core with 2-3 strokes of a brush, so that shakes and careless touches do not disturb her frequency characteristics.

Since this article is not so much about radio hardware engineering, but about how sophisticated a homemade FM tuner can be made, let’s move on to further development its capabilities.

Can't hear the neighbors ;)

“No, really, what’s the matter? Such a sophisticated receiver chip, but it produces only 50 mV of sound at the output. This is not the case, with the current speakers!” -

I can already hear the dissatisfied exclamations of readers, and even more, I can already see some of their veins beginning to swell with indignation. Whatever you say, I have a balm for their wounds. Yes, if everything was so simply solved, we would already live on the Moon;)

This audio amplifier (AUS) circuit is not new, but it can do something. Namely sound signal 25 mV, which we supply with resistor R4 of the previous circuit to point B, is amplified to 0.7..1.1 V at point D, which is quite suitable for supply to the linear input of a tape recorder or computer sound adapter. In this diagram: capacitances C1, C2 are electrolytic, 22 μF and 100 μF, respectively; MLT resistors R1 - 220 kOhm 0.125 W, and R2 - 200 Ohm 0.25 W. Transistor brand KT3102 (white dot on the cap, and green on the side).

With some skill, you can even connect a 0.5 W speaker with a resistance of 8 Ohms between point D and the common wire. But this is true.

Digital setup;)

Yes, of course, R2 allows you to tune the receiver to any wavelength and that might be enough for us. But where have you seen a commercial FM tuner with a knob for adjusting the reception frequency? This is an anachronism for the 21st century, not to mention the fact that during many days of operation, due to dust contamination, the tuning resistor, when adjusted, will begin to lead to interference and loss of reception, not to mention a very rough adjustment. Moreover, since we are worse than some Chinese who collect noname tuners? Yes, we can’t live without numbers now;)

So I say that it is difficult to find an alternative to a DAC assembled on an LPT port. And here, by the way, is it in Fig. 3

Oh, where is my youth, where is 1995, when instead of a SoundBlaster I didn’t even buy, but assembled a passive Covox on 16 MLT 0.125 W resistors, where some (green in the picture) had a nominal value of 15 kOhm, and others (red in the picture) 7.5 kOhm. The board then turned out to be so small that it easily fit into the Centronics plug housing. As I remember now, IT friends come and ask:

Heh, who bit off your printer? And where is Covox?

Yes, here it is, I tell them.

And how I ran the old Wolf3D on it...

Oops, I got carried away. Well, that’s not what we’re talking about, although...

Well, what can I add here? Actually, there’s nothing superfluous here, everything you need is with it, with a digital-to-analog converter (DAC), and in bourgeoisie DAC, “duck” means. They are there, so they specialize in “ducks” - hunters were found. Here we are hunting on the Pripyat River - you'll get pumped. Oh, something carried me away again. Readers will think that I celebrated something yesterday. ;)

So, by sending bytes with a value from 0 to 255 to the output via the LPT port, you can control the receiver settings and listen to whatever you want without looking for a regulator. But the point here is that this DAC circuit provides only 256 tuning steps, which ensures discreteness, that is, step, that is, tuning accuracy of everything (108 MHz - 88 MHz) / 256 = 20 MHz / 256 = 78 kHz. Well, yes, as much as 78. Although what kind of “as much” is there, when rather it is “just”, because the broadcast bandwidth of the radio station is about 100 kHz (frequency deviation 50 kHz), and it is likely that not all stations can be received with good quality, since the adjustment step is very large. It’s a strange thing, but back in 1997, when stations in the FM band were placed at intervals of 150 kHz, they were received quite well. But now there are more of them, and lo and behold, our tuner will simply skip some station.

Well, what are the problems? The LPT port also has 4 printer port control contacts, and if at least 2 contacts are placed at the top of our DAC, the resolution will improve 4 times, and will already be 20 kHz. Which isn't so bad.

What's there? Connect all 4 legs to the DAC through additional similar pairs of resistors and here you have a tuning accuracy of 5 kHz.

