The simplest tube receiver (11 photos). Homemade Low Voltage Radio How to Make Your Own Retro Electronics
A homemade receiver always works better. His music is more soulful to listen to, and even the news and weather always make me happy. Why is that? Don't know.
Turn the volume control, the power transformer clicks and shudders. There is complete silence for several seconds. Finally, at the base of the radio tubes, red dots, these filaments, flare up. They are already clearly visible at the top of the glass flasks. In a dimly lit room, a structure resembling an alien city comes to life. The growing noise in the speakers is clogged with foreign speech and music. How long ago it was. Perhaps it will be tomorrow.
There must be a lamp left in the receiver. I'll do it on her low frequency amplifier. The tube sound should remain, it is incomparable with other sound.It is desirable that some part of the receiver be made according to a direct amplification circuit , because this is history itself, all radio amateurs started with such designs, initially radio receivers were assembled according to this scheme. And there must be a medium wave range; with its maximum availability at night and in the evening, it can receive stations from Europe. Of course, the range on short waves is better, but I don’t want to complicate everything. It just so happens that medium and short waves are the main source of mobile information, which has never let me down. On these bands, I previously learned about the Chernobyl accident and the events in Moscow in 1991, when the VHF band froze, transmitting classical music.
It's decided it will be medium wave range, the path of this range itself will be executed according to type 3 direct amplification circuit -V - 2. For two centuries, I have been haunted by the dream of making a direct amplification receiver that works no worse than a superheterodyne type receiver. With the advent of some modern materials it became possible, although labor-intensive, but the latter never stopped me, this is what creativity is all about. The circuit for the high-frequency part will be made using transistors, and the low-frequency amplifier will be made using a combined lamp (two lamps in one bulb).
There is no way to do without high-quality music programs with frequency modulation. Therefore, there will definitely be an FM band (88 – 108) or the former domestic VHF band. For simplicity, you can use a ready-made superheterodyne high-frequency unit from a pocket receiver by connecting the output of its frequency detector to a low-frequency tube amplifier, but you can also go the hard way, we’ll decide as we go.
Thus, in one package you will get a medium-wave direct amplification receiver using transistors, an FM superheterodyne made on a microcircuit, and a general tube sound amplifier. No one will see the transistors and microcircuits, only the radio tube will catch the eye, and, demonstrating the design, I will say:
Look, they knew how to do it before, just one radio tube, and how many stations it receives! And what a sound! Just listen...
Let's get started first part of the project.
Three-stage selective high-frequency amplifier.
Scheme.
A special feature of the circuit is the presence of tunable circuits in all three high-frequency amplification stages. Here, a three-section variable capacitor block from an old radio is fully used. But it was still not enough for the input circuit, and therefore the preselector is broadband, consists of a concentrated selection filter, made on a ferrite rod, which is also the magnetic antenna of the receiver. Initially, I wanted to abandon the magnetic antenna and use only an external one, as in the old designs. But today, practice has shown that it is impossible to do without a magnetic antenna, which has a radiation pattern and, therefore, is capable of cutting off unnecessary interference. Wired Internet, cell phone chargers, cheap voltage converters of other electronic devices completely “kill” the mid-wave range with their emissions at these frequencies.
Each stage operates in a mode that provides a stable gain, thanks to the use of negative feedback, a cascode circuit for switching on the second stage, incomplete inclusion of the circuits and the presence of resistors in the collectors of the transistors, dampening their gain and reducing the mutual influence between them during the tuning process, as well as separate additional filters on nutrition. Experience shows that a multistage tunable high-frequency amplifier is prone to self-excitation and unstable operation, and therefore all measures have been taken, in my opinion, to ensure normal operation of the amplifier.
Structurally, each amplifier stage is covered with a screen, and each coil is made in a screen, and the screen itself is made in the form of a coil, to emphasize the retro style.
