">From the article by A.S. Popova
"Device and registering device
electric oscillations »

"> The content of this article in the main part was the subject of communication in the April meeting of the physical branch of our society ...

">At the beginning of this year, I played the reproduction of some experiments ... On the electrical fluctuations in order to use them at lectures, but the first attempts showed me that the phenomenon underlying these experiments is a change in the resistance of metal sawdust under the influence of electrical oscillations - quite impermanent ; To master the phenomenon, I had to try multiple combinations. As a result, I came to the device of a device that serves for objective observations of electrical oscillations suitable for both lecture purposes and to register electrical perturbations occurring in an atmosphere ...

">In 1891, Branly discovered that ... Metal powdersthey have the ability to instantly change their electric current resistance if the discharge of an electrophore machine or induction coil occurs near them ...

">Mechanical concussions are returned again with a latter condition characterized by a large resistance. The discharge action can again reduce it, and again the shaking can be obtained by the former resistance values \u200b\u200b...

">Before in total, I wished to give such a form to the device with sawdust in order to have a possible constancy of sensitivity ...

">The most successful form for significant sensitivity, with sufficient constancy, is made as follows. Inside the glass tube, on its walls, two strips of thin sheet platinum AB andCD almost long in the length of the tube (Fig. 1). One strip is removed on the outer surface from one end of the tube, the other is from the opposite end. Platinum strips are located at a distance of about 2 mm with a width of 8 mm; The inner ends of the strips in and with do not reach the plugs covering the tube so that the powder placed in it could not, having stuffing under the plug, to form non-destructive concussions of conducting threads, as it happened in some models. The length of the entire tube is sufficient at 6-8 cm with a diameter of about 1 cm ...

">The tube under its action is horizontally, so strips lie at its lower half and the metal powder completely covers them. However, the best action is obtained if the tube is filled with no more than half.

"> In all experiments, both the size and constancy of sensitivity affect the size of the grains of metallic powder and its substance. The best results are obtained by the use of iron powder ...

">The scheme (Fig. 2) shows the location of the parts of the device. The sawdust tube is suspended horizontally between the clips M and N on a light clock spring, which is bent for greater elasticity from the side of one Zigzag clamp. There is a call above the tube so that under its action he can give lightly blows with a hammer in the middle of the tube, protected from breaking the rubber ring. It is more convenient to strengthen the tube and the call on the total vertical plate. The relay can be placed as you please.

"> The device applies as follows. The current of the battery in 4-5 V is constantly circulating from the clamp p and platinum plate BUTfurther through the powder contained in the tube, to another plate b and over the winding of the electromagnet of the relay back to the battery. The strength of this current is insufficient for attracting the camera anchor, but if the AV tube is exposed to electrical oscillations, then the resistance will instantly decrease, and the current will increase by so much that the relent anchor will attract. At this moment, the chain that comes from the battery to the call, interrupted at the point C, closes, and the call will start acting, but the immediate cutting of the tube will again reduce its conductivity, and the relay will open the call chain. In my device, the resistance of sawdust after severe shaking is about 100,000 ohms, and the relay, having a resistance of about 250 ohms, attracts anchor at currents from 5 to 10 mA (adjustment limits), i.e. when the resistance of the entire circuit falls below thousands of ORD. On solitary fluctuation, the device responds with a short call; Continuously operating spiral discharges respond quite frequent, after approximately equal intervals with the following calls ...

">The device ... can serve for various lecture experiments with electrical oscillations ...

">Another use of an appliance that can give more interesting results will be its ability to mark electrical oscillations occurring in the conductor associated with the point BUTor in (in the scheme), in the case when this conductor is exposed to electromagnetic perturbations occurring in the atmosphere. To do this, there is a sufficient device protected from any other actions, to tie with the air wire, laid away from the telegraphs and phones, or with a rod of a thunder. All oscillationovergoing for a well-known limit in its intensity, can be marked with the device and even registered, since any closure of the relay contact in the diagram at the point FROMmay be powered, except the call, another electromagnetic mark. To do this, one end of its winding is connected between points C andD, and the other to the climb of the battery R, i.e., turn on the electromagnet into the chain parallel to the call ... In conclusion, I can express hope that my device, with further improvement of it, can be applied to the transmission of signals for distances using fast electrical oscillations, as soon as the source of such oscillations is found. With sufficient energy.

