Western collections of lamp kv regenerative receivers. Single-tube regenerator, two-tube superheterodyne…
Coils are wound with wire in any insulation. The wire diameter of the coils L1 and L2 is from 0.1 to 0.2 mm. The wire diameter for the L3 coil is from 0.1 to 0.15 mm. The winding is carried out "in bulk", that is, without observing any order of the arrangement of the turns.
The beginning and end of each coil is passed through small holes pierced in cardboard cheeks. After winding the coils, it is desirable to impregnate them with hot paraffin; this will increase the strength of the windings and further protect them from moisture.
When you go camping, check with the nearest radio station on what wave the local radio station operates on, and wind the receiver coils taking into account the following data.
To receive radio stations with a wavelength of 1,800 to 1,300 m, coils L1 and L2 are wound with 190 turns of wire. To receive waves from 1,300 to 1,000 m - 150 turns each; for waves from 500 to 200 m - 75 turns each. In all cases, 50 turns are wound on the L3 coil. You only need to wind the wire in one direction. When the wire is wound on the coil, it is fixed on the top side of the mounting plate and connected to the circuit. In this case, the end of K1 from the upper coil is passed through the hole / in the panel and is attached to pin 2 of the first lamp; the end K2 of the upper coil is connected to the end K3 of the lower coil. The connection must be made with a wire about 100 mm long. The end K1 of the lower coil through hole 2 is connected to pin 3 of the first lamp. The end K5 of the middle coil is soldered through hole 4 to pin 2 of the second lamp. The end of K6 is soldered through hole 3 to the right bracket of the phone.
To power the receiver, you need to have 7 batteries from a flashlight. Five of them are connected to each other in series, that is, the plus of one battery is connected to the minus of the second, the plus of the second to the minus of the third, etc. and are connected to the brackets plus the anode and minus the anode. With the other two batteries, they do this: the zinc cups of all the elements are connected together and connected to the minus glow bracket, and the carbon rods connected together are connected to the plus glow bracket through the switch. Headphones are attached to the “phone” brackets. If piezo headphones are used, then resistance from 10 thousand to 20 thousand ohms is connected to their ends (in parallel).
The receiver is assembled. You just have to fix it. You insert the lamps, attach the antenna (a piece of wire 8-10 m, thrown on a tree) and make a ground (drive an iron pin into the ground). Now temporarily close the ends of the coil feedback K5 and K6 and, turning on the heat, move the upper coil along the frame until you hear a transmission. If the receiver cannot be adjusted, remove the top coil from the frame and put it on the other side. Set up again. If in this case you do not hear the transmission, connect a capacitor of constant capacitance in parallel with the circuit to the ends of K1 and K2, choosing its value from 100 to 500 mmF. When connecting capacitors, you need to re-configure.
By connecting capacitors of various capacities, you can tune the receiver to any of the radio stations that is well heard in the area. Having achieved this, open the ends of the feedback coil: the volume of reception should increase. By moving the middle coil along the frame, achieve the highest volume. If turning on the feedback coil does not increase the volume, swap (solder) the ends of K5 and K6 of the feedback coil. And if a sharp whistle appears when you turn on the feedback coil, reduce the number of turns in this coil. After the final adjustment, fix the coils with a drop of glue and mount the receiver in a plywood box.
From the magazine "Young Technician" for May 1957
A diagram of a homemade regenerative receiver on a low-voltage battery-powered lamp. The radio receiver uses only one radio tube, supplemented by a minimum number of electronic components. Depending on the parameters of the coils, the radio receiver can operate in the MW, LW and HF bands.
Rice. 1. Experimental circuit diagram lamp receiver.
The anode voltage is safe for life and can vary between 20-50V. To provide anode voltage, several KRONA batteries connected in series can be used.
Triodes, powerful tetrodes, pentodes, etc. can also be used as a radio tube (in the G-807 scheme). For example, in this scheme will work: 6P9, 6P3S, 6P7S, G-807, G-811 and even GU-50.
Rice. 2. Radio tube G-807.
Rice. 3. The pinout of the G-807 lamp.
As phones, you need to use high-impedance headphones such as TON-2, or connect a TVZ transformer instead, and low-impedance headphones or a dynamic head are already connected to it.
Rice. 4. Radio tube 6P7S.