Someone will say that in order for the receiver to work with such a setting, you will need to create a program to control this device. So what? And who doesn’t program today in our progressive times? ;)

And I almost forgot, it is from the analog output of our, so be it, “duck” that the adjustment signal should be sent to point A (see Fig. 1).

I note that for normal operation as a DAC, the LPT port must be in SPP or EPP mode (see BIOS SETUP).

- "Where are you? Answer me!” or the saga about auto-search

It's time to talk about automatic frequency adjustment, which will allow the program to automatically find the next station on the range and not bother users, that is, your loved ones.

By simply amplifying and inverting the signal from pin 9 or point C (see Fig. 1) by monitoring the settings of the receiver microcircuit to the station, you can obtain a digital signal at point E in the form of a logical one if there is no station, and a logical zero if the station is caught. And all because on pin 9 of the receiver microcircuit a signal of about 0.7 V is generated in the first case, and in case of success the signal is less than 0.7 V. Which I did not fail to take advantage of.

In the circuit: C1 - 100 nF; MLT 0.125 W R1 - 6 kOhm, R2 - 0.25 W 100 Ohm; transistor KT3102; one logical element DD1.1 on K155LN1 (K555LN1, analogue of SN7404N/J).

I must say that the receiver chip has its own behavioral characteristics, and therefore this scheme does not always give the expected result, that is, for example, out of 16 radio stations, 12 are received reliably. Although not all Flash-FM-MP3 players can boast even such a result, we will still be looking for a better life. Moreover, all you need for this is;) look at the diagram in Fig. 5

where the source of the analyzed tuning signal will be the sound of the station itself (point D, see Fig. 2), and since tuning is always carried out at the peak of reception, we will catch it: the VD1 diode is an ordinary weak rectifier, you can use a high-frequency D9 brand or any other , suitable for its small size (no larger than a regular MLT 0.125 W resistor); C1 - 100 µF; R1 - MLT 0.25 W 100 Ohm. The logical inverter and transistor are the same. Then at point E we will already have a logical one in the case of a caught station, and a logical zero in case of failure.

And now, by sending a signal from point E to one of the five LPT inputs, you can monitor the receiver settings. Thus, until there is a signal of luck at point E (!), we should increase the setting value on the DAC until we reach the end of the range.

I note that power is supplied to the logical chip DD1 as follows: leg 14 (+5 V), and leg 7 (GND - to its ground ;)).

Whipping cream or a story about a real mixer

I heard somewhere that if you spin a cow very quickly in a centrifuge for some time, it will eventually produce cream. ;ABOUT)

Of course, by supplying sound from our tuner to the input of the computer sound adapter, we are unlikely to need an additional volume control circuit, since it is already implemented in the adapter. But! After all, the author really wants to show off;)

That's why you see fig. 6 ;)

and on it is precisely that a multiplexer is assembled on the K561kp1 chip (analogous to CD4052A), or, in simple human language, a two-channel 4x2 switch. Of course, we have one sound channel involved and therefore we take and use metal scissors to bite off only half of the chip, we don’t need to get too much, and put it together in a pile with 1 kOhm MLT 0.125 W resistors. The original switched signal can be taken from point B (see Fig. 1) or from point D (see Fig. 2). We apply signals to legs numbered 9 and 10 of the chip from any two LPT control outputs free from the DAC in order to control a two-bit address for switching the signal volume from an attenuator on three resistors (divider, in short; O)) to the output at point F. An address value of zero will give maximum volume, and a value of 3 (one at both address inputs) will give silence. Why is it so difficult? Yes, just so that no one guesses ;O)

If four volume levels are not enough for someone, they can take the K561kp2 (8x1) microcircuit and provide as many as eight volume levels. But this is already without me;O)

Diet food

The nutritional plan is a classic dietary one from AON or ZX Spectrum, if anyone remembers. ;)

Namely in Fig. 7

The supply voltage stabilization circuit is assembled on a K142EN5A chip (analogous to mA7805U). In this case, we take 12 V from the computer, and we get the 5 volts we need, clean, smooth and without interference. Conductors C1 are 100 µF, and C2 are 47 µF. Why should you use 12 V from your computer? That's how it should be! And that's all here ;)

Of course, for such a low-power monster like our tuner, such a chic stabilizer will be fat (it itself already consumes 10 mA), but this will also protect the computer from the “goat” ( short circuit power supply to the common wire) in the receiver circuit.