Wireless telegraphy, 1914

Detectors used in radio telegraphs can be divided into two classes: driven current or voltage. The detectors driven by voltage are always connected parallel to the condenser, since there is a large potential difference in the condenser's outputs, and detectors driven by a current include consistently with this condenser. Types of detectors can be subdivided further into different classes, namely:

• detectors based on poor contact, for example, marconi coherers;
• rectifying detectors, such as a Fleming lamp and a carcamic detector;
• electrolytic detectors, such as Festemden and Schlomyl detectors;
• thermoelectric detector, based on a pair of galene and graphite or other pairs;
• detector based on changing magnetic properties - Marconi magnetic detector.

Coherer

The coherer is the result of the work of different people - Hughes, Lodge, Branley, Popov and others. It consists of a small amount of metal sawdust placed between two electrodes. The first practical sample of the coherer for the radio telegraphy was created by Marconi. It consisted of a small amount of nickel sawdust and added to them a small percentage of silver sawdust, placed between silver electrodes that have bevelled ends, so the space between them, in which sawdust is placed, had a wedge-shaped form.

The purpose of the electrodes of such a form is to be able to regulate the sensitivity of the coherer. The greatest sensitivity is achieved when the elongated parts of the wedges are located below, and vice versa, if they are 180 ° to flip, then the sensitivity of the coherer will be minimal.

Electrodes and metal sawdust are placed in a hermetic glass tube, which creates a slight discharge. The contacts of the electrodes to which the wires are connected, are removed from the tube using the Hermovators ( fig. one.).

Fig. 1. Coherer Marconi.

The principle of operation of the coherer is based on the fact that if the voltage of the value is above a certain value appears at its outcomes, then the coherer resistance is quite high due to poor contact between metal sawdust and electrodes, drops sharply to a significantly lower value. Some people think that this is due to the electrostatic attraction between metal sawdust; Others believe that microscopic sparks are slipping between sawdust, which slightly weld the sawdust among themselves. However, for no reason, this did not occur, the very fact that if the coherer is exposed to the potential difference when the signal is submitted to it, its resistance drops very much, and if the coherer is connected consistently with the relay and power battery, and the contacts Relay commuting the recorder, then the presence of electrical oscillations will be fixed on paper, as the relay will close each time there is electrical oscillations. However, the coherer itself does not restore its former condition with high resistance, therefore a small electromagnetic hammer is used, which gently tips on the bottom of the coherer, shaking iron sawders, which leads to the restoration of the former high resistance and again makes the coherers sensitive to electrical fluctuations.

Fig. 2. Diagram of the Marconi receiver with a coherer.

On the Fig. 2. A diagram of the Marconi receiver with a coherer is shown. The antenna chain consists of tuning inductance and the primary winding of the resonant transformer, connected sequentially and connected to the antenna and grounding. The secondary winding of the resonant transformer consists of two parts connected in series with each other by the capacitor, which prevents the passage of DC through windings. The ends of the secondary coil windings are connected to the outputs of an alternating capacitor, which set the winding to the resonant frequency of the primary winding, and in parallel, the coherer is connected to this condenser.

The relay and power element connected in series are included in parallel to the condenser, which connects both parts of the secondary winding of the resonant transformer. The battery of the elements connected to the relay connects to the relay, and the electromagnetic hammer is connected parallel to the recorder, the electromagnetic hammer is connected, the coherer is driven to the original high-resistance state after it worked as a result of a high-frequency signal.

Due to the high self-induction of the coils of the relay, the recorder and the hammer, it is important that they, as well as the contacts of the relay and the hammer, would be drawn by high impeructive resistance to eliminate possible spurs, which can lead to a false triggering of the coherer.

The setting of various schemes and parts of the hardware described above is usually considered to be difficult, but if you specify systematically, it is quite simple to execute it. The operator must arrive as follows: First, with the help of an adjusting screw, install the hammer magnet so far from its reinforcement, as far as possible, and then adjust the handle of the hammer so that it is at a distance of about one millimeter from the coherer.

Then rotate the adjusting screw of the relay, which would be closed the circuit, and then slowly turn it in the opposite direction until the chain disks. Now pass any text using a buzzer (a buzzer is a small breaker, working on the battery and generating weak electrical fluctuations), and at the same time brindle the magnet of the hammer with its reinforcement until the blows have achieved sufficient force, so that you can It was clearly taking the signals of the ABC Morse.

