Tube VHF FM receiver in retro style. The original interior design in retro style - the old radio equipment has become an accented detail and causes a kind smile Do-it-yourself antique radio receiver

DIY steampunk radio. Let's continue the theme of the second life of outdated gadgets. At one time, FM radios were popular with a simple electronic setting consisting of two "Scan" and "Reset" buttons. Such a receiver can become the basis for an interesting design of a loud-speaking receiver, very successful for use in the workplace, due to its compact size and local voice acting of the workplace. The most difficult thing in the work of a radio amateur is not always the manufacture of electronic filling, but the manufacture of a strong and successful case for placing a soldered thing. To give a second life to the receiver, an attempt was made to make the body in the steampunk style. What came out of it, see below.

How to make a steampunk hull

Please do not judge strictly - this is the first attempt. In addition to developing a stylish case for the radio, the goal was to minimize costs and use available components and materials. Moreover, the materials are easy to process.

Before starting work, we will study the controls of the receiver, which will need to be placed on the case. As mentioned above, these are two tuning buttons “Scan” - tunes into stations after each press from the last radio station to the next radio station up in the range. When tuning to the latest radio station, the return to the beginning of the range is carried out by pressing the "Reset" button. In the original receiver, the third button turns on the flashlight (it was not an LED, but a light bulb!) And is not used in this design. The volume of receiving stations is regulated by a potentiometer combined with a power switch. the sound signal goes to the headphones, of course, there is no speech in any stereo signal in such a receiver. The headphone cord is also an antenna for the radio. Controls can be bought at the store or used from old equipment. In this design, controls were purchased, the total price of two buttons, a switch, an antenna terminal and a potentiometer (30 kOhm) with a handle did not exceed 150 rubles (2013). As a loudspeaker, a sensitive loudspeaker extracted from a small-sized speaker was used. Head resistance 8 ohm.

Column - donor

Speaker

1. A piece of white polystyrene sheet measuring 200x130 mm and 1.5 mm thick was taken as the basis for the case. The sheet has markings for the controls and body bends to form the spirit of the side walls 40 mm high. Possible options for using plastic junction boxes purchased at an electrical goods store as a housing.

2. On the inside, small cuts are made along the marking of the wall bend, for example, with the sharp end of scissors or a knife, 1/4 - 1/3 of the thickness of the plastic.

3. Gas lighter evenly we warm up the entire place of the bend until the plastic softens and form the side wall. The flame should not reach the bend of 10-15 mm. this will produce the most intense heating. We do the same operation with the second wall. The resulting "P" - shaped body must be supported by all ends of the side walls on the surface.

Hull details

Workpiece marking

4. After the body is made, holes can be made. The sound from the speaker will be transmitted towards the listener through the bell. A siphon was taken as a socket to remove water from the floor (made in Spain :)). The hole for the speaker - the bell can be drilled with a thin drill, and then trimmed with a knife.

5. The front and back walls are also cut out with tailor's scissors from sheet polystyrene and glued with glue for gluing plastic models.

6. We process the gluing seams with a thin emery cloth to align the edges.

7. The drain is made of incomprehensible plastic and it was not possible to glue it. To maintain the style, the included threaded collar was used, which was attached to the body with hot glue from the inside. At the same time, we fix the loudspeaker with hot glue.

Holes in the body

Clamp fixed

receiver housing

8. In the resulting case, install the controls. From the old receiver we use the battery compartment, from which we remove unnecessary plastic.

9. Carefully remove the potentiometer from the receiver board with a soldering iron and solder the extension wires for:

- setting buttons;

- loudspeaker;

- volume control potentiometer;

- power switch;

- receiver power supply, minus to the switch, plus to the battery compartment;

- antennas, it is better to wind the antenna wire on a pencil and place it slightly stretched in the receiver case, so you may not need to connect an external antenna.

10. We solder the conductors to the controls. Insert batteries. We check the operation of the receiver, if we didn’t make a mistake anywhere, then the electronics will immediately work.

11. We fix the board, battery compartment and antenna inside the case with hot glue. Look at the photo. Cut out the bottom cover from corrugated cardboard. The retro radio is ready.

Board connected

Receiver Basement

Within the city, the radio receiver receives almost all stations, in the suburbs the number of received stations may decrease and you will need to connect an external antenna, a piece of wire up to a meter long should be enough. Do not expect high volume from the receiver, if you need to increase the volume, then you need to build in an amplifier. An example of an amplifier is given.