You can hear it, but it doesn't warm you up

As far as I know, for this K174XA34 chip there is a sparring chip K174XA35, which is a stereo decoder for a stereo radio broadcasting system with polar modulation for VHF radios. So the story with the improvement of the tuner does not end there and everything depends only on the imagination of the experimenter.

The wider the screen, the better;)

A shielded audio cable should be connected to outputs B, D or F, depending on the evolution of your tuner. It's better to buy one like the one for CD-ROM. Also, it would not hurt to put a ferrite tube with a diameter of 2.5 mm and a length of 5 mm on a power wire with 5 volts, or just take a ferrite ring and make 5-10 turns on it with the same wire between the capacitor C2 of the power circuit and the rest of the circuit. This whole bunch of silicon and copper wires should be placed in a metal box. The antenna can be taken from any imported TV that is included in the cable TV network. Yes, he doesn’t need her in this situation. It's just gathering dust in vain. ;)

Actually, readers don’t have to do all this. For just one attempt to read this article, readers (and the editor should not forget; O)) should erect a monument during his lifetime.

My house is on the edge

Well, what can I say finally? Personally, I used such a seemingly wild device back when I had a 386th machine. No, this is not a Mercedes model. This one is like... well, in general, why do you need it?

So everything caught, and I was happy. I’ll say right away that I didn’t learn to solder yesterday, but graduated from one of the capital’s universities, which is why I look so competent. ;)

And remember that if something burns in your computer after this, then I have nothing to do with it. What, did I scare you? Do not be afraid. Nothing will burn there, even if you try very hard.

Happy broadcast!

Hi- FistereophonicFM-tuner with digital scale and electronic control of volume, tone, balance.

http://www. acust. *****/files/statja6/statja6.htm

Specifications

Receiver sensitivity 2-3 µV

Received frequency range 85-111 MHz

The range of frequencies displayed by the indicator is 30-199.9 MHz

Frequency range Hz

Maximum distortion level 0.1%

Maximum output power per channel 3 W

Volume control depth -70….-2 db

Bass tone control depth -14….+13 db

HF tone control depth -11….+13 db

Supply voltage +12…..+25 V

Receiver dimensions (mm) 270x50x215

The receiver is made entirely of modern components, which made it possible to obtain good quality sound and excellent sensitivity. The receiver consists of 8 main components: power stabilizer, digital indicator, electronic part of the digital scale, electronic volume control, control and indication board for volume, balance and tone, amplifier audio frequency, FM tuner, tuner setup unit. I refused medium waves, since this is completely irrelevant now. Let's look at the receiver block by block.

TUNER

The tuner is assembled on the TEA5711 chip from Phillips. Possesses very good characteristics, has a built-in stereo decoder. The receiver circuit contains a minimum of radio components, the inductors are frameless without cores, they are not difficult to manufacture.

Schematic diagram tuner.

Winding data.

L1 - contains 7 turns. L2 - contains 9 turns. L3 - contains 7 turns.

All coils are wound with wire with a diameter of 0.5 mm, on a mandrel with a diameter of 3 mm.

L1 - input circuit, L2 - UHF circuit, L3 - local oscillator circuit (sets the range of received frequencies).

DIGITAL SCALE

The digital scale of the receiver is made on specialized chip LC7265. Which, however, is a frequency meter with the ability to set the IF frequency. It works in tandem with the LB3500 chip, which is a frequency divider.

Schematic diagram of a digital scale Appearance digital scale

The indicators used in the digital scale are I22B, YDD-056AO, TOD-5263BE/G, I used DA56-11EWA.

The scale input is connected to the local oscillator output on the TEA5711 chip, to pin 23.