Rice. 5. The pinout of the 6P7S radio tube.
We wind coils L1 and L2 on one common frame. The number of turns is selected based on the desired received range. For example, for one of the HF subranges (40-80m), the L1 communication coil will contain 3 turns with a 0.5 mm wire, and the L2 loop coil will contain about 12 turns with a 0.8-1 mm wire, we make a tap from approximately 3-4th turn from above. We wind the coils on a common frame with a diameter of 40-45mm, the distance between the coils is 3-4mm.
For those who love a beautiful warm lamp glow: you can add a blue LED to the backlight of a glass bulb, as a result you can get a very beautiful glow in combination with the glow of the lamp itself.
Rice. 6. An example of the glow of a 6P7S lamp with a blue LED backlight.
Good luck with your experiment!
The sound, similar to the clinking of wine glasses and glasses, coming from a box of radio tubes, was reminiscent of preparations for a celebration. Here they are, similar to Christmas decorations, 6Zh5P radio tubes of the 60s .... Let's skip the memories. Return to the old preservation of radio components was prompted by viewing the comments on the post
"Detector and direct amplification receivers of the VHF (FM) range" ,
including a circuit on radio tubes and the design of a receiver for this range. Thus, I decided to supplement the article with the construction tube regenerative receiver of the VHF range (87.5 - 108 MHz).
Retro fiction, such direct amplification receivers, at such frequencies, and even on a lamp, were not made on an industrial scale! Time to go back in time and build a blueprint for the future.
0 – V - 1, a detector on a lamp and an amplifier for a telephone or speaker.
In my youth, I assembled an amateur radio station in the 28 - 29.7 MHz range on 6Zh5P, where a receiver with a regenerative detector was used. I remember the design turned out great.
The desire to fly into the past was so strong that I just decided to make a layout, and only then, in the future, arrange everything properly, and therefore I apologize for that negligence in the assembly. It was very interesting to find out how all this will work on the frequencies of the FM band (87.5 - 108 MHz).
From everything that was at hand, I assembled a circuit, and it worked! Almost the entire receiver consists of one radio tube, and given that more than 40 radio stations are currently operating in the FM band, the triumph of radio reception is also invaluable!
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| Photo1. Receiver layout. |
The most difficult thing I encountered was the power supply of the radio tube. It turned out several power supplies at once. The active speaker is powered from one source (12 volts), the signal level was enough for the speaker to work. Switching power supply with a constant voltage of 6 volts (twisted the twist to this value) powered the glow. Instead of an anode one, I applied only 24 volts from two small-sized batteries connected in series, I thought it would be enough for the detector and really it was enough. In the future, there will probably be a whole topic - small-sized impulse block power supply for a small lamp structure. Where there will be no bulky network transformers. There was already a similar thread: "The power supply of a tube amplifier from computer parts."
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| Fig.1. Diagram of an FM radio receiver. |
This is so far only a test circuit, which I drew from memory from another old radio amateur reader, according to which I once assembled an amateur radio station. I never found the original circuit, so you will find inaccuracies in this sketch, but it doesn’t matter, practice has shown that the restored design is quite functional.
Let me remind you that the detector is called regenerative because it uses positive feedback (POS), which is provided by the incomplete inclusion of the circuit to the cathode of the radio tube (to one turn in relation to the ground). Feedback is called because part amplified signal from the output of the amplifier (detector) is applied back to the input of the cascade. Positive connection because the phase of the reverse signal coincides with the phase of the input, which gives an increase in gain. If desired, the tap location can be selected by changing the influence of the POS or increasing the anode voltage and thereby strengthening the POS, which will affect the increase in the transfer coefficient of the detecting stage and loudness, narrowing the bandwidth and better selectivity (selectivity), and, as a negative factor, with a deeper connection will inevitably lead to distortion, background and noise, and eventually to self-excitation of the receiver or its transformation into a high frequency generator.
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| Photo 2. Model of the receiver. |
I tune at the station with a tuning capacitor of 5 - 30 pF, and this is extremely inconvenient, since the entire range is clogged with radio stations. It’s good that not all 40 radio stations broadcast from one point and the receiver prefers to take only closely spaced transmitters, because its sensitivity is only 300 μV. To fine-tune the circuit, with a dielectric screwdriver I slightly press on the coil coil, shifting it relative to the other so as to achieve a change in inductance, which provides additional tuning to the radio station.