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| Sketch of the coil in the screen. |
To test the high-frequency amplifier, an external power supply of 3 to 9 volts is used. As a low-frequency amplifier, you can connect an amplifier based on the TDA 7050 microcircuit, which is in the article “High-impedance telephone for a detector receiver.”
Immediately the result was receiver 3 - V -1.
Adjustment.
The receiver will work immediately, but needs a little adjustment. Having tuned to a radio station in the upper part of the range, we achieve maximum volume with subscript capacitors, and at the bottom of the range we fix pieces of ferrite with a compound next to the coils at the maximum reception volume.
If the receiver is unstable and prone to self-excitation, then it is necessary to increase the values of resistors R5; 9;11 -13, or the value of capacitor C13, or add such a capacitor to the following stages.
After adjustment, I measured the receiver bandwidth at three decibels. At the bottom of the range it turned out to be 15 kilohertz, at the top 70 kilohertz. Sensitivity from input external antenna no worse than 200 microvolts and 20 microvolts in range, smoothly improves with increasing frequency, which corresponds to a receiver of both the third and highest classes, according to
GOST 5651-64.
In order not to upset myself, I decided not to measure selectivity (selectivity) on the adjacent channel. I left the acuity of sensations for field testing. I decided to just make sure how two powerful radio stations would be received:
1. RTV - Moscow region 846 kHz, 75 kW, 40 km from the test site.
2. Radio of Russia 873 kHz, 250 kW, more than 100 km.
After all, the separation between them is only 26 kHz. The first radio station is heard perfectly, there are no gaps in the neighboring station. When listening to the second radio station, the rating is four, if you listen closely, you can hear the gaps from the first. This is the most unpleasant place in the entire receiver.
Radio Liberty is confidently received with a transmitter power of 20 kW, located more than 130 km from the site. In the evening the range comes to life, radio stations from Ukraine and Belarus are received.
Tuning into radio stations is qualitatively different from superheterodyne receivers, since there is no noise between stations. If the turned on receiver is not tuned to a station, then it seems that it is not working.
Why I did all this, I don’t know. It’s just that now I have a radio receiver in one single copy, with a unique design, with a soulful sound, with memories of childhood and youth.
To be continued, we still have to assemble a tube amplifier.
Some of the photographs showing the manufacturing process are located at the end of the article.
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Addition. September 2012.
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| Magnetic antenna on a ferrite rod. |
Project "Vintage"
The idea of creating a media center for a summer residence was born quite a long time ago. I decided to take an old Soviet radio as a basis. Well, I am drawn to everything Soviet, you can see this by looking at the post with my previous development.
I received the radio from the Riga VEF plant in excellent condition. And if you consider that this same radio was produced in 1965, then the project simply had to be implemented.
What is noteworthy is that the radio was in full working order. And we even experimented a little with connecting an electric guitar to it.
Let's start smoking. Breaking is not building)))
Friends came to the rescue.
Don’t feed them bread at all, just give them something to sort out.
And now our device is nothing more than a wooden box.
At first there was an idea to place it inside car speakers and a homemade/purchased amplifier, but then it was decided that it would be easier and cheaper to buy a 2.1 system, for which we went to a computer store.
To implement the project, an acoustic system from Logitech was chosen for its ideal price-quality ratio.
The insides will be from a very old, but working computer.
In general, the concept is based on preserving completely original look with modern filling. In my case, the appearance will differ from the original only in the bass reflex built into the side wall and the 15" LCD monitor in the regular place of the vinyl player.
I cut out part of the glued timber and make a hole for the future bass reflex.
For proper sealing between the body of the radio and the subwoofer, I glue a rubber sealing ring. I cut it out of a record player cover. Despite its age, the rubber is very soft and elastic.
Embedding the speakers into the facade was one of the most labor-intensive processes. Due to the completely glued body, remove decorative fabric It didn't seem possible. I had to make a cut in the part covered by the original plug and very carefully mill it out seats without damaging the textiles.
From an outer corner purchased at a hardware market, I cut decorative overlay to the monitor.