VOLUME, TONE, BALANCE CONTROL

The regulator is made on a new microcircuit domestic production KR174XA54 from Angstrom.

Schematic diagram of the regulator. Appearance of the regulator.

AF AMPLIFIER

The AF amplifier is made on a foreign A2005V microcircuit. In principle, it is used only for listening to the receiver on headphones, but you can also connect small-sized speaker systems.

Schematic diagram of the AF amplifier Appearance of the amplifier

STABILIZER

The purpose of this block is not worth explaining, everything is clear. At first I wanted to protect the stabilizer from power reversal, but then I decided to add a diode bridge, so the polarity of the voltage supplied to the receiver input does not really matter. The only thing is that the input voltage should not exceed 25V, since the stabilizer microcircuits may fail.

Schematic diagram of the stabilizer Appearance of the stabilizer

Diagram of interconnections of a radio receiver.

The radio receiver housing was used from a Japanese high-power radiotelephone. Ideal for housing small receiver boards. The boards are connected to each other by a flexible cable, the signal and antenna wires are connected by a shielded radio cable.

Reference materials on the radio receiver.

datasheet on TEA5711.

datasheet for KR174XA54

datasheet for LB3500

datasheet for A2005V

datasheet for 78L05

datasheet for DA56-11EWA

Frequency meter from the digital scale of a car radio

Schematic diagram of my version of the scale on the LC7265,

http://vitserg. /18434.html

It takes into account everything that I didn’t like in other schemes. Firstly, I was annoyed by the flickering of the numbers when changing the scale readings. The reason for this is the common resistor across all indicator segments. So I installed a "personal" resistor for each segment. The resistor value was calculated based on the condition of 8-10 mA for each segment. For red indicators and voltage 12 V resistors d.b. about 1.2 ... 1.3 kOhm. For green It is better to make more current, so resistors should be used. about 910 Ohm... 1.1 kOhm. For outputs to which two segments of indicators are connected at once, a resistor should be used. 2 times less.
Secondly, the ICs turned out to be “capricious” regarding the supply voltage. Therefore, both the LC7265 and the LB3500 have separate adjustable voltage regulators on the LM317LZ IC. The scheme for their inclusion is standard, from the datasheet. There is, however, an “ambush” here - maximum permissible voltage for each IC scale. Therefore, before installing them in the sockets, you need to set the voltage to about 6 ... 7 V, and when setting up, monitor these voltages with a voltmeter. Or recalculate the resistors in the stabilizer.
Thirdly, the conclusions with the help of which the IF values ​​are set in the AM and FM sections. Either there is an error in the table given in the datasheet, or I did not understand something. Therefore, switches in the form of computer jumpers are provided for these pins in order to be able to select the right combination levels (for VHF transistor units such as KCF-201 and others like them, all jumpers FIF1 ... FIF3 should be connected to “zero”, and a source (or emitter) follower is not needed).
For this circuit, two versions of the printed circuit board were developed: with a remote indicator, and with an indicator installed perpendicular to the main board.

A simple scheme for increasing the cutoff frequency of your frequency meter to 250 MHz.

http://ra4a. *****/lb3500.html

I encountered the difficulty of purchasing a 193 series divider, so I delved into the diagrams.

It turns out that rubles are quite cheap on our radio markets) you can buy an interesting microcircuit LB3500 . It is a frequency divider with a division factor of 8. The operating range is MHz. (It actually works up to 300MHz.)

The microcircuit has input amplifier and signal conditioner. The sensitivity is very high and reaches 50 millivolts at 250 MHz. Very low power consumption!

https://pandia.ru/text/78/652/images/image018_7.gif" width="218" height="108"> The resistor (between pins 2 and 7) can be adjusted sensitivity microcircuits, but you must keep in mind that by decreasing the resistance of the resistor you reduce the input resistance of the device.). The resistor can be removed altogether, which may cause interference to the input circuits. (I don't recommend it!)

Please note: - at frequencies below 1MHz. The chip doesn't work!

An output divider is needed to match signal levels. I advise you to assemble a circuit with a divider in the form of a remote probe and good screen.