If the strikes are too weak, the received signals will merge, and if the blows are too strong, then they will break the signals, that is, the dash will look like a number of points. The entire device described above, with the exception of the recorder, is enclosed in a metal box, which prevents the coherer damage to powerful signals that occur in the circuits during the transmitter operation.

Fig. 4. Coherer Lodge Muirhead.

This is a coherer, which can be used both with the phone and with a recorder, is arranged as follows: Little metal cup ( fig. four) Contains the mercury ball, on which a small drop of oil is located, forming an infinitely thin insulating film over it. Above the mercury ball is a small iron disk with a sharp edge, this disk is slowly rotated. Using the adjusting screw, the lower edge of the disk is lowered to contact with the oil of the oil on the surface of mercury, but if the pressure is not too large at the same time, then the oil damage does not occur. Sequentially with the coherer included galvanic elements and headphones or a recorder. When the electrical signal is passed through the chain as a result of a thin-fiber insulation film, the coherers turns into a conductive state and as a result of the electroplating current activates the headphones or the recorder. This type of coherers is restored and does not require shaking for it.

This detector consists of a platinum cup with a solution of dilute acid. A cup is one electrode, another electrode consists of a vollaston wire (this is a platinum wire, with a thickness of less than 0.01 mm, covered with silver), sealed in a glass tube, which is slightly immersed in the solution so that Whallaston wires turned out to be . Connecting to wires is carried out using a metal pipe in which the electrodes are installed. The detector consistently with high-resistant phones is connected to the moving contact of the potentiometer, the extreme conclusions of which are connected to the power battery. A small current that passes through the detector, polarizes it - gas is formed on the electrodes, with the result that the resistance of the detector increases. If the device is now alternating small potentials and currents from the receiving chain, then under the influence of electrical oscillations, depolarization will occur and the resistance of the electrolytic cell will fall, through the phones will be a small current audible by the operator. After completing the signal over the circuit, the battery again polarizes the cell, that is, the device is self-assessing. To adjust the cell, the small electrode is inserted into the holder and its tip is immersed in the electrolyte, the potentiometer knob is rotated until a hissing sound appears in the headphones, then the knob is rotated in the opposite direction until the noise stops. At this point, the detector has the greatest sensitivity.

This type of detector is widely used and is very sensitive and reliable. However, it was found that strong atmospheric interference temporarily reduce the sensitivity of the device, but for a while, since the coherer is self-asseded after a few seconds. Restoration can be accelerated by a short-term increase in voltage on terminals, it can be done if you twist a little potentiometer handle.

On the image figure 5. depicted electrode with Wellaston wire, and on figure 6. The method of connecting the detector to the battery and the potentiometer is shown.

Carboid detector

The carbonistic detector is very simple in the manufacture, its design consists of a small crystal of carbard, placed between two copper springs. It works due to the fact that silicon carbide has a property called one-sided conductivity. Suppose that the carbarund crystal is connected in series with a battery and a galvanometer, measuring the current flow flowing through the chain, now change the polarity of the battery connection and again measured the current. We will find that the current value in both measurements is very different, although the emf battery remains unchanged. This shows that for currents of the carburund going in one direction has very high resistance and is a practically insulator, and for currents going in the opposite direction, carburund is a relatively good conductor. Consequently, the carbarund crystal can work as a rectifier and transform oscillations or alternating current to constant. In addition to carboat, many crystals have the properties of one-sided conductivity, although less pronounced.

It was also found that with under stresses, one-sided conductivity of the crystal is greater than with others, and in practice for this, the crystal is supplied from the battery through the potentiometer. This detector is sensitive and reliable, and is widely used in the United States of America.

Fleming lamp

Fig. 7. Fleming lamp and its inclusion in the scheme.

The tubing lamp detector consists of a lamp with a carbon or tungsten filament, a metal plate is placed in the flask, isolated from the slope, and the connected with the conductor, the output of which passes through the glass wall of the lamp and is the third electrode. If the thread of incandestening is splitting by connecting to its conclusions of a suitable battery, the space between the thread and the insulated plate will have one-sided conductivity, and if now the lamp is included in the circuit in which there is an alternating current, then due to the rectifier properties of the lamp, alternating current will be converted In unidirectional current, which can be heard in the handset. The rectifier lamp is depicted on figure 7.The same figure also shows a way to turn on the lamp in the circuit.