After all parts of the decorative frame were adjusted, it was glued with PVA and opened with varnish.
Meanwhile, I set about implementing management. The old but working keyboard was completely disassembled. Using an improvised tester (power supply + light bulb), the contacts responsible for certain buttons were calculated. Because the system will work on the "Mediaportal" program; control requires only seven buttons.
A friend came to help with soldering the so-called “i-Bar”.
We were unable to identify all the buttons correctly at once. Of the seven buttons, only three performed necessary actions. We double-checked the contacts and re-soldered the buttons.
Three more times I had to cut and re-glue the microbuttons themselves.
Later I transferred the diagram and buttons to another, more aesthetic block.
Installation work with a telephone connected to the speaker for sound control.
Well, how could we do without it...
Construction of the building
To make the body, several planks were cut from a sheet of treated fiberboard 3mm thick with the following dimensions:
— front panel measuring 210mm by 160mm;
- two side walls measuring 154mm by 130mm;
— upper and lower walls measuring 210mm by 130mm;
— rear wall measuring 214mm by 154mm;
— boards for attaching the receiver scale measuring 200mm by 150mm and 200mm by 100mm.
The box is glued together using wooden blocks using PVA glue. After the glue has completely dried, the edges and corners of the box are sanded to a semicircular state. Irregularities and flaws are puttied. The walls of the box are sanded and the edges and corners are sanded again. If necessary, putty again and sand the box until a smooth surface is obtained. We cut out the scale window marked on the front panel with a finishing jigsaw file. Using an electric drill, holes were drilled 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 (automotive primer in aerosol packaging) in several layers until completely dry and smooth out the unevenness 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 with inside front panel. Finally, we try on the back wall and install the necessary connectors on it. We attach plastic legs to the bottom using double tape. Operating experience has shown that for reliability, the legs must either be firmly glued or fastened with screws to the bottom.
Holes for handlesChassis manufacturing
The photographs show the third chassis option. The plate for fastening the scale is modified to be placed 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 cross-section of 25 mm by 10 mm. The bars secure the back wall of the box and the scale mounting panel. Posting nails and glue are used for fastening. A horizontal chassis panel with pre-made cutouts for placing a variable capacitor, 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
prototyping did not work for me. During the debugging process, I abandoned the reflex circuit. With one HF transistor and a ULF circuit repeated as in the original, the receiver started working 10 km from the transmitting center. Experiments with powering the receiver with a low voltage, like an earth battery (0.5 Volts), showed that the amplifiers were insufficiently powerful for loudspeaker reception. It was decided to increase the voltage to 0.8-2.0 Volts. The result was positive. This receiver circuit was soldered and in a two-band version installed at a dacha 150 km from the transmitting center. With a connected external stationary 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 went into self-excitation mode, which forced the device to be adjusted depending on the air temperature in the room. I had to study the theory and make changes to the scheme. Now the receiver worked stably down to a temperature of -15C. The price for stable operation is a reduction in efficiency by almost half, due to an increase in the quiescent currents of transistors. Due to the lack of constant broadcasting, I abandoned the DV band. This single-band version of the circuit is shown in the photograph.
Radio installation
Homemade printed circuit board receiver is made according to the original circuit and has already been modified in field conditions to prevent self-excitation. The board is installed on the chassis using hot melt adhesive. To shield the L3 inductor, an aluminum shield connected to a common wire is used. The magnetic antenna in the first versions of the chassis was installed in the upper part of the receiver. But periodically they put it on the receiver metal objects And Cell Phones, which disrupted the operation of the device, so I placed the magnetic antenna in the basement of the chassis, simply gluing it to the panel. The KPI with an air dielectric is installed using screws on the scale panel, and the volume control is also fixed there. The output transformer is used ready-made from a tube tape recorder; I assume that any transformer from a Chinese power supply will be suitable for replacement. There is no power switch on the receiver. Volume control is required. At night and with “fresh batteries,” the receiver begins to sound loud, but due to the primitive design of the ULF, distortion begins during playback, which is eliminated by lowering the volume. The receiver scale was made spontaneously. The appearance of the scale was compiled using the VISIO program, followed by converting the image into a negative form. The finished scale was printed on thick paper using a laser printer. The scale must be printed on thick paper; if there is a change in temperature and humidity, the 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 burnt-out Chinese transformer. The arrow is fixed on the axis with glue. The tuning knobs are made from soda caps. Pen required diameter Simply glue it to the lid using hot glue.
