Do-it-yourself radiola case. Homemade radio receiver with low-voltage power supply with your own hands. Final assembly of the receiver

In the article, we got acquainted with the circuit diagram of the VHF receiver, and at the same time dismantled all the components that it will consist of. In this part, we will continue to collect simple VHF receiver Let's start with the PCB.

3. Printed circuit board of the VHF receiver.

The appearance of the receiver circuit board from the side of the tracks is shown in the figure below.

The printed circuit board is made on double-sided foil-coated fiberglass 1mm thick. The red lines show the connection of external elements: loudspeaker and antenna, and the jumper is indicated by the dotted line.

The appearance of the board from the side of the parts, as well as their location and numbering according to the schematic diagram, are shown in the following figure.

The case for the receiver is taken from children's counting sticks; paper clips are also sold in such cases. Since the board is not attached to the case, but is tightly fitted to it, the dimensions are given conditionally, since each one will have its own. Therefore, first of all, fiberglass is adjusted to the internal size of the case, and only then holes for parts are marked and drilled on it.

4. Receiver housing.

When all the details are installed on the board, the next step is to make holes in the side of the case for the tuning knob, power switch and volume control. And in order to mark the holes more accurately, the side wall template is made of paper.

When performing a vertical measurement, the board is placed on a flat surface, relative to which the measurement is made. Thus, the height of the solder and the legs of the parts that protrude from the PCB side and raise the board above the surface by 1-3 mm are taken into account.

The finished template is applied from the inside of the case, and the markings are transferred from the outside with a thin marker, and holes are drilled with a thin drill according to the outlined pattern.

Before you cut holes with a needle file, you need to remove the jumpers between them. This can be done like this: a fixed drill in the chuck is inserted into the central hole and the drill is turned on. When the drill starts to rotate, the drill handle is moved to the left and right sides, while the drill cuts off the jumpers with its cutting edge. And in order not to break the drill, the drill is moved gradually and without pressure, as the drill cuts off the jumper.
And after the jumper is removed, you can freely work with a needle file in both directions.

After the final processing, you should get something like in this picture:

5. Receiver setup.

Assembled without errors and from serviceable parts, the receiver, as a rule, starts working immediately, but for better tuning at the radio station, it needs to be adjusted a little. The whole setting comes down to fitting the inductance of the coils of the input and heterodyne circuits. For the first setup of the receiver, you will need some kind of power source, for example, this one.

First, coil L2 is stretched to a length of 7 ... 10 mm, and then coil L1 is stretched to a length of 4..5 mm. Perhaps, in the process of tuning to the radio station, the length of each coil will have to be slightly adjusted (when the turns are stretched, the inductance of the coil decreases, and when narrowed, it increases.

Instead of the antenna, we solder a piece of stranded mounting wire 600-800 mm long and apply a 3V supply voltage to the receiver. By moving the engine of the variable resistor R3 from one extreme position to another, we are trying to catch local radio stations.

The main tuning for the selected range is performed by the L1 coil. It has been experimentally established that with a decrease in the length of the coil, the range of 88-108 MHz is evenly distributed along the entire length of the resistor R3. You can see the range setting in the video at the end of the article.

6. Final assembly of the receiver.

After setting up the receiver, we make the final assembly of the case, and it remains for us to assemble the compartment for galvanic cells. The compartment elements are attached when the board is in the receiver case, since after the compartment is assembled, the board cannot be pulled out.

The power compartment is made of three plates cut out of foil-coated fiberglass with a thickness of 1mm. The plates are attached to the board and to each other by soldering. For these purposes, strips of foil 4 mm wide are etched along the edges of the plates.

On one plate, two rectangles are etched, designed to remove power. A solid rectangle is etched on the second plate, which serves as a jumper between the galvanic cells, connecting them in series.

To supply voltage from galvanic cells to the circuit, there are platforms with holes on the side of the parts and tracks, which are interconnected by pieces of the mounting wire.

It may happen that the batteries are shorter by 1-2 mm. To do this, a plate of foil fiberglass is cut out and soldered from the jumper side.

It remains for us to fix the dynamic head on the front cover of the receiver. When using a case from counting sticks, the head fits freely in the UZCH area. With a 1.5mm drill, holes are drilled opposite the diffuser, and then the head is glued with Moment glue.