When I was convinced that everything was working, I took everything apart and stuffed the “guts” into the drawers of the table, but the next day I connected everything together again, I was so reluctant to part with nostalgia, tune in to the stations with a dielectric screwdriver, twitch my head to the beat of musical compositions. This state lasted for several days, and every day I tried to make the layout more perfect or complete for future use.
An attempt to power everything from the network brought the first failure. While the anode voltage was supplied from the batteries, there was no 50 Hz background, but as soon as the network transformer power supply was connected, the background appeared, however, the voltage instead of 24 now increased to 40 volts. In addition to high-capacity capacitors (470 uF), I had to add a POS regulator to the second (shielding) grid of the radio tube through the power circuits. Now the tuning is done with two knobs, since the feedback level is still changing over the range, and for the convenience of tuning, I used a board with a variable capacitor (200 pF) from previous crafts. When the feedback decreases, the background disappears. An old coil from previous crafts, of a larger diameter (mandrel diameter 1.2 cm, wire diameter 2 mm, 4 turns of wire), was also tied into the kit for the capacitor, although one turn had to be closed in order to accurately fall into the range.
Design.
In the city, the receiver well receives radio stations located within a radius of up to 10 kilometers, both on a whip antenna and a wire 0.75 meters long.
I wanted to make ULF on a lamp, but there were no lamp panels in the stores. Instead of a ready-made amplifier on a TDA 7496LK chip, designed for 12 volts, I had to put a home-made one on an MS 34119 chip and power it from a constant heating voltage.
A high-frequency amplifier (UHF) is also requested to reduce the influence of the antenna, which will make the setting more stable, improve the signal-to-noise ratio, thereby increasing the sensitivity. It would be nice to do UHF on a lamp too.
It's time to finish everything, it was only about the regenerative detector for the FM band.
And if you make replaceable coils on the connectors for this detector, then
you get an all-wave direct gain receiver for both AM and FM.
A week passed, and I decided to make the receiver mobile using a simple voltage converter on a single transistor.
Mobile power supply.
Purely by accident, I discovered that the old KT808A transistor comes to the radiator from led lamp. This is how the step-up voltage converter was born, in which the transistor is combined with a pulse transformer from the old computer block nutrition. Thus, the battery provides a 6 volt filament voltage, and the same voltage is converted to 90 volts for anode power. A loaded power supply consumes 350 mA, and a current of 450 mA passes through the incandescence of the 6Zh5P lamp. With the anode voltage converter, the lamp design turned out to be small-sized.
Now I decided to make the entire receiver a tube one and have already tested the operation of the ULF on a 6Zh1P lamp, it works normally at a low anode voltage, and its filament current is 2 times less than that of a 6Zh5P lamp.
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| Installation of a radio station at 28 MHz. |
Addition to comments.
If we slightly change the circuit in Fig. 1 by adding two or three parts, then we get a super-regenerative detector. Yes, it is characterized by "mad" sensitivity, good selectivity in the adjacent channel, which cannot be said about "excellent sound quality". So far, I have not been able to get a good dynamic range from a super-regenerative detector assembled according to the scheme of Fig. 4, although for the forties of the last century it could be considered that this receiver has excellent quality. But it is necessary to remember the history of radio reception, and therefore the next step is to assemble a super-regenerative receiver on lamps.
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| Rice. 5. Tube super-regenerative FM band receiver (87.5 - 108 MHz). |
Yes, by the way, about the story.
I have collected and continue to collect a collection of circuits of pre-war (period 1930 - 1941) super-regenerative receivers on the VHF band (43 - 75 MHz).
In the article "Tube super-regenerative FM receiver (FM)"
I repeated the currently rare 1932 superregenerator circuit. In the same article, a collection of super-regenerative circuits is collected. VHF receivers for the period 1930 - 1941.
So, back to the topic of the tube regenerative receiver. . And now it's time to move on to the radio itself. Let me remind you that I built the receiver in the image and likeness of a wonderful regen, which was proposed by Romas-LY3CU. And in my experiments I completely agree with him that it is better not to find a 6G7 lamp for this receiver. She gives very good gain, especially in the version with an antenna preamplifier also on a 6G7 triode. At the same time, the sound is very clear and pleasant. I could not bring other lamps (according to the schemes that I found and according to my own research) to the same sound quality.