Board with elements Container with batteries
As mentioned above, the “earthen” power option did not work. As alternative sources It was decided to use dead “A” and “AA” format batteries. The household 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” format battery from September to May. A container is specially glued to the back wall for power supply from AA batteries. Low current consumption requires the receiver to be powered from solar panels garden lanterns, but for now this issue is irrelevant due to the abundance of “AA” format power supplies. The organization of power supply with waste batteries led to the name “Recycler-1”.
Loudspeaker of a homemade radio receiver
I do not advocate using the loudspeaker shown in the photograph. But it is this box from the distant 70s that gives maximum volume from weak signals. Of course, other speakers will do, but the rule here is that the bigger the better.
Bottom line
I would like to say that the assembled receiver, having low sensitivity, is not affected by radio interference from TVs and switching power supplies, and the quality of sound reproduction differs from industrial AM receivers cleanliness and saturation. During any power failures, the receiver remains the only source for listening to programs. Of course, the receiver circuit is primitive, there are circuits of better devices with economical power supply, but this homemade receiver works and copes with its “responsibilities”. Spent batteries are properly burned out. The receiver scale is made with humor and gags - for some reason no one notices this!
Final video
Once upon a time, we assembled our first simple radios at school age from kits. Today, due to the development of modular design, it is not difficult to assemble a digital radio receiver even for people who are extremely far from amateur radio. This receiver's design is based on the impressive 1935 AWA radio that the author came across in the book Deco Radio: The Most Beautiful Radios Ever Made. The author was so impressed by its design that he wanted to have his own analogue.
The design uses a Nokia 5110 LCD display to display the frequency and an encoder to select it. The volume is controlled by a variable resistor built into the amplifier. To emphasize the design, the author also used an Art Deco style font to display information on the display. The Arduino code contains a function for remembering the last station listened to (which was listened to for more than five minutes).
Step 1: Components
- Arduino Pro Mini
- FTDI programmer
- TEA5767 FM radio module
- Speaker 3W
- PAM8403 amplifier module
- Encoder
- Nokia 5110 LCD display
- Battery charge and protection board
- 18650 battery
- Holder 18650
- Switch
- Breadboard 5x7 cm
- Connecting wires
- Speaker fabric
First of all, if you don't have great experience When working with Arduino, you should first assemble the circuit using a non-printed breadboard. In this case, for convenience, you can use Arduino Nano or UNO. Personally, I use Arduino UNO at the stage of debugging circuits, since it is convenient to use it together with a breadboard for connection necessary components, practically without using soldering. When you turn on the device, the logo should be displayed on the screen for a few seconds, after which the frequency of the last listened station is loaded from the EEPROM memory. By turning the encoder knob you can adjust the frequency by changing stations.
When everything works well on the breadboard, you can move on to the main assembly, using the more compact and cheaper Arduino PRO Mini, which, moreover, has lower consumption. But before that, let's see how everything will be located in the case.
Step 3: Design the Case
The 3D model was developed in the free but quite powerful Fusion 360 program.