Now we insert the batteries and finally check the operation of the receiver. If necessary, then once again adjust the coil L1. The wire used as an antenna is conveniently routed above the external power connector.

As you can see, the design of this VHF receiver on the K174XA34 chip simple and does not present special skills and difficulties during assembly, although at first glance it seems complicated. Therefore, for a novice radio amateur, repeating this design will not be difficult. Well, if you still have questions, then be sure to watch these videos that complement the article.

Hull construction

For the manufacture of the case, several boards were cut from a sheet of ennobled fiberboard 3 mm thick with the following dimensions:
- front panel measuring 210mm by 160mm;
-two side walls measuring 154mm by 130mm;
- upper and lower wall measuring 210mm by 130mm;

- rear wall measuring 214mm by 154mm;
- plates for mounting the receiver scale measuring 200mm by 150mm and 200mm by 100mm.

With the help of wooden blocks, a box is glued using PVA glue. After the glue has completely dried, the edges and corners of the box are polished to a semicircular state. Irregularities and flaws are putty. The walls of the box are sanded and the edges and corners are re-sanded. If necessary, putty again and grind the box until a flat surface is obtained. The scale window marked on the front panel is cut out with a finishing saw of a jigsaw. An electric drill drilled holes for the volume control, tuning knob and range switching. We also grind the edges of the resulting hole. We cover the finished box with primer (automobile primer in aerosol packaging) in several layers with complete drying and level the irregularities with emery cloth. We also paint the receiver box with automotive enamel. We cut out the glass of the scale window from thin plexiglass and carefully glue it on the inside of the front panel. At the end, we try on the back wall and install the necessary connectors on it. We attach plastic legs to the bottom with double tape. Operating experience has shown that for reliability, the legs must either be glued tightly or fastened with screws to the bottom.

Holes for handles

Chassis manufacturing

The photographs show the third version of the chassis. The plate for attaching the scale is being finalized for placement in the internal volume of the box. After completion, the necessary holes for the controls are marked and made on the board. The chassis is assembled using four wooden blocks with a section of 25 mm by 10 mm. Bars fasten the back wall of the box and the scale mounting panel. Postal nails and glue are used for fastening. A horizontal chassis panel with pre-made cutouts for placing a variable capacitor, a volume control and holes for installing an output transformer is glued to the lower bars and walls of the chassis.

Electrical circuit of the radio receiver

layout did not work for me. In the process of debugging, I abandoned the reflex scheme. With one HF transistor and the ULF circuit repeated as on the original, the receiver earned 10 km from the transmitting center. Experiments with the power supply of the receiver with reduced voltage, like an earth battery (0.5 Volts), showed insufficient power of the amplifiers for loud-speaking reception. It was decided to raise the voltage to 0.8-2.0 volts. The result was positive. Such a receiver circuit was soldered and installed in a two-band version in a country house 150 km from the transmitting center. With a connected external fixed antenna 12 meters long, the receiver installed on the veranda completely sounded the room. But when the air temperature dropped with the onset of autumn and frost, the receiver switched to self-excitation mode, which forced the device to adjust depending on the air temperature in the room. I had to study the theory and make changes to the scheme. Now the receiver worked steadily down to -15C. The fee for the stability of work is a decrease in efficiency by almost half, due to an increase in the quiescent currents of transistors. In view of the lack of constant broadcasting, he refused the DV range. This single-band version of the circuit is shown in the photograph.

Mounting the radio

The homemade printed circuit board of the receiver is made according to the original circuit and has already been finalized in the field to prevent self-excitation. The board is installed on the chassis with hot glue. To shield the inductor L3, an aluminum shield connected to a common wire is used. The magnetic antenna in the first versions of the chassis was installed at the top of the receiver. But from time to time, metal objects and cell phones were placed on the receiver, which disrupted the operation of the device, so the magnetic antenna was placed in the basement of the chassis, simply gluing it to the panel. KPI with an air dielectric is installed with screws on the scale panel, the volume control is also fixed there. The output transformer is used ready from a tube tape recorder, I admit that any transformer from a Chinese power supply is suitable for replacement. The receiver does not have a power switch. Volume control is required. At night and on “fresh batteries”, the receiver starts to sound loud, but due to the primitive design of the ULF, distortion begins during playback, which is eliminated by lowering the volume. The scale of the receiver was made spontaneously. The appearance of the scale was compiled using the VISIO program, with the subsequent transfer of the image to a negative view. The finished scale was printed on thick paper by a laser printer. The scale must be printed on thick paper; when temperatures and humidity fluctuate, office paper will go in waves and will not restore its previous appearance. The scale is completely glued to the panel. Copper winding wire is used as an arrow. In my version, this is a beautiful winding wire from a burned-out Chinese transformer. The arrow is fixed on the axis with glue. The tuning knobs are made from carbonated drink caps. The handle of the desired diameter is simply glued into the lid with hot glue.