Having made the count, we multiply the frequency meter reading by eight - this is the measured frequency.

If you get tired of making calculations on a calculator or on paper: - I suggest a simple modification of the frequency meter. To do this, all you need to do is change the reference quartz in the frequency meter! Let's do a simple calculation! - Quartz frequency is multiplied by a factor 1.25. For example, you had a resonator at 1MHz. - Then 1.000MHz. multiply by coefficient. 1.25 we obtain the frequency of the required quartz equal to 1.250MHz. Everything is very simple! You can also move the decimal point one place to the right. (In order not to get confused, it will be absolutely cool!)

By the way, in this way you can modify the frequency meter to PIC 16F84(quartz 4MHz. replace it with 5MHz.- see calculations. The controller still operates at this clock frequency. I checked - OK!).

WFM radio receiver "Clover" range 120-190 MHz from ONK.

Due to the appearance on the portal of a whole swarm of new WFM insects with the names Bumblebee, Wasp and other stinging and non-stinging honey plants and the complete absence of simple WFM receivers of this range not only on the portal, but also on the Internet, at the request of my comrades I sat down to develop a receiver of the specified range . It was named “Clover” because insects love it. Moreover, a categorical condition was set - TDA7000 should not be used due to its scarcity and high cost. First, two prototypes were made using CXA1691 microcircuits, which are widely used in Chinese-made receivers. But another condition was the frequency range - up to 190 MHz (meaning Bumblebee). This is where the problems with SHA1691 began. In short, it still worked up to 150 MHz, and after 150 MHz only a few instances worked. Then the relatively accessible and inexpensive TEA5710 microcircuit was used, designed to build a monaural high-quality FM receiver. The performance characteristics of the microcircuit exceeded the wildest expectations: it confidently operates not only up to 190 MHz, but also much higher (the heterodyne worked stably at a frequency of 232 MHz). Moreover, a receiver based on it with an antenna made of a piece of wire about 40 cm long is at least a third superior in sensitivity to the AR-8000 in WFM mode with a standard rubber band antenna.
The circuit is developed on the basis of the microcircuit datasheet. The body kit is minimal. Any linear stabilizer can be used with an output voltage of 2.7 - 4 V, and any ULF microcircuit can also be used. In the first copy of the receiver, MC34119 was used as the ULF, but in the second copy, TDA7050 was used as it provides higher quality sound and lower noise levels. When paired with Bumblebee, the sound was loud, clear and intelligible. You don’t have to install a linear stabilizer, but then when powered by salt batteries, extremely unpleasant excitation occurs through varicaps.

Electrical circuit diagram


The scheme is very simple and extremely detailed. It can be repeated by a radio amateur with less than average qualifications, provided that the manufacturing is done carefully. The printed circuit board material is foil fiberglass laminate 1 mm thick, riveted with caps made of copper wire with a diameter of 0.4 mm in designated areas. On the installation side of the parts, the holes are countersunk..
All coils are wound on the shank of a drill with a diameter of 3 mm with ordinary enameled wire with a diameter of 0.6 mm, turn to turn, followed by a slight tension after installation.
For frequency tuning, varicaps BB134 (BB133) with a corresponding control circuit were used. The tuning range is about 8 MHz.