Step 4: 3D Printing and Processing
FormFutura "wooden" plastic was used for printing. This is a rather unusual plastic, the peculiarity of which is that after printing the parts have a look similar to wood. However, when printing with this plastic, the author encountered a number of problems. Small parts printed without problems, but the body, the largest part, did not print the first time. When trying to print it, the nozzle constantly became clogged; the situation was aggravated by regular power outages, which is why the author even had to purchase a UPS for the printer. Ultimately, the body was overprinted on top of the unprinted blank. This solution, however, is not really a solution to the problem, just a one-time way out of the situation, so the question remains open. Since the print did not work out successfully, the author then decided to sand the body, putty it with wood putty and varnish it. Yes, this plastic doesn’t just look like wood, it’s essentially fine wood dust mixed with a binder plasticizer, so the parts printed with it are practically wooden and can be processed using ordinary wood.
Step 5: Putting it all together
The next step is to install the electronics into the housing. Since everything has already been modeled in Fusion 360, this won't be a problem. As you can see, each component has its own position in the case. The first step was to unsolder the Arduino Pro Mini, after which the code was loaded into it. The next step is the power source. The project used a very convenient and compact Wemos board, which is simultaneously responsible for charging the battery, protecting it, and also increases the voltage for consumers to the required 5 volts. Instead, you can use a conventional charge and protection module, and increase the voltage with a separate DC/DC converter (for example TP4056 + MT3608).
Next, the remaining components, speaker, display, and amplifier are soldered. Also, even though there are power supply capacitors on the amplifier module, it is advisable to add another one (the author set it to 330 uF, but 1000 is also possible). The sound quality (if 10% THD can be called quality) of the sound of the PAM8403 amplifier very much depends on the power supply, as does the operation of the radio module. When everything is soldered and tested, you can start final assembly. First of all, the author glued the grille and radio fabric on top of it.
Push. Radio fabric is a specific thing, and every stall does not sell it. However, in every women's needlework store you can buy such a thing as canvas (fabric for cross stitch). It is inexpensive and very suitable as a replacement for radio fabric, sometimes different colors. Take natural (not synthetic) and with the largest cell. By the way, it fits perfectly with the design of this radio.
All other boards are fixed in place using hot-melt adhesive. You can use hot glue a lot, but it works really well for these purposes, considering that most modules do not have mounting holes. Although I prefer to use double-sided "car" tape for these purposes.
Step 6: Firmware
This step should have been placed higher, since it needs to be flashed at the debugging stage. The basic idea of the code is this: when the encoder knob is turned, the frequency is searched, when the encoder knob remains in the same position for more than 1 second - this frequency is set for the FM receiver module.
If(currentMillis - previousMillis > interval) ( if(frequency!=previous_frequency) ( previous_frequency = frequency; radio.selectFrequency(frequency); seconds = 0; )else
The FM radio module takes about 1 second to tune to a new frequency, so it will not be possible to change the frequency in real time by turning the encoder knob, because in this case, the receiver tuning will be very slow.
My friend asked me to build a simple radio for him with his own hands in a certain theme. He looked at several options I suggested, and we agreed on the theme of Guinness beer.
Guinness is an Irish draft beer, its emblem is a golden harp. We decided that the central place in the design of the radio would be given to this harp, and we decided to omit the text.
After drawing several sketches, we came to the conclusion that the most successful shape was the “tombstone” shape. Having chosen the shape, we began to design and assemble a vintage MP3 radio.
One of the main tasks was the built-in subwoofer. I used the speakers from 2.1 computer speakers, I ordered the MP3 module on eBay.
List of materials used for a homemade radio:
- computer speakers 2.1
- power supply 12V 1A AC-DC (for MP3 module) - step-down converter
- mp3 decoder
- rotary switch (for lamps)
- FM antenna (built into the MP3 module)
- gold caps for volume, bass and power switches
- gold foil and glue
- two-way adhesive tape on a foam base, wires and various auxiliary materials
Step 1: Design and Assembly
Since I disassembled the speakers to get the speakers out of them, I know what the internal volume of the subwoofer in the radio needs to be made, and based on this, calculate the dimensions of the radio housing.
I sketched it in Sketchup to work out the model and get the dimensions of the parts. Unfortunately, I did not find the software model, so I could not attach it to the article.
When the contours of the parts are applied to the wood, cut out the parts with a jigsaw or openwork saw.