The basis for the steampunk design is ready.

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-band 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 itself is made in the form of a coil, to emphasize the retro style.

Sketch of the coil in the screen.

Inside such a screen there is an industrial-made choke on a ferrite core, with an inductance of 200 microhenry. At the chokes, I unwound half the turns, made a tap and then restored the coil. The magnetic antenna itself currently needs to be improved, as it has a large unevenness in the range (about 10 decibels). With it, the receiver works better than with a conventional band-pass filter on discrete elements and an external antenna.

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 is in the article “High-impedance telephone for a detector receiver”.
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.
" "
.

Addition. September 2012

Magnetic antenna on a ferrite rod.

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 (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

Recently, there has been a great interest in antique and retro radio equipment. The items of the collections are both copies of retro radio equipment of the 40-60s, and real antique devices of the 10-30s of the last century. In addition to collecting original items, there is a growing interest in collecting and making so-called replicas. This is a very interesting direction of amateur radio creativity, but first let's explain the meaning of this term.

There are three concepts: original, copy and replica of an antique item. The term "original" needs no description. A copy is a modern repetition of some antique product, down to the smallest details, materials used, design solutions, etc. A replica is a modern product made in the style of products of those years and, if possible, with approximate design solutions. Accordingly, the closer the replica is to the original products in terms of style and detail, the more valuable it is.

Now on sale there are many so-called radio souvenirs, mostly made in China, decorated in the form of retro and even antique radio equipment. Unfortunately, upon closer inspection, it is clear that its value is low. Plastic handles, painted plastic, body material - MDF pasted over with a film. All this speaks of a very low-grade product. As for their "stuffing", it, as a rule, is a printed circuit board with modern integrated elements. The internal installation of such products in terms of quality also leaves much to be desired. The only "advantage" of these products is their low price. Therefore, they may be of interest only to those who, without going into technical subtleties or simply not understanding them, want to have an inexpensive "cool thing" on their desk in their office.

As an alternative, I want to present a receiver design that fully meets the requirements of an interesting and high-quality replica. This is a super-regenerative tube VHF FM receiver (Fig. 1), operating in the frequency range of 87 ... 108 MHz. It is assembled on radio tubes of the octal series, since it is not possible to use lamps with a pin base, older and suitable in style, in this design due to the high operating frequency of the receiver.

Rice. 1. Super-regenerative tube VHF FM receiver

Bronze terminals, control knobs and brass nameplates are an exact copy of those used in products of the 20s of the last century. Some elements of fittings and design are original. All radio tubes of the receiver are open, except for the screens. All inscriptions are made in German. The body of the receiver is made of solid beech. Installation, with the exception of some high-frequency nodes, is also made in a style as close as possible to the original of those years.
The front panel of the receiver has a power switch (ein / aus), a frequency setting knob (Freq. Einst.), a frequency scale with an arrow tuning indicator. The volume control (Lautst.) - on the right and the sensitivity control (Empf.) - on the left are displayed on the top panel. Also on the top panel there is a pointer voltmeter, the backlight of the scale of which is an indication of the power on of the receiver. On the left side of the case there are terminals for connecting the antenna (Antenne), and on the right side there are terminals for connecting an external classical or horn loudspeaker (Lautsprecher).

I want to note right away that the further description of the receiver device, despite the presence of drawings of all the details, is for informational purposes, since the repetition of such a design is available to experienced radio amateurs, and also implies the presence of certain wood and metalworking equipment. In addition, not all elements are standard and purchased. As a result, some installation dimensions may differ from those given in the drawings, as they depend on the elements that will be available. For those who want to repeat this one-to-one receiver and who need more detailed information about the design of certain parts, assembly and installation, drawings are offered, as well as the opportunity to ask a question directly to the author.

The receiver circuit is shown in fig. 2. Antenna input is designed to connect a balanced VHF antenna drop cable. The output is designed to connect a loudspeaker with a resistance of 4-8 ohms. The receiver is assembled according to the 1-V-2 scheme and contains a UHF on a VL1 pentode, a super-regenerative detector and a preliminary UHF on a VL3 double triode, a final UHF on a VL6 pentode and a power supply on a T1 transformer with a rectifier on a VL2 kenotron. The receiver is powered by 230 V.