The setup is very simple and consists of setting the desired local oscillator frequency with capacitor C16 and then tuning first with capacitor C11, and then by compressing and stretching L2 and L1 to minimize noise.
To configure, you only need a scanning receiver. Having set the frequency PM + 10.7 MHz on it (the motor of the multi-turn variable resistor R7 should be in the middle position), bring the scanner antenna as close as possible to the local oscillator circuit and smoothly rotate C16 to achieve maximum S-meter readings. This completes the setup of the local oscillator (it is highly advisable to enclose the local oscillator in a screen).
Use R7 to tune in to the PM until it is captured by the AFC system (the tuning LED will light up). Having moved away before noise appears, very smoothly adjust C11 to a minimum of noise. You can successfully apply Blaze’s “saucepan technology”. Having moved away again until noise appears, adjust by stretching - compression according to the minimum noise, first L2, then L1. Repeat the operation until the best result. This completes the setup.
This receiver does not have a noise reduction system. If desired, you can use any key with a divider (for example, proposed by REKIN for SKhA1691) controlled by a setting LED.
Details.
The printed circuit board is designed to install parts of standard sizes from 0402, which were at my disposal, to 0803. Its size is 45 x 45 mm. IF filters are ordinary ceramic orange with the letter A at 10.7 MHz, discriminator at 10.7 MHz. Trimmer capacitors – Murata 9.8-60 pF (yellow). If it is impossible to get these, you can use others that are suitable in size with the installation of additional capacitors and using for calculation resonant frequency contours engineering calculator from the portal. The inductance of the heterodyne coil is about 40 nH (0.04 µH), all the others are about 66 nH (0.066 µH).
The UHF transistor used was 2SC3356 (R25), but you can use any other one, for example BFR93 or AT41532.

PCB drawing

ZIP archive with board in LAY format

Housing and attachments.
The case used the first available multi-turn resistor - SP3-36 with a nominal value of 100 k. The speaker is turned off when plugged into the phone socket. The speaker and headphone were used with a resistance of 8 Ohms with the addition of an additional resistor with a resistance of 24 Ohms due to the fact that the TDA7050 ULF is designed for a load resistance of 32 Ohms (or 2 x 16 in the stereo version).
The power indicator was not installed, only the settings indicator was installed.
Power supply: three AAA batteries.
The results of field testing of the fully assembled receiver in the housing exceeded our wildest expectations. The sensitivity (with the telescopic antenna retracted) is the same as the AR-8000; with the antenna extended at least one knee, the sensitivity is much better than that of the AR-8000, with the antenna fully extended - the clearest sound where the scanner hisses loudly and confidently.

Device photos

Remembering Soviet times, every radio amateur began his practice with a detector radio. To be honest, I somehow missed this moment and jumped straight to multivibrators, amplifiers, etc. I never made a receiver. But many years after the start of my amateur radio career, I gained enough experience and no longer wanted to return to the detector receiver. I wanted to make a radio receiver, but it had to be of the highest quality, with electronic tuning, with frequency display, on a modern element base and for a modern, current frequency range. As a result, Hi-Fi was supposed to appear FM tuner.

The modern element base for the tuner was not particularly pleasing, but at the same time, there was still plenty to choose from. Selected several chips Sony and Philips, compared the characteristics, circuit design, design options, and in the end the choice fell on the Philips chip - TEA5711.

FM tuner assembled according to a block diagram, each module on its own board, this was done specifically to allow them to be easily replaced. The tuner has five blocks - the tuner itself, a frequency meter, an electronic volume and tone control unit, a low-frequency amplifier and a stabilizer unit.

Tuner

Tuner, as mentioned, is made on a Philips TEA5711 chip. All the necessary components are assembled on the chip, there is a built-in voltage stabilizer with a very wide range of supply voltages from 2.1V to 12V, a stereo decoder, etc. The microcircuit does not have many external mounted radio elements, several frameless inductors.

As you can see, the tuner is not very complicated, the only inconvenience is the pin spacing of the microcircuit - 1.778mm for the SDIP32 case; SOT232-1 and 1.27mm for SO32 case; SOT287-1.
For tuning, a multi-turn slide resistor SP3 was used, but I would recommend using a precision one made by Vishay, SR Passives and the like.
Winding data of inductors.
coil L1 and L3 - contain 7 turns each; L2 - 9 turns. The coils are wound on a mandrel with a diameter of 3 mm using PEV-0.5 wire

Frequency meter

The frequency meter is made on a Sanyo LC7265 microcircuit - which is a frequency meter with subtraction of the IF value. The LB3500 frequency divider works in tandem. The IF frequency for the FM (FM) range is set by jumpers FIF1-FIF3 (pins 11, 12, 13), and for CB (AM) by jumpers AIF1, AIF2 (pins 14 and 15). In this case, the IF frequency for FM is set to +10.7 MHz.