Board with elements

Receiver assembly

Radio Power

As mentioned above, the "earth" power option did not go. As alternative sources, it was decided to use dead batteries of the “A” and “AA” formats. The farm constantly accumulates dead batteries from flashlights and various gadgets. Dead batteries with a voltage below one volt became power sources. The first version of the receiver worked for 8 months on one "A" battery from September to May. A container is glued on the rear wall especially for power supply from AA batteries. Low current consumption assumes that the receiver is powered by solar panels of garden lights, but so far this issue is irrelevant due to the abundance of AA power sources. The organization of power supply with waste batteries served as the assignment of the name "Recycler-1".

Homemade radio loudspeaker

I do not urge you to use the loudspeaker shown in the photo. But it is this box from the distant 70s that gives the maximum volume from weak signals. Of course, other columns are also suitable, but the rule works here - the more the better.

Outcome

I would like to say that the assembled receiver, having a low sensitivity, is not affected by radio interference from TVs and switching power supplies, and the quality of sound reproduction from industrial AM receivers is different purity and saturation. During any power failures, the receiver remains the only source of listening to programs. Of course, the receiver circuit is primitive, there are circuits of better devices with economical power supply, but this do-it-yourself receiver works and copes with its “duties”. Spent batteries are regularly burned out. The scale of the receiver is made with humor and jokes - no one notices this for some reason!

Final video

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I tried to make this homemade VHF receiver in the retro style. Front End from the car radio. KSE marking. Next, the IF block on the KIA 6040, the VLF on the tda2006, the 3GD-40 speaker, in front of which the notch at 4-5 kHz, I don’t know for sure, I picked it up by ear.

Radio receiver circuit

I don’t know how to do digital tuning, so it will be just a variable resistor, for this VHF unit, 4.6 volts is enough to completely cover 87-108 MHz. Initially, I wanted to insert ULF on P213 transistors, since I assembled and rebuilt the "retro", but it turned out to be too bulky, I decided not to show off.

Well, a surge protector is installed, of course it does not hurt.

There was no suitable dial indicator, or rather there was, but it was a pity to put - only 2 left, so I decided to redo one of the unnecessary M476 (as in Ocean-209) - straightened the arrow, made a scale.

Illumination - LED strip. Vernier is assembled from parts of various radios, from tube to China. The entire scale with the mechanism is removed, its body is glued from many wooden parts, stiffness is given by the textolite, on which the scale is glued and all this is attracted to the receiver body, along the way additionally pressing the front panels (those with mesh), which are also removed if desired.

Scale under glass. The tuning knobs are from some junkyard radio, touched up.

In general, a flight of fancy. I have long wanted to try the curvature of my hands by building something similar. And then there was absolutely nothing to do, and the scraps of plywood from the repair remained, and the mesh turned up.

Radio receiver housing, decorative and protective elements

The acoustic characteristics of the radio receiver are determined not only by the frequency characteristics of the low-frequency path and loudspeaker, but to a large extent depend on the volume and shape of the case itself. The body of the radio receiver is one of the links in the acoustic path. No matter how good the electro-acoustic parameters of the low-frequency amplifier and loudspeaker are, all their advantages will be reduced if the radio receiver case is poorly designed. It should be borne in mind that the body of the broadcasting receiver is at the same time a decorative element of the design. For this purpose, the front part of the case is closed with a radio fabric or a decorative grille. Finally, to protect the listener from accidental damage when touching conductive parts, the chassis of the radio receiver in the housing is protected by a rear wall on which a power circuit blocking is installed. Consequently, decorative and protective structural elements that are elements of the acoustic path, as well as methods for their mechanical fastening, can have a significant impact on the quality of reproduction of sound programs. Therefore, we will consider each structural element of the broadcasting receiver housing separately.

radio housing must meet the following basic requirements: its design must not limit the frequency range regulated by GOST 5651-64; the manufacturing and assembly process must comply with the requirements of mechanized production; manufacturing cost should be low; external design is highly artistic.

