Fm in retro style with your own hands. The original interior design in retro style - the old radio equipment has become an accented detail and causes a kind smile. Electrical circuit of the radio receiver
Hull building
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 (automotive 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 format 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
A homemade receiver always works better. His music is listened to more sincerely, and even the news and the weather always make me happy. Why is that? Don't know.
Volume control turn, click and wince the power transformer. There is complete silence for a few seconds. Finally, at the base of the radio tubes, red dots flare up, these filaments. They are already clearly visible in the upper part of the glass flasks. In a dimly lit room, a structure resembling an alien city comes to life. The growing noise in the speaker is clogged with foreign speech and music. How long ago was that. Perhaps it will be tomorrow.
There must be a lamp in the receiver. I will do on her low frequency amplifier. The tube sound must remain, it is incomparable with other sound.It is desirable that some part of the receiver is made according to the direct amplification scheme. , 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 range of medium waves, 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 happened that medium and short waves are the main source of mobile information that has never let me down. On these bands, I had previously learned about the Chernobyl accident and the events in Moscow in 1991, when the VHF band hung, transmitting the classic music.
Decided to be medium wave range, the path of this range will be executed according to type 3 direct amplification circuit -V-2. For two centuries, the dream has not left me to make a direct amplification receiver that works no worse than a superheterodyne type receiver. With the advent of some modern materials, this became possible, although laborious, but the latter never stopped me, this is what creativity is all about. The circuit of the high-frequency part will be made on transistors, and the low-frequency amplifier on a combined lamp (two lamps in one bulb).
You can't do without high-quality music programs with frequency modulation. Therefore, there will definitely be an FM band (88 - 108) or a 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 go the hard way, we will decide along the way.
Thus, in one case, you will get a medium-wave direct-gain receiver on transistors, an FM-range superheterodyne made on a microcircuit, and a common tube sound amplifier. No one will see transistors and microcircuits, only a radio tube will catch the eye, and, demonstrating the design, I will say:
Here, they knew how to do it before, only one radio tube, and how many stations it receives! And what a sound! Just listen….
Getting Started the first part of the project.
Three-stage selective high-frequency amplifier.
Scheme.
A feature of the circuit is the presence of tunable circuits in all three high-frequency amplification stages. Here, a three-section block of a variable capacitor from an old radiola is fully used. But it still wasn’t enough for the input circuit, and therefore the broadband preselector consists of a filter, concentrated selection, 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 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 able to cut off unnecessary interference. Wired Internet, cell phone chargers, cheap voltage converters of other electronic devices completely "kill" the medium wave range with their emissions at these frequencies.
Each cascade operates in a mode that provides a stable gain due to the use of negative feedbacks, a cascode switching circuit of the second cascade, incomplete switching on of the circuits and the presence of resistors in the collectors of transistors that dampen their gain and reduce interference between them during the tuning process, as well as separate additional filters on nutrition. Experience shows that a multi-stage tunable high-frequency amplifier is prone to self-excitation, to unstable operation, and therefore all measures have been taken, which, in my opinion, ensure normal operation of the amplifier.
Structurally, each stage of the amplifier is closed by a screen, and each coil is made in a screen, and the screen for it 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 on a TDA 7050 chip, which in the article "
Immediately turned out the receiver 3 - V -1.
Adjustment.
The receiver will work immediately, but needs a little adjustment. Having tuned in to the radio station in the upper part of the range, we achieve the maximum volume with subscript capacitors, and at the bottom of the range we fix the pieces of ferrite with a compound next to the coils at the maximum reception volume.
If the receiver is unstable, prone to self-excitation, then it is necessary to increase the values of the resistors R 5; 9; 11 -13, or the value of the capacitor C13, or add such a capacitor to the following stages.
After adjusting, I measured the receiver bandwidth at three decibels. At the bottom of the range it turned out 15 kilohertz, at the top 70 kilohertz. The sensitivity from the input from an external antenna is not worse than 200 microvolts and 20 microvolts over the range, it gradually 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 the selectivity (selectivity) in the adjacent channel. The acuity of sensations left for field tests. 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, over 100 km.
After all, the spacing between them is only 26 kHz. The first radio station listens perfectly, there are no gaps in the neighboring station. When listening to the second radio station - a score of four, if you listen, you can hear the passages from the first. This is the most annoying place in the entire receiver.
Radio Liberty is confidently received with a transmitter power of 20 kW, located more than 130 km from the place. By evening, the range comes to life, radio stations from Ukraine and Belarus are received.
Tuning on radio stations is qualitatively different from superheterodyne receivers, since there is no noise between stations. If the included 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 soulful sound, with memories of childhood and youth.
To be continued, we still have to assemble a tube amplifier.
Some of the photos showing the manufacturing process are located at the end of the article.
"Competition between receivers - veterans"
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Addition. September 2012
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| Magnetic antenna on a ferrite rod. |
Antique radios were once very popular. Today, decorating a room more and more often cannot do without these items. It turns out that they can decorate a modern home. How? Judge for yourself. This is our story today.
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Decide which ones you are interested in. And once you make a purchase, you will understand their significance in our history and culture.
Material courtesy of Mary Jo Bowling.