For the display, it was recommended to use seven-segment LED indicators I22B, YDD-056AO, TOD-5263BE/G with a common anode; I was able to find inexpensive DA56-11EWA. The display is soldered on a separate board and connected to the counting board with a flexible cable. The UHF is also assembled on a separate board - it should be located as close as possible to the IF path of the tuner, so the board is soldered directly near leg 23 of TEA5711.

Volume and tone control

Actually the whole tuner has already been assembled and can be said to be ready for use, but I wanted to add a small AF amplifier to be able to connect headphones, but naturally, there is a need to adjust the volume. Just lying around idle was the K174XA54 chip - a single-chip electronic volume, tone and balance control. All control is carried out by 4 buttons, and the mode is indicated by 4 LEDs.

The regulator is designed as a single complete device; a microcontroller is not required for control via the I 2 C bus. In addition, technical specifications- nonlinear distortion coefficient is only 0.05%

AF amplifier

As mentioned earlier, an AF amplifier is only needed for listening to headphones. High powers for headphones are not required, so a cheap and affordable TDA2005 chip was chosen, which was also already available. According to the datasheet, the TDA2005 is capable of delivering 10W of power per channel with a load of 2 Ohms at a supply voltage of 14V. In our case, the supply voltage is 8V, and the load is 32 Ohms, this is quite enough for more than high volume. If desired, you can connect small-sized passive speaker systems instead of headphones.

Homemade radios

Lyzhin. R.
Radioconstructor 2000, No. 4, pp. 6-10

Modern element base allows you to create your own radio receivers with sufficient high-quality sound and high volume. The author of this design offers another FM stereo radio receiver circuit diagram made on accessible elements and equipped with the following functions: digital tone control and volume control, a stereo amplifier made using a bridge circuit, a stereo decoder with a small amount of external “body kit”.

General characteristics of the radio receiver:
Sensitivity........ 6 µV
Frequency range......... 70... 10,000 Hz
Stereo separation......................... 40 dB
Tone control range.............. +- 18 dB
Nominal output power into 2 Ohm load................... 6 W
Maximum output power................ 12 W
Total SOI at rated output power............ not more than 0.8%
Supply voltage............ 10...15 V

The radio receiver circuit itself conventionally consists of several parts:

Radio receiving path

The radio receiving path is made on the common KS1066XA1 microcircuit (its full analogue of K174XA4).
The peculiarity of this microcircuit is that its radio receiving path is made according to a low IF circuit (60... 70 kHz), comparable to the bandwidth of the radio station and therefore there is no need to use an input circuit and circuits in the IF path since these functions are performed by active RC filters on operational amplifiers included in the microcircuit. The only winding product when using this microcircuit is a heterodyne circuit controlled using a varicap.
The heterodyne coil is frameless, wound with PEV-0.61 wire. For the range 87....108 MHz, only 4 turns are needed. The coil is wound on the shank of the M3 drill. After which the resulting “spring” is removed from the drill and soldered into the board. The coil is adjusted to the required range by compressing and unclenching the turns.
The role of the antenna here is played by a piece of wire or a telescopic antenna.
The diagram of the radio receiving path is shown in Figure 1.

Stereo decoder

The stereo decoder circuit is shown in the same Figure 1. It is made on the A2 KA2263 chip (analogues of TA7343, AN7420). Setting up the stereo decoder is minimal - it boils down to the fact that it is necessary to achieve the “stereo” mode with the tuning resistor R8 when the radio station is tuned. When the decoder is operating in stereo mode, the VD2 LED starts to light.

Adjusting volume and tone

The volume and tone control unit is made on a specialized A3 K174XA48 microcircuit (its analog A1524 can also be used). Adjustments are made electronically (by changing the level DC voltage at the entrances). This eliminates the need to use dual variable resistors for synchronous level adjustments in different channels. The diagram of the volume and tone control unit is shown in the figure.
The volume is adjusted by resistor R12, stereo balance by resistor R13, timbre by resistor R15 for low frequencies, and by R14 for high frequencies.
Output signals are taken from pins 11 and 8.