I always cut out the parts with a margin so that I can sand off the excess wood to get the shape out.
I made the front panel larger than the back wall so that the place where the radio housing was attached to the front panel was not visible.
The subwoofer speaker is enclosed in an inner box and removed through a hole in the rear wall. I left the original cardboard tube from a computer speaker.
Step 2: Milling
When the parts you cut out are polished and brought to the right sizes, you can start milling parts to complete them appearance and for product assembly.
In the front panel, on the inside, you need to machine a groove into which the radio housing will be attached; we mill the back wall to create an overlapped joint to make the connection between the back wall and the housing invisible.
We process the edges of the internal hole and the base of the receiver in the front wall with a cutter with an S-shaped profile. The outer edge of the front panel is simply rounded.
One of the tasks in the manufacture of the radio receiver was sufficient endurance - the housing must withstand the load of a working subwoofer.
I processed the edges of the box parts with a straight router attachment so that they overlap. I glued the joints, and additionally fastened the parts with nails without heads.
Because of vent The subwoofer comes out through the back wall, the ventilation tube had to be placed in a box, so I cut out the place for gluing the subwoofer with a straight bit for a router.
Step 3: Decorative Lattice
The inside of the front panel will need to be ground down to a thickness of 3 mm with a router so that the decorative grille can be installed flush with the rear surface of the panel. To do this I again used the straight router bit.
I cut out the pattern of the decorative lattice in a larger contour around the perimeter; the pattern from the template was transferred to the wood with an X-acto knife.
The contour of the harp is cut from oak plywood on jigsaw machine. To make thin strips of string I used a nail file.
Step 4: Install the electrical wiring
Show 5 more images
Before fixing all the components in place, you need to perform a test assembly. After all the glued joints have dried, the wood must be covered with stain and finishing compound.
Using a straight cutter, cut out holes for the on/off, volume and bass knobs.
Make two plywood boards - one to cover with fabric (it will serve as a background for the harp) and the second to attach the speakers to decorative grille. Attach the MP3 module to the grille with screws.
Now you need to connect all the components to each other, power from the converter to the amplifier, power from the adapter to the MP3 module, connect the MP3 module to the amplifier, to the speakers and the FM antenna to the MP3 module.
The converter is quite heavy, so I screwed it to the cover of the amplifier box; I attached the rest of the circuits to the cover of the amplifier box on double-sided foam adhesive tape.
Step 5: Cover the wood with stain and cover the harp with foil
The base, front panel and back wall are covered with two thin layers of Minwax stain and three very thin layers of polyurethane primer.
Cover the decorative grille with black spray paint. After covering the harp figure with glue, place a sheet of foil on top. Using a wooden ice cream stick (or other tool with a smooth edge), smooth out the foil so that it sticks well. We lift the sheet, now we can see that the harp on the grille is covered with gold metal. Just in case, I coated the harp with a layer of primer to prevent the foil from peeling off.
Before gluing the foil, make sure that the surface of the adhesive is smooth - the foil will show the slightest unevenness. The photo shows that the foil on the harp emphasizes the rough texture of the surface underneath.
Step 6: Pine Veneer Cladding
Due to the fact that my retro receiver has a subwoofer and is quite large in size, I decided that it needed to add a horizontal link between the front panel and back wall. I processed the edges of this bundle with a milling cutter so that the parts of the body were attached to it overlapping.
After that I decided to add side pieces to the receiver body. The pieces of wood for the rounded segments of the body have cuts on the inside and with the help of a soap solution (soak for about 20 minutes) they can be bent and installed in place. I additionally glued the places where they were attached to the walls and secured them with nails without a head.
When the body assembly is completed, we unroll the veneer so that it can “rest.” After this, we glue the veneer around the perimeter of the body (I used veneer on adhesive based) and cover the already treated areas of wood with masking tape, and in the same way cover the veneer with two layers of stain and three layers of primer.
Remove the masking tape and the radio is now ready.