So, scheme.
After the audio frequency amplifier is set up and sounds properly, it's time to move on to the radio. A regenerative receiver is a very simple radio. Its use classically involves listening to local radio stations, but our receiver is great for shortwave! The first receivers, due to the lack of sufficient parts for radio amateurs in the first half of the 20th century, and indeed often the very possibility of getting an industrially manufactured radio in a store, were made on one or two lamps. An example of such a receiver is the Morgan regenerative receiver, which, as far as I know, formed the basis of our unit. I already touched it a little, but still promised to return to it.
| Morgan Regenerative Receiver |
Let's try to figure out his device. Let me also remind you that I did not advise playing this receiver directly - without ULF.
Antenna
On the left we see the antenna connected to the circuit through parallel trimmer capacitors. Alas, I do not yet know as much about antennas as I would like, so I will not say anything about them except what I have gained from my experience. I can only say that for such receivers, the antenna is almost the most important detail. There is no antenna - nothing good can be caught most likely. The good news is that a piece of wire at least a couple of meters long will do for the antenna. And yes, this is a bad antenna, but in combination with a radio ground, it will give quite good results, maybe even allow you to pick up some amateur SSB stations. It is desirable, of course, to have an external antenna, that is, taken outside the house, especially if the house, like mine, is a reinforced concrete box. In other matters, I threw the antenna out the window and hung the wire on the balcony along the windows - it’s already working out well. Then I adapted my old fishing rod and now I throw it with a piece of wire out the window perpendicular to the house. This is not a mandatory measure, but it improves my reception, and yes, I don’t give a damn what the neighbors think of me. At least, I (unlike them) do not smoke them out the window, but simply do not play pranks, do not touch anyone, hang an antenna.
I mentioned radio grounding. It is also a must. How to do it is an individual question for everyone. In a private house, you can simply bury something large and iron in the ground in the dampest corner of the house. In an apartment building, most likely, heating pipes leading to the basement have contact with the ground. However, there are more than one hundred magical volts on my pipes, from which (if you touch other electrical equipment at the same time) you feel so much current :) , connecting ground through a small ceramic capacitor of 180 picofarads (capacity, of course, approximately). So, first, I secured my receiver from unpredictable battery voltage. Secondly, from my receiver in case of any installation errors, dangerous voltage is excluded from the battery. I will remind you that in an apartment building many people have access to central heating batteries at the same time, therefore, for their safety, in no case should they be brought to the batteries high voltage! Unfortunately, people have everything not screwed to the batteries, and therefore I get hit by a hundred volts when I wipe dust on the radiator and accidentally touch the computer case ...
Also, it is forbidden to use gas supply pipes as grounding, since electricity and gas are, you know, a dangerous mixture. Of course, for radio grounding it is forbidden to use grounding in wall outlet- it has a completely different purpose. You can try to make radio grounding through metal balcony railings. Perhaps the metal is connected to the fittings of the house and also goes underground. However, in my case, the railing did not give positive results. In fact, my first grounding was an ordinary piece of wire, as if in opposition to the antenna, simply connected to the minus of the receiver and lying on the floor - it gave poor results, but it's better than without it.
I check the performance of the resulting antenna with high-impedance headphones. I'm not sure how good this method is, but I connect the antenna to one earphone pin and the ground to the other. Headphones are, as it were, connected between the antenna and the "ground". If the contact is good, a slight noise is heard in them. And, of course, regular headphones Or the speaker will not give such results. You need headphones with more than 1000 ohms. I was lucky at one time to buy such at a flea market.
Oscillatory circuit
The antenna, as mentioned above, is connected through a tuning capacitor. Here it is used at 4-80 picofarads. A regular trimmer will do. This capacitor is needed to adjust the selectivity of the receiver, since the oscillatory circuit is connected in series to the ground farther from it. Most of all I liked the coil made by millimeter copper wire on a frame from a can of sour cream in 4 turns through a millimeter :) You can take a frame from toilet paper, you can use another small jar, but not a metal one! It is possible without a frame at all, but it will be difficult to wind. You can take the usual stranded wire. In parallel with the coil, a tuning capacitor for 10-365 picofarads is connected (one section of the capacitor from the old tube receiver). Changing the capacitance of the capacitor changes the tuning frequency of the receiver.