Bass amplifier

The bass amplifier is made on four K174UN14 microcircuits connected in a bridge circuit. An analogue of this microcircuit is TDA2003.

Structurally, the entire device is made on several printed circuit boards ah (separately for each module). This design solution made it possible to simplify the assembly of the entire product and its configuration.
Sketches of printed circuit boards are shown in the figures:

If you are interested in more detailed information then you can look at it in the source magazine by downloading it from our library.

Receiver sensitivity is -100 µV, current consumption does not exceed 8 mA. Two A316 elements are used as power sources. The antenna is a piece of wire 20..30 cm long. When unfavorable conditions reception, the antenna length can be increased to 1... 2 m. To listen to broadcasts, you can use stereo phones with voice coil resistance DC 40...100 0m. The input signal, isolated by circuit L1C1, tuned to the middle frequency of the VHF range (69.5 MHz), is amplified by an aperiodic amplifier on transistor VT1 and, through capacitor C5, is fed to the input of the detector on transistors VT2, VT3.

The complex stereo signal (CSS) isolated by the detector from the volume control R6 through capacitor C10 is fed to the input of the CSS amplifier using transistors VT4, VT5. The KSS subcarrier frequency is restored by the L6C11 circuit, tuned to a frequency of 31.25 kHz. The KSS amplifier is covered by deep DC feedback through resistors R9, R10 and capacitor C12. Thanks to this connection, the DC operating mode of the KSS amplifier and subsequent stages galvanically connected to it is set automatically. From the output of the amplifier, the KSS goes to. input of a polar detector assembled on germanium diodes VD1 and VD2.

The subcarrier frequency of the CSS detected by the polar detector is filtered by capacitors C 13 and C14. Emitter followers on transistors VT6 and VT7 match the high output impedance of the polar detector with the low impedance of stereo phones. The base currents of transistors VT6 and VT7 flow through the polar detector diodes, resulting in a small bias voltage across them. This mode of operation of the polar detector makes it possible to reduce nonlinear distortions during detection, as well as eliminate the “mono-stereo” switch from the polar detector circuit when receiving monophonic transmissions. The functions of transistor VT1 can be performed by any transistor of the GT311 series. KT315A transistors can be replaced with any low-power high-frequency silicon transistors with a limiting generation frequency when switched on according to a circuit with an OB of at least 200 MHz.

With such a replacement, you may need to select resistor R3. To do this, a variable resistor with a resistance of 4.7 kOhm is soldered in its place and the coil trimmer L5 is set to a position in which it is inserted 1/3 of the length of the frame. By changing the resistance of the variable resistor, the generator operating mode is set to close to generation failure. In stereo phones, this will produce a lot of noise. After this, a constant one with a similar value is installed in place of the variable resistor. Transistors VT4 - VT7 can be replaced with any low-power silicon transistors. corresponding structure, having a static current transfer coefficient of at least 60.

The spread of this parameter for transistors VT6 and VT7 should not exceed 30%. Coils L1, L3 and L5 contain, respectively, 7, 5 and 7 turns of PEV-2 0.62 wire, wound on 600NN ferrite rods with a length of 12 and a diameter of 2.8 mm. The winding pitch of coils L1 and L5 is 1.5 mm, L3 - 2 mm. Coil L2 contains 15 turns of PELSHO 0.1 wire wound on the body of resistor R2. Coil L4 contains 8 turns of PEV-2 0.62 wire, wound on a brass (or aluminum) rod with a diameter of 4 mm and a length of 10 mm. Before winding, the rod must be wrapped in two layers of writing paper. The winding pitch is 1 mm. The L6 coil is wound on a movable cardboard frame, placed on a piece of round (diameter 8 mm) or rectangular (20 x 3 mm) ferrite rod 400NN or 600NN, length 60...120 mm. Its winding should contain 130... 150 turns of PEV-2 0.18 wire, evenly distributed over a 25 mm long frame.

Literature: Nikolaev A.P., Malkina M.V. - 500 schemes for radio amateurs. 1998.