Rice. 2. Receiver circuit

UHF is a range amplifier with a diversity tuning of the circuits. Its tasks are to amplify the high-frequency oscillations coming from the antenna, and to prevent the penetration into it and radiation into the air of its own high-frequency oscillations of the super-regenerative detector. UHF is assembled on a high-frequency pentode 6AC7 (analogue - 6Zh4). The connection of the antenna with the input circuit L2C1 is carried out using the coupling coil L1. The input impedance of the cascade is 300 ohms. The input circuit in the grid circuit of the VL1 lamp is tuned to a frequency of 90 MHz. The setting is carried out by selecting the capacitor C1. The L3C4 circuit in the anode circuit of the VL1 lamp is tuned to a frequency of 105 MHz. The setting is carried out by selecting the capacitor C4. With this configuration of the circuits, the maximum UHF gain is about 15 dB, and the frequency response unevenness in the frequency range of 87 ... 108 MHz is about 6 dB. Communication with the subsequent cascade (superregenerative detector) is carried out using the L4 coupling coil. Using a variable resistor R3, you can change the voltage on the screen grid of the VL1 lamp from 150 to 20 V and thereby change the UHF transmission coefficient from 15 to -20 dB. Resistor R1 serves to automatically generate a bias voltage (2 V). Capacitor C2 shunting resistor R1 eliminates AC feedback. Capacitors C3, C5 and C6 - blocking. The voltages at the terminals of the VL1 lamp are indicated for the upper position of the resistor R3 engine according to the diagram.

Super Regenerative Detector assembled on the left half of the double triode VL3 6SN7 (analogue - 6H8C). The super-regenerator circuit is formed by an inductor L7 and capacitors C10 and C11. The variable capacitor C10 serves to tune the circuit in the range of 87 ... 108 MHz, and the capacitor C11 - to "lay" the boundaries of this range. In the grid circuit of the triode of the superregenerative detector, the so-called "gridlick" is included, formed by the capacitor C12 and the resistor R6. With a selection of capacitor C12, a damping frequency of about 40 kHz is set. The connection of the super-regenerator circuit with UHF is carried out using the L5 coupling coil. The supply voltage of the anode circuit of the super-regenerator is supplied to the output of the loop coil L7. Inductor L8 - superregenerator load at high frequency, inductor L6 - at low frequency. Resistor R7 together with capacitors C7 and C13 form a filter in the power circuit, capacitors C8, C14, C15 are blocking. The AF signal through the capacitor C17 and the low-pass filter R11C20 with a cutoff frequency of 10 kHz is fed to the input of the preliminary ultrasonic frequency converter.

Preliminary ultrasound assembled on the right (according to the scheme) half of the triode VL3. The cathode circuit includes a resistor R9 for automatically generating a bias voltage (2.2 V) on the grid and a choke L10, which reduces the gain at frequencies above 10 kHz and serves to prevent the penetration of superregenerator quenching pulses into the final ultrasonic frequency converter. From the anode of the right triode VL3, through the coupling capacitor C16, the AF signal is fed to the variable resistor R13, which acts as a volume control.

The power supply provides power to all components of the receiver: an alternating voltage of 6.3 V - to power the incandescent lamps, a constant unstabilized voltage of 250 V - to power the anode circuits of the UHF and the final ultrasonic frequency converter. The rectifier is assembled according to a full-wave circuit on a VL2 5V4G kenotron (analog - 5Ts4S). The rectified voltage ripple is smoothed out by the C9L9C18 filter. The supply voltage of the super-regenerator and the preliminary ultrasonic frequency converter is stabilized by a parametric stabilizer on the resistor R14 and gas-discharge zener diodes VL4 and VL5 VR105 (analogue - SG-3S). The R12C19 RC filter additionally suppresses voltage ripple and zener diode noise.

Construction and installation. UHF elements are mounted on the main chassis of the receiver around the lamp panel. To prevent self-excitation of the cascade, the grid and anode circuits are separated by a brass screen. Communication coils and loop coils are frameless and mounted on textolite mounting racks (Fig. 3 and Fig. 4). Coils L1 and L4 are wound with a silver-plated wire with a diameter of 2 mm on a mandrel with a diameter of 12 mm with a pitch of 3 mm.

Rice. 3. Communication coils and contour coils are frameless, mounted on textolite mounting racks

Rice. 4. Communication coils and contour coils are frameless, mounted on textolite mounting racks

L1 has 6 turns with a tap in the middle and L4 has 3 turns. Loop coils L2 (6 turns) and L3 (7 turns) are wound with a silver-plated wire with a diameter of 1.2 mm on a mandrel with a diameter of 5.5 mm, the winding pitch is 1.5 mm. Loop coils are located inside the coupling coils.