Gridlik
Better yet: gridleak. So it’s immediately clear that the grid is leaking :) A regen coil is a resistor-capacitor pair connected between the oscillatory circuit and the grid of the regenerator lamp. Its peculiarity is that it should be a resistor with a very high resistance (meg or more), and a capacitor with a small capacitance - tens of picofarads. You can experiment and choose your gridlik.
Regenerator lamp
The circuit uses a 6BF6 triode, which personally doesn’t tell me anything, because I don’t understand anything about imported lamps, there are several pieces from the former CMEA countries in the collection, but somehow that’s all :)
Our 6G7 is perfect for the role of this lamp - a triode-double diode in a metal cylinder with a grid placed on top. The regenerator lamp is usually planted with the cathode on the "ground". If we put something into the cathode, then we will block the lamp, since the grid will immediately turn out to be more positive than the cathode, its potential is almost equal to zero. However, if resistance is still needed in the cathode, then the entire cascade of this lamp (both the grid, and the cathode, and the capacitors in the anode, etc.) should be grounded through this cathode resistor. So we will not fence the garden. A 500-kilometer potentiometer is connected to the anode of the lamp at the middle point. This is feedback. But the option with a capacitive regulator is much better!
Feedback
Most of these receivers use variable resistors to adjust the feedback depth. Romas-LY3CU in his receiver offers to use a wonderful solution - replacing this potentiometer with a variable capacitor. This is really a great option! Adjustment immediately becomes much smoother. The feedback regulator is connected here to the feedback coil, it is due to it that the regenerator works.
Feedback coil.
Pay attention to the part indicated on the diagram "Tickler coil" - this coil is inductively coupled to the coil oscillatory circuit, which means that it should be best placed on the same frame with it, but on short distance. For this purpose, I glued a paper movable ring that can be moved along with this coil back and forth along the frame to adjust the depth of feedback. This is inconvenient and unsafe to do while the receiver is operating (anode voltage is on the coil), which is why we need a feedback regulator in the form of a resistor or capacitor. However, in my receiver, I used a rotary mechanism, as a result of which my coupling coil rotates relative to the plane of the coil of the oscillatory circuit, thereby the connection either weakens or increases, expanding the range of available frequencies for the regenerator on one coil and generally helping to carry out a rough adjustment of the regenerator.
After all, the regenerator is what the regenerator is for, that it is almost a generator :). Our task is to select the feedback in such a way that the lamp is on the verge of whistling and falling into self-excitation mode. But if it is possible to stretch this generation threshold so as to bring a lamp to it and leave it in this state, then the lamp suddenly begins to become very good amplifier, while also detecting our signal, extracting an audio frequency from it! And everything happens with the correct location of the feedback coil and the selection of the regeneration depth regulator.
A three-turn coil with a 0.3 mm thick copper wire of approximately the same diameter is suitable for the communication coil for my four-turn coil. These are not absolute criteria. Try to do different coils! It is only better to take the same diameter of the frame of both coils - this way it will be possible to achieve the maximum amplitude of using the oscillatory circuit, if necessary, bringing them close.
Important note: it's not all the same how to turn on the coils!
I just drew how to connect them, it's too difficult to explain in words. It's easy to get confused. I checked several times, everything seems to be correct. In general, the idea is that the coils are aligned so that an inductive coupling is formed between them. If the receiver is silent, it is likely that the connection of the coils is mixed up. Normally, when they move, the sound of the ether should appear. If it is not there, it is necessary to check the circuit of the oscillatory circuit and the cascade of the 6G7 lamp, if there are no breaks, a constant anode current 6G7 flows through the communication coil, the connection of the coils is most likely mixed up. You may also need to check the ULF coupling capacitor. You don’t need to dig the ULF itself, since we have already built and configured it, and now it’s a big part of the circuit :) That’s why it’s so important to follow the assembly sequence.
Air noise will appear even without connecting the antenna and grounding, although it will probably not be possible to catch anything on the receiver without them.
Head phones. Better amp!
I already wrote that there is nothing to rush and spoil your hearing with squeaks and pops in high-impedance headphones. Get yourself an amplifier. It is connected through a coupling capacitor with a capacity of around 2200 picofarads. A current-limiting resistor of 2.5 megohms is included, as you understand, so as not to burn the coils in the headphones with direct current.