If the contact site between two heterogeneous metals included in the closed circuit is heated, the current will appear in the circuit. For example, take a piece of bismuth and a bit of antimony, connect them between themselves and connect to their free ends with a suitable galvanometer and we will see that if the place of contact is heated to a higher temperature than the other parts of the scheme, the current will flow from bismuth in the direction of antimony, The value of the current will be proportional to the temperature difference between hot and cold compound parts. In almost any tutorial on electrical engineering there is a table showing the thermoelectric row of metals and their thermoelectric potentials or EDC per degree Celsius when used in a pair with lead. For example, suppose we have created a pair of tellur-lead and heated it at 1 degree Celsius above the cold part of the scheme, and the EMF will appear by about 500 microvolt.

It was found that some of the metal sulphides, for example, galvanit, have very substantial heat electric properties, and therefore galena is usually one of the elements of the thermocouple used as a detector for wireless telegraphs.

Fig. 8. Thermoelectric detector.

Two very effective combinations are a pair of galvanite graphite or galena tellur, and both pairs are high sensitivity. The design of such a detector is shown on figure 8.. Crystal Galenite soldered to the holder of a Wood alloy (this metal melts in boiling water), graphite can be taken from any sufficiently rigid pencil, very comfortable for sale with replaceable styling for pencils.

Press adjust with a small screw. As a current device, in the thermospace scheme, it is connected consistently with the capacitor, and in the presence of high-frequency oscillations in the chain, the thermospace is heated and the result is a small potential difference, which charges the capacitor, which is then discharged through the headphones.

With a good crystal, the detector galena works very stable, but the passage of strong atmospheric interference sometimes displays it, obviously, this detector behaves like a coherer and surface of the electrodes slightly weld together. If the contact graphite-galvanit is temporarily separated, and then return to the previous position, the sensitivity of the detector is completely restored.

Magnetic detector

The Magnetic Marconi Detector consists of an infinite tape that contains 70 threads of iron wire No. 40 (0.08 mm) covered with flush. The tape passes through two pulleys, which are driven by the clockwork, and at some point each point of the tape passes through the glass tube, on which the copper wire No. 36 (0.13 mm) is wound in silk insulation, the winding length of about two centimeters. This is the primary winding, terminals are connected to its ends. Above this winding is placed a coil with a secondary winding, wound up with the same wire, the winding resistance is 140 ohms, the winding ends are connected to the terminals to which the headphones are connected. Over coils are placed two horseshoe magnets with the eponymous poles located nearby, as shown on figure 9-1.. The principle of operation of the detector is based on the fact that electrical oscillations can affect the magnetic iron hysteresis. Figure 9-2.Perhaps it will help to figure out the principle of the detector. Suppose that a piece of soft iron from the AC transformer is subjected to magnetization of the power of H, which is first increased to the maximum, then drops to zero, further reaches a negative maximum and decreases again to zero, we will find that if on the same axis of the graph of the magnetization force , and on another axis - the density of power lines in, then the curve will take the view shown on fig. nine. Starting from scratch if the magnetizing force gradually increases to a maximum and if we observe the value of the flow density for each increment of the magnetizing force, we obtain the curve 0, 1. If the force has decreased to zero, the curve will not return back to the initial position, but will be follow in direction 1, 2, and if the iron is subjected to the action of the magnetizing reverse polarity force, then the curve will occur position 2, 3, 4, 5. Thus, it can be seen that the magnetic effect on the iron due to the hysteresis is lagging behind the magnetizing force, and that After magnetization, iron retains its magnetism for some time after the validity of the magnetization force. It is this lag and neutralize electrical oscillations passing through the primary winding.

Consider now the magnetic detector itself. Soft iron tape, passing over poles of two permanent magnets, and as each part of the tape passes in front of these poles, it is magnetized and under the action of the hourly mechanism, these magnetized parts move further. If the electrical oscillations will now pass through the primary winding, the tape hysteresis will disappear and the magnetized part of the ribbon, which left the magnet field, is demoted and the power lines will be redistributed through the second winding, which will result in current in it, and since the headphones are connected to the secondary Winding, then they will flow this current, which can be heard.

On the Figure 10. The device produced by Marconi is shown here it shows that there are two sets of coils and magnets, and the clock mechanism and movable metal tape are common to them. In case of failure of the detector on one side, it will be possible to easily switch to the other side. On the left side of the device is a clockwork key and a key to turn on or stopping, the adjusting screw on the right upstairs is designed to regulate the tension of the movable iron tape.