To meet the first requirement, the enclosure must provide good reproduction of the low and high frequencies of the radio's audio range. For this purpose, it is necessary to make preliminary calculations of the shape of the hull. The final determination of its dimensions and volume is verified by the results of tests in an acoustic chamber.

In acoustic calculations, the loudspeaker cone is considered as a piston oscillating in the air, which creates areas of high and low atmospheric pressure during forward and reverse motion. Therefore, it is far from indifferent in which case the loudspeaker is located: with an open or closed rear wall. In a housing with an open rear wall, air thickening and rarefaction arising from the movement of the rear and front surfaces of the diffuser, bending around the walls of the housing, overlap each other. In the case when the phase difference of these oscillations is equal to n, the sound pressure in the plane of the diffuser decreases to zero.

An increase in the depth of the hull according to the design requirements is quite acceptable. The dimensions of radio receivers with several loudspeakers cannot be calculated using the above formulas. In practice, the dimensions of enclosures with multiple loudspeakers are determined experimentally from the results of acoustic tests.

The design of cases of broadcasting receivers in the desktop version with a closed back wall is usually not used. This is explained by the fact that it is very difficult and impractical to design radio receiver cases with a closed volume, since the heat exchange mode of radio components worsens. On the other hand, tightly closed back enclosures tend to increase the resonant frequency of the loudspeaker and cause uneven frequency response at higher frequencies. To reduce the uneven frequency response at high frequencies, the inner side of the cabinet is upholstered with sound-absorbing material. Naturally, such a complication of the design can only be allowed in radio receivers of the highest classes, in furniture design with remote acoustic systems.

To fulfill the second requirement for cases, it is necessary to be guided by the following considerations: when choosing a material for a case, it is desirable to take into account the standards recommended by GOST 5651-64 for amplification paths in terms of sound pressure, given in Table. 3.

Table 3

As can be seen from Table. 3, depending on the class of the radio receiver, the norms of the frequency range of the entire amplification path in terms of sound pressure also change. Therefore, it is not always advisable for all classes of radio receivers to choose high-quality materials with good acoustic properties. In some cases, this does not lead to an improvement in the acoustic characteristics of the receivers, but increases their cost, since the loudspeaker is selected in accordance with GOST standards, which determines the range of reproducible frequencies. For these reasons, there is no need to improve the acoustic characteristics of the cabinet, when the sound source itself does not provide the possibility of their implementation. On the other hand, a low-frequency path having a narrower frequency range makes it possible to reduce the cost of the low-frequency amplifier design.

According to statistics, the cost of a wooden case is from 30-50% of the total cost of the main components of the receiver. The relatively high cost of the hull requires the designer to be careful in choosing its design. What is acceptable when designing high-end radio receivers is completely inapplicable for class IV receivers designed for a wide range of consumers. For example, in radio receivers of the highest and first classes, in some cases, the walls of the case are made from separate pine boards laid between two thin sheets of plywood to improve sound reproduction. The front sides of the case are pasted over with veneer of precious woods, varnished and polished. At the same time, cheap plywood, non-deficient wood veneer, texturized paper or plastics are used to manufacture class III and IV radio receiver cases. Metal cases are not currently used due to non-

satisfactory acoustic qualities and the appearance of overtones that are unpleasant to the ear.

To analyze the design, it is advisable to use the so-called unit cost, i.e., the cost per unit volume or weight of the material. In each case, knowing the cost of the hull and the amount of material used, it is possible to determine the unit cost. Regardless of the volume of material spent on the manufacture of the case for a certain technological process of its external decoration, the unit cost has a constant specific value. For example, in the manufacture of receiver cases at a specialized enterprise or in workshops, the unit cost is 0.11 kopecks. This value of the unit cost also takes into account overhead costs: the cost of the material, its processing, finishing, wages. It should be borne in mind that the value of the unit cost of the hull corresponds to well-defined materials and technological processes. The value is 0.11 kop. refers to cases made of plywood, pasted over with cheap veneer (oak, beech, etc.) and varnished without subsequent polishing. For cases carefully polished and pasted over with more valuable wood species, the unit cost increases by approximately 60% - Thus, to determine the cost of a wooden radio case, it is necessary to multiply the unit cost by the amount of material (plywood) used.