The screen grid voltage of the VL1 lamp is controlled by a pointer voltmeter located on the top panel of the receiver. The voltmeter is implemented on a milliammeter with a total deviation current of 2.5 mA and an additional resistor R5. Subminiature scale backlight lamps EL1 and EL2 (CMH6.3-20-2) are placed inside the milliammeter case.

Rice. Fig. 5. Elements of the super-regenerative detector and preliminary USCH, mounted in a separate shielded block

The elements of the super-regenerative detector and the preliminary UZCH are mounted in a separate shielded block (Fig. 5) using standard mounting racks (SM-10-3). The variable capacitor C10 (1KPVM-2) is fixed on the block wall with glue and a textolite sleeve. Capacitors C7, C8, C14 and C15 are pass-through series KTP. The inductor L6 is connected through the capacitors C7 and C8. The supply voltage to the shielded unit is supplied through the capacitor C15, and the filament voltage is supplied through the capacitor C14. Oxide capacitor C19 - K50-7, inductor L8 - DPM2.4. The inductor L6 is self-made, it is wound in two sections on a Sh14x20 magnetic circuit and contains 2x8000 turns of PETV-2 0.06 wire. Since the choke is sensitive to electromagnetic pickups (in particular, from the elements of the power supply), it is mounted on a steel plate above the UHF (Fig. 6) and closed with a steel screen. It is connected with shielded wires. The braid is connected to the body of the super-regenerator unit. For the manufacture of the L10 inductor, an SB-12a armored magnetic circuit with a permeability of 1000 was used, a winding was wound on its frame - 180 turns of PELSHO 0.06 wire. Coils L5 and L7 are wound with a silver-plated wire with a diameter of 0.5 mm with a pitch of 1.5 mm, on a ribbed ceramic frame with a diameter of 10 mm, which is glued using a textolite sleeve into the hole of the lamp panel. The inductor L7 contains 6 turns with a tap from 3.5 turns, counting from the top according to the output circuit, the coupling coil L5 is 1.5 turns.

Rice. 6. Choke mounted on a steel plate above the UHF

The shielded block is attached to the main chassis of the receiver using a threaded flange. The connection of the capacitor C16 and the resistor R13 is made by a shielded wire with the shielding braid grounded near the resistor R13. The rotation of the rotor of the capacitor C10 is carried out using a textolite axis. To ensure the necessary strength and wear resistance of the splined connection of the axis and the C10 capacitor, a cut was made in the axis, into which a fiberglass plate was glued. One end of the plate is sharpened so that it fits snugly into the slot of the capacitor C10. The axle is fixed and pressed against the condenser spline by means of a spring washer laid between the bracket sleeve and the driven pulley fixed on the axle (Fig. 7).

Rice. 7. Shielded block

The vernier is assembled on two brackets fixed on the front wall of the shielded block of the super-regenerator (Fig. 8). Brackets can either be made independently, according to the attached drawings, or you can use a standard aluminum profile with minor modifications. To transmit rotation, a nylon thread with a diameter of 1.5 mm was used. You can use a "harsh" shoe thread of the same diameter. One end of the thread is attached directly to one of the pins of the driven pulley, and the other - to the other pin through the tension spring. Three turns of thread are made in the groove of the leading axis of the vernier. The driven pulley is fixed on the axis so that in the middle position of the variable capacitor C10, the end hole for the thread is located diametrically opposite to the leading axis of the vernier. Both axles are equipped with extension nozzles, fixed to them with locking screws. On the nozzle of the leading axis there is a frequency adjustment knob, and on the nozzle of the slave - a pointer scale indicator.

Rice. 8. Vernier

Most of the elements of the final ultrasonic frequency converter are mounted on the terminals of the lamp panel and mounting racks. The output transformer T2 (TVZ-19) is installed on an additional chassis and is oriented at an angle of 90 ° with respect to the magnetic circuit of the inductor L9 of the power supply. The connection of the control grid of the VL6 lamp with the engine of the resistor R13 is made with a shielded wire with grounding of the shielding braid near this resistor. Oxide capacitor C21 - K50-7.