Variant of the scheme that I have collected:
Let's go over the details:
R20 - anode current limiting resistor. Its resistance is from several tens to several hundred kilos. The higher it is, the less current flows through the lamp and the weaker the connection between coils L1 and L2. But the regen feature is such that the lamp coolly approaches the generation threshold when it has a relatively low voltage - 55 volts! In this circuit, it will be about 75 volts. In this mode, it also, as it seemed to me, (alas, only subjective sensations) amplifies better, and more stations are received. In general, I decided to stop at 220 kilomas in the anode, Romas has 120 - IMHO: not enough. You can lower the voltage even more, you can even shunt the lamp with a resistor to bring it to low values. The generation is pleasant, but the sensitivity drops. The coils, even brought close together, quickly stop introducing the lamp into generation. In general, put a kilo of 200.
C14, C15 - decoupling capacitors of the anode circuit. We don’t need the RF signal, and everything else, to also penetrate other tube stages, so these capacitors are placed in the region of hundreds of picofarads for RF decoupling, but C14 already filters the low frequencies, moreover, throughout the anode circuit, as you may notice.
Dr1 - A very important detail! Yes, it is possible without a throttle at all. It will work, but not at all like with a throttle. Let's talk about its purpose. It is included in the anode circuit, that is, it must pass D.C.(which is very small here, so the thickness of the wire, it would seem, is not critical - nothing will burn out, but there is a nuance!) Look at what point the throttle is: it is located between the communication coil and the communication capacitor with the ULF. Now imagine it doesn't exist. The radio frequency generated by the lamp is induced on the communication coil, and the detected sound, isolated during the so-called. grid detection by the same lamp. There is no throttle. It would seem, so what? For sound, the choice is obvious - to go through the coupling capacitor further into the sound stages. It is difficult to pass through the anode 220 kilos. And yes, this happens without a throttle. But what happens if you put a choke with a good inductance - about 10 mH? We calculate the reactance of such a choke for radio frequency. XL = 2πfL. Let our frequency of 3 million hertz be the lower limit of short waves. For her, the throttle will create a resistance of 188.4 kilomas! This resistance across the inductor will increase the amplification power of the radio waves in the receiver. The choke here is a radio frequency amplifier! At the same time, for voice frequencies, it is easy to calculate that at 100 hertz the inductor will give a resistance of only 6.28 ohms and easily pass them to the capacitor ... but ... here lies the nuance. We never take into account the resistance of the wires in the receiver, assuming they are equal to zero, but what if the wire is very long and thin? If you wind the inductor with a thin wire, then its resistance will increase, perhaps up to hundreds of ohms. This is already critical for any currents. And since they are still weak here, not amplified, the choke from a thin wire will begin to muffle the sound detected by the lamp. It's not that much, but it's noticeable. Therefore, I strongly advise you to take the postings for this throttle thicker! In general, it turns out, of course, not very economical, but we are not in mass production, but for ourselves! :) You can pamper yourself with expensive chokes :) By the way, how I wound the choke. Okay, but you can increase the inductance by introducing a core into the inductor! This is a fair observation, but ferrite cores do not like radio frequencies. I've read that they lose a lot of energy and damp in them, so I suspect that ferrite will not give such amplification as an air choke. I put a choke from a receiver with a ferrite and subjectively my air sounds better, although that one is possible, but it’s important for us to squeeze the maximum out of the radio, especially if the antenna is weak. So we wind, we shake the throttle, gentlemen!
C13 - necessarily tuning. If you are completely strained with them, then you can put a variable potentiometer instead, as in a Morgan receiver, by shunting the coil. But I strongly advise you to install a capacitor, with an air one. If there is a regular one at 365 picofarads, then you can use it, but it will become more difficult to set up the generation. You can try to connect a capacitance in series with it, according to the law, the total capacitance will become less than the smaller one: C1xC2 / (C1 + C2). . To be honest, I went back to the original version. Homemade wheezes and closes, it didn’t work out right, so I soon played enough of them. In general, find a good air variable, but not less than 100 picofarads, otherwise the adjustment band will become very small, and without an adjustable feedback coil, it will quickly leave the generation point when searching for stations and it turns out that the receiver works only in a small radio frequency band. In general, set the usual, picofarad to 300 for a start :)
Yes, how it works. Conder closes our communication coil to ground. As a result, it creates reactance for the detected frequency. Unfortunately, it will not be possible to make the capacitor open generation at a fixed position. This is due to the fact that for different frequencies it has a different bandwidth. That is why I made the feedback coil also movable, so that you can roughly tune the connection with it, and then gently adjust it with this conduit.