The process of pasting the body of the radio receiver with precious woods and subsequent polishing is quite laborious, as it involves many manual operations, requires large areas for its processing and tunnel ovens for drying the treated surfaces. In order to save veneer, which is scarce for a number of enterprises, it is replaced with texturized paper, on which a pattern of wood fibers is applied. However, pasting radio receivers with texturized paper does not improve the situation, since to create a good presentation, multiple varnishing (5-6 times) is required, followed by drying.
in tunnel ovens. In addition, an additional operation is introduced - painting the corners of the body, where sheets of texturized paper are joined. The cost of buildings finished in this way does not decrease due to the high labor intensity of the work.

The choice of the thickness of the material for the walls of the case must be made taking into account the technical requirements for the acoustic system of the radio receiver. Unfortunately, the technical literature lacks detailed information about the choice of material grade and its effect on the acoustic parameters of receivers. Therefore, when designing cases, one can only be guided by the brief information presented in the work. For example, in high-end radio receivers for reproducing low frequencies of 40-50 Hz with a sound pressure of 2.0-2.5 N!m2, the thickness of the walls made of plywood or joinery boards must be at least 10-20 mm. For radio receivers of classes I and II, when reproducing low frequencies of 80-100 Hz and sound pressure of the order of 0.8-1.5 n / m2, a plywood thickness of 8-10 mm is allowed. Cases for acoustic systems of radio receivers of III and IV classes, having a cutoff frequency of 150-200 Hz and sound pressure up to 0.6 n / m2, can have a wall thickness of 5-6 mm. Naturally, it is very difficult to make wooden cases with a wall thickness of 5-6 mm, since it is impossible to ensure sufficient structural strength. Housings with small wall thicknesses are usually made of plastic, however, even in this case stiffening ribs must be provided to eliminate vibrations of the housing walls.

For economic reasons, the manufacture of plastic cases for radio receivers is more profitable than wooden ones. Despite the technological and economic advantages of plastics for the manufacture of housings, their use is limited to broadcasting receivers with large dimensions and high acoustic characteristics.

It is well known that wood has good acoustic properties, so radios

the upper classes tend to have wooden hulls. For these reasons, cases made of plastics are made only for class IV radios and very rarely for class III radios.

The body of the radio receiver must have sufficient structural strength, withstand mechanical tests for impact strength, vibration resistance and strength during transportation. The use of methods adopted in the furniture industry, i.e., the implementation of butt connections using spiked joints, is not justified by economic considerations, since the manufacturing process becomes more complicated, and, consequently, the standard time for processing and assembly operations increases. Usually, the angular interfaces of the walls of the housings of broadcasting receivers are performed by simpler methods that do not cause technological production difficulties. For example, the walls of the case are connected with bars or squares glued into the corner joints, or with the help of wooden planks inserted with glue into the slots of the parts to be joined. Wooden walls can be connected with metal squares, staples, strips, etc. And yet, despite the measures taken to simplify the technological processes for manufacturing wooden cases, their cost remains relatively high.

The most time-consuming technological processes are pasting with wood veneer, varnishing and polishing the surfaces of the case. The process of polishing the assembled body is especially difficult in corner joints, since in these cases it is impossible to avoid manual operations. It is natural, therefore, that the efforts of designers and technologists should be aimed at creating such a hull design, the manufacture of parts of which and assembly processes could be mechanized as much as possible. The most rational in this regard is the prefabricated hull design, when individual parts of a simple shape undergo final processing and finishing, and then

mechanically combined into a common structure.

Rice. 37. The design of the prefabricated body.

There are other designs of collapsible buildings. One of the domestic radio factories has developed a design in which the side walls are connected by metal panels using bolted connections. In this case, the radio receiver chassis is an independent unit, independent of the housing design.

Naturally, the above examples do not exhaust all the possibilities for developing design designs for detachable housings. One thing is obvious - such designs are the simplest and cheapest.