The power supply unit (except for elements L9, R12 and R14, which are mounted on an additional chassis) is mounted on the main chassis of the receiver. Choke L9 unified - D31-5-0.14, capacitor C9 - MBGO-2 with flanges for mounting, oxide capacitors C18, C19 - K50-7. For the manufacture of the T1 transformer with an overall power of 60 V-A, a Sh20x40 magnetic circuit was used. The transformer is equipped with stamped metal covers. On the top cover there is a panel of the VL2 kenotron together with a brass decorative nozzle (Fig. 9). A mounting block is installed on the bottom cover, where the necessary outputs of the transformer windings and the output of the cathode of the kenotron are brought out. The power transformer is attached to the main chassis with studs that tighten its magnetic circuit. The stud nuts are four threaded posts, on which the additional chassis is fixed (Fig. 10).

Rice. 9. Kenotron panel VL2 with brass decorative cap

Rice. 10. Additional chassis

The entire installation of the receiver (Fig. 11) is carried out with a single-core copper wire with a diameter of 1.5 mm, placed in a lacquered cloth tube of various colors. Its ends are fixed with a nylon thread or pieces of a heat-shrinkable tube. The assembly wires assembled in bundles are interconnected with copper brackets.

Rice. 11. Mounted receiver

Before installation, the transformer T1 and capacitors C13, C18, C19 and C21 are painted with Hammerite hammer black paint from an airbrush. The power transformer is painted in a contracted state. When painting capacitors, it is necessary to protect the lower part of their metal case, which is adjacent to the chassis. To do this, before painting, the capacitors can, for example, be fixed on a thin sheet of plywood, cardboard or other suitable material. At the power transformer, before painting, it is necessary to remove the decorative brass nozzle and protect the kenotron panel from paint with masking tape.

The body of the receiver is wooden and made of solid beech. The side walls are connected with a tenon joint with a pitch of 5 mm. An understatement was made in the front of the case to accommodate the front panel. Rectangular holes are made in the side and rear walls of the case. The outer edges of the holes are processed with an edge radius cutter. On the inner edges of the holes, there are understatements for fastening the panels. Panels with contact input and output terminals are fixed in the side openings of the case, and a decorative grille is in the back. The upper and lower parts of the body are also made of solid beech and finished with edge cutters. All wooden parts are stained with a mocha stain, primed and varnished with professional paints and varnishes (LKM) from Votteler with intermediate grinding and polishing according to the instructions attached to these paintwork materials.

The front panel is painted with "Hammerite black smooth" paint using a technology that gives a large, pronounced shagreen (large droplet spray onto a heated surface). The front panel is fixed on the receiver body with brass self-tapping screws of appropriate sizes with a semicircular head and a slot. Similar brass fasteners are available in some hardware stores. All nameplates are custom made and CNC laser engraved on 0.5mm thick brass plates. They are mounted on the front panel with M2 screws, and on a wooden panel - with brass self-tapping screws.

After assembling the receiver and checking the installation for possible errors, you can proceed with the adjustment. To do this, you will need a high-frequency oscilloscope with an upper cut-off frequency of at least 100 MHz, a capacitor capacitance meter (from 1 pF) and, ideally, a spectrum analyzer with a maximum frequency of at least 110 MHz and a swept frequency generator (SFS) output. If the spectrum analyzer has a GKCh output, it is possible to observe the frequency response of the objects under study. A similar instrument is, for example, the SK4-59 analyzer. If this is not available, an RF generator with the appropriate frequency range will be required.

A properly assembled receiver starts working immediately, but requires adjustment. First check the power supply. To do this, the VL1, VL3 and VL6 lamps are removed from the panels. Then a load resistor with a resistance of 6.8 kOhm and a power of at least 10 W is connected in parallel with the capacitor C18. After turning on the power supply and warming up the kenotron VL2, the gas-discharge zener diodes VL4 and VL5 should light up. Next, measure the voltage across the capacitor C18. With an unloaded filament winding, it should be slightly higher than indicated on the diagram - about 260 V. At the anode of the zener diode VL4, the voltage should be about 210 V. The alternating voltage of the glow tubes VL1, VL3 and VL6 (in their absence) is about 7 V. If all of the above above the voltage value is normal, the test of the power supply can be considered complete.