I do not consider myself competent to explain the process, but I understand it in such a way that the tuning KPI, like the coupling coil, is able to change the bandwidth of the detected signal. With a minimum capacity (plates extended), the connection is too weak - the receiver is silent. Further, by sliding the plates, generation opens, an AM signal appears, you can listen to ordinary HF radio stations. By continuing to push the plates, we create enough capacity to low frequencies began to drain to the "ground", the sound becomes characteristically high, then single-sideband modulation or SSB opens. My understanding of the process is that the KPI is kind of cutting the detected signal harder and harder, releasing lower frequencies as we slide the plates in. But it’s quite difficult to hear the SSB station, because we need to tweak the receiver so precisely that the SSB station clearly lies in the band that we filtered in this way, otherwise the sound is either unnaturally high, or unnaturally low, or it’s impossible to make out at all. The feedback coil works similarly, but here it is already necessary to move the coils away for an effect similar to the extension of the plates.
Coils L1 and L2. It seems that enough has already been said about them. You can make them almost anything, but the nuances are as follows. Practice has shown (here again a little audiophilia) that large coils of thick wire show the best results. I suspect, since a thick wire has less resistance, which can be critical for weak, still practically not amplified, currents. It is possible that a surface effect begins to appear on the HF, HF currents begin to be forced out to the surface of the conductor, and the larger it is, the better, again, due to the drop in resistance. In general, I recommend a millimeter wire for the loop coil and somewhere 0.3-0.5 mm for the communication coil. In it, the turns must be made less than in the main coil. Try to find out by experience. I went the route of replacement coils. I made connectors for them so that you can change them. My main coil is screwed to the terminals from the outlet, I made my own connector for communication.
C17, R21 - Gridlick. I came to the conclusion that it works better with a resistor connected to ground, although you can parallel it with a capacitor. The resistor must be at least a megohm, you can try 2, 3 megohm, for some lamps you need 10 megohm. I liked it here with 1 megohm in the grid. The lower the resistance, the greater the gain, but at the expense of bandwidth expansion. Similarly with a capacitor - more capacitance - wider band, but weaker stations are heard. I have a bad antenna, so this is critical for me.
C16 is the solution to the bandwidth problem. In fact, this is a continuation of the grid, since this conduit also provides grid leakage, the larger it is, the more it will release into the "ground", which will narrow the band and prevent neighboring stations from entering. Again, a balance needs to be found here. I settled on 56 picofarads. You can put 120, or vice versa - say, 20-30. There is another option to include a capacitor in front of C17, you can also try it out.
C18 - one section of a conventional air KPI from the receiver. The larger the capacity, the better, although this will make tuning at the station more difficult. But classically it is 10 ... 365 picofarads. Coils are designed for this.
C19 - communication with the antenna. This is any tuning capacitor for units - tens of picofarads, there are many of them in receivers. I drew the capacity very conditionally. You can replace it with a constant, for example, set picofarad 100, but it is desirable to be able to adjust to attenuate some stations. Again, this is a matter of selectivity.
Criticism of the regenerator
I tried to express my vision this receiver as much as the lack of any technical education allowed me :) I suspect there is something to correct in my presentation. However, I really like this receiver. It is easy to implement and very interesting. This is not the last article, since I did not describe the connection of the antenna preamplifier, but it is very necessary, especially with a weak antenna. However, regen has a lot of drawbacks.
You can get out of the situation by building an approximate scale manually for your interchangeable coils using a frequency generator or by the already calibrated scale of another receiver, which is called "by ear". I would still run the generator around the circuit. . And I made key marks for myself, in order to at least approximately know the frequency of listening. However, my generator is still being finalized, and there is no time to deal with the scale yet. Although its absence is a significant drawback.
We will continue to talk about the construction of this regenerative receiver. I plan to highlight my experience in building a UHF and discuss the issue of connecting an indicator. But that's all for today. Good luck to all!
E. Aisberg "Radio is very simple" (E. Aisberg, La radio? .. Mais c "est tres simple!").VC. Labutin, Radiomaster's Book, Gosenergoizdat, Moscow-Leningrad, 1961 (there are different years of publication).
After making the receiver direct conversion, which pleased with its very good work, it was decided to repeat another type of radio, namely, regenerative. The peak of popularity of tube regenerative radios fell approximately in the 30-50s of the last century, as can be judged from the many publications on this topic in the then amateur radio literature. Subsequently, regenerative radios were completely replaced by superheterodynes and safely forgotten for many decades ...
At the beginning of the 21st century, regenerators were remembered, and they began to be repeated more and more often. There have been many publications and diagrams of regenerative radio receivers both on electronic tubes as well as transistors.
For repetition, the design of S. Belenetsky was chosen. This is a shortwave transistor regenerative radio receiver:
No changes were made to the radio circuitry. Only an electronic volume control on the KP501 transistor has been added. As a terminal ULF, in order to ensure loud-speaking reception, Len-B, ready from the radio station, was used.
The final circuit of the radio receiver, indicating the actual operating modes of the transistors, is shown below:
Schematic diagram of the terminal ULF on the TBA810S chip (K174UN7):
The regenerative radio receiver operates in the range of 2.9 ... 3.7 MHz and is capable of receiving radio stations operating both with amplitude modulation (AM), and with single-sideband (SSB), as well as telegraph (CW).
This regenerative radio has the following controls:
Attenuator (variable resistor R18 470 Ohm);
Tuning to the frequency of radio stations (variable capacitor C7 6 ... 500 pF);
- regeneration level (variable resistor R1 10k);
LF gain (variable resistor R17 22k);
The trimming resistor R12 sets the required gain of the preliminary ULF on transistors VT3 and VT4.
The main nodes of the regenerative receiver are:
Regenerative cascade on transistor VT1;
Detector on transistor VT2;
Preliminary ULF on transistors VT3 and VT4;
Electronic volume control transistor VT5.
As a variable capacitor, a KPI from the Ural-auto radio receiver with a capacitance change range of 6 ... This vernier will not provide comfortable tuning to radio stations due to the small slowdown, so the receiver operating range of 2.9 ... 3.7 MHz was divided into two sub-bands - 3.6 ... 3.7 MHz and 2.9 ... 3.4 MHz. In the range of 2.9 ... 3.4 MHz, the so-called "radio hooligans" work with amplitude modulation. It will be interesting to test this regenerator in this range.
The selection of stretching capacitors C17 and C18 was carried out using the KONTUR3C program.
The calculation results are presented in the table:
C17, pF C18, pF
2.9…3.4 MHz 560 390
3.6…3.7 MHz 270 750
The inductor L1 is wound on an Amidon T 50-2 ring:
The number of turns is 35, the wire is PEL-0.5. Inductance 7.1 uH.
The regenerative receiver is assembled on printed circuit board, and on the same experimental chassis as
General view of the assembled receiver on the chassis:
Top view with some explanatory inscriptions:
Location of the main elements:
The assembly of the regenerative receiver was not particularly difficult. All transistor modes were set automatically similar to the author's description. The approach to the generation mode is quite smooth. This is clearly seen when the oscilloscope monitors the local oscillator signal at the emitter of the transistor VT1- as the resistor R1 increases the voltage on the base of VT1 smoothly, without jumps, the amplitude increases high frequency voltage from zero to the maximum value.
The first inclusion was discouraging - there was silence in the dynamics, there was not even a hint of ethereal noise. An 80m Inverted V antenna was used. As it turned out, connecting the antenna disrupted the generation of the local oscillator. Reducing the number of turns of the coupling coil from three to one solved the problem. Now, when the antenna was connected, the terrestrial noise at the output of the receiver was well heard.
I had to tinker a little with laying the operating frequency range. As mentioned above, the selection of stretching capacitors was performed using the KONTUR3C program. For the correct selection of stretching capacitances, it is necessary to correctly set the value of the input capacitance of the local oscillator + mounting capacitance. In my case, this value was about 68 pF.
This regenerative receiver was tested live on the 3.5 MHz band on June 1st, 2017. Showed decent work, the local oscillator has sufficient stability.