Unsolder the load resistor and install the VL1, VL3 and VL6 lamps in their places. The sensitivity control slider (resistor R3 is set to the upper position according to the diagram, and the volume control (resistor R13) is set to the minimum volume position. A dynamic head with a resistance of 4 ... 8 ohms is connected to the output (terminals XT3, XT4). After turning on the receiver and warming up all radio tubes check the voltage at their electrodes in accordance with those indicated in the diagram.When the volume is increased by turning the resistor R13, the characteristic high-frequency noise of the super-regenerator should be heard in the loudspeaker.Touching the antenna terminals should be accompanied by an increase in noise, which indicates the correct operation of all stages of the receiver.

Adjustment begins with a super-regenerative detector. To do this, the screen is removed from the VL3 lamp and a communication coil is wound around its cylinder - two turns of a thin insulated mounting wire. Then install the screen back, releasing the ends of the wire through the top hole of the screen and connecting the oscilloscope probe to them. With the correct operation of the superregenerator, characteristic flashes of high-frequency oscillations will be visible on the oscilloscope screen (Fig. 12). By selecting capacitor C12, it is necessary to achieve a flash repetition rate of about 40 kHz. When tuning the receiver over the entire range, the burst repetition rate should not change noticeably. Then the tuning range of the super-regenerator is checked, which determines the tuning range of the receiver, and, if necessary, it is corrected. To do this, instead of an oscilloscope, a spectrum analyzer is connected to the ends of the coupling winding. A selection of capacitor C11 lays the boundaries of the range - 87 and 108 MHz. If they are very different from those indicated above, it is necessary to slightly change the inductance of the coil L7. At this point, the setting of the super-regenerator can be considered complete.

Rice. 12. Oscilloscope readings

After adjusting the super-regenerator, the coupling coil is removed from the VL3 lamp bulb and proceed to the establishment of UHF. To do this, it is necessary to unsolder the wires going to the L6 choke, remove the choke and the plate on which it is fixed (see Fig. 6) from the chassis. This will open access to the UHF installation and turn off the super-regenerator cascade. Turning off the super-regenerator is necessary so that its own oscillations do not interfere with the UHF tuning. To one of the extreme and middle terminals of the inductor L1 connect the output of the spectrum analyzer GKCH (or the output of the RF generator). The input of a spectrum analyzer or an oscilloscope is connected to the coupling coil L4. It should be recalled that the connection of devices to the elements of the receiver must be made with coaxial cables of a minimum length, cut on one side for soldering. The termination ends of these cables should be as short as possible and soldered directly to the terminals of the respective elements. It is categorically not recommended to use oscilloscope probes for connecting devices, as is often done.

By selecting capacitor C1, the UHF input circuit is tuned to a frequency of 90 MHz, and the output circuit by selecting capacitor C4 is tuned to a frequency of 105 MHz. It is convenient to do this by temporarily replacing the corresponding capacitors with small-sized trimmers. If a spectrum analyzer is used, tuning is performed by observing the real frequency response on the analyzer screen (Fig. 13). If an RF generator and an oscilloscope are used, first adjust the input circuit, and then the output circuit according to the maximum signal amplitude on the oscilloscope screen. At the end of the tuning, it is necessary to carefully unsolder the tuning capacitors, measure their capacitance and select constant capacitors with the same capacitance. Then you need to re-check the frequency response of the UHF cascade. This completes the setup of the receiver. It is necessary to return it to its place and connect the L6 choke, check the operation of the receiver in the entire frequency range.

Rice. 13. Analyzer readings

The operation of the receiver is checked by connecting an antenna to the input (terminals XT1, XT2), and a loudspeaker to the output. Keep in mind that a super-regenerative detector can only receive FM signals on the slopes of its circuit's resonant curve, so there will be two settings per station.

If an authentic horn manufactured in the 20s of the last century is supposed to be used as a loudspeaker, it is connected to the output of the receiver through a step-up transformer with a voltage transformation ratio of about 10. You can do otherwise by including the horn capsule directly into the anode circuit of the VL6 lamp. This is how they were connected in receivers in the 20s and 30s. To do this, the output transformer T2 is removed and the terminals XT3 and XT4 are replaced with a 6 mm "Jack" socket. The desoldering of the socket and plug of the horn cord must be done in such a way that the anode current of the lamp, passing through the coils of the horn capsule, amplifies the magnetic field of its permanent magnet.

/ 25.03.2016 - 18:36
and why the hell to fence such a thing. take a ready-made VHF-IP2 unit from an old tube receiver. upchz from any TV set and the usual converter of the fm range on k174ps1 use any unch on lamps. assemble in the same case. quickly cheap and cheerful