Fig. 10. Magnetic Marconi Detector (with lid-free) and telephone capacitor

On the Figure 11. The detector scheme is depicted and magnets are shown in the position of the greatest sensitivity, that is, with the eponymous poles to each other. Although in this position the system is very sensitive, but noise, sometimes audible in the phones, is very interfere with the reception of weak signals.

This deficiency can be overcome by placing magnets, as shown on figure 12.At the same time, magnets are located opposite poles to each other, and in addition, the edge of one of the magnets is slightly higher than the edge of another by moving the magnet from the tape, the best position is experimentally. The magnets used in this detector are brightly polished on one side, and on the other hand, they are shred. When both polished or buried side are in front, then the magnets will be turned to each other with the same poles, when one polished and one buried side are in front, the magnets will be arranged to each other with the varying poles. The practical use of this detector has proven its high reliability. It also has good sensitivity and practically does not require any departure except periodic clod. It was the magnetic detector of Marconi was installed on the sunken liner "Titanic".

Phone tubes

Phone tubes for receiving wireless messages are essentially not different from ordinary commercial. The difference is only in minor design details. As you know, the handset mainly consists of a permanent horseshoe magnet, on the poles of which the extension of soft iron is set to which coils with insulated copper wire windings are installed, these two coils are connected in series, and the ends of the windings are connected to the terminals. Immediately in front of the poles, close to them, there is a flexible disk (membrane) made of soft iron, fastened hard at the edges. On the figure 13. The design is shown visual. Two such telephone tubes, connected in series and attached to the connecting arc, form headphones (headphones). The phones are usually applied in schemes with a high-resistance detector, their effectiveness depends on amps-turns, usually their windings have much higher resistance than conventional commercial phones, the resistance of the windings can be in the range of 500 Ohm to 5 com and depends on Type of scheme in which they will be used. Since the copper wire in silk or paper insulation it would be impossible to obtain the required amount of turns in a small coil space, then the coils are wound up with a copper enameled wire that occupies a much less place.

Fig. 13. Phone tube device.

Phone tubes are recognized as one of the most sensitive devices from ever invented to determine the presence of an electric current, their sensitivity can be judged by the fact that the intermittent current of the magnitude of only a few microamper produces an easily heard sound in the tubes. The volume of the sound, however, depends not only on the current value, but also from its frequency. It was found that the handset has a maximum sensitivity at frequencies lying between 600 and 1000 Hz. This is undoubtedly due to the fact that the eigenfrequency of the membrane is about the same order, and also, perhaps, the fact that the human ear perceives the sounds lying at these frequencies are played.

At the beginning of this year, I played the reproduction of some experiments ... On the electrical fluctuations in order to use them at lectures, but the first attempts showed me that the phenomenon underlying these experiments is a change in the resistance of metal sawdust under the influence of electrical oscillations - quite impermanent ; To master the phenomenon, I had to try multiple combinations. As a result, I came to the device of a device that serves for objective observations of electrical oscillations suitable for both lecture purposes and to register electrical perturbations occurring in an atmosphere ...

In 1891, Branley discovered that ... Metal powders have the ability to instantly change their electric current resistance, if there is a discharge electroform machine or induction coil ...

Mechanical concussions are returned again with a latter condition characterized by a large resistance. The discharge action can again reduce it, and again the shaking can be obtained by the former resistance values \u200b\u200b...

First of all, I wished to give such a form to the device with sawdust in order to have a possible constancy of sensitivity ...

The most successful form for significant sensitivity, with sufficient constancy, is made as follows. Inside a glass tube, on its walls, two strips of thin leaf platinum AB and CD are glued almost entirely of the length of the tube (Fig. 1). One strip is removed to the outer surface from one end of the tube, the other - from the opposite end. Platinum strips are located at a distance of about 2 mm with a width of 8 mm; The inner ends of the strips in and with do not reach the plugs covering the tube so that the powder placed in it could not, having stuffing under the plug, to form non-destructive concussions of conducting threads, as it happened in some models. The length of the entire tube is sufficient at 6-8 cm with a diameter of about 1 cm ...

The tube under its action is horizontally, so strips lie at its lower half and the metal powder completely covers them. However, the best action is obtained if the tube is filled with no more than half.

In all experiments, both the size and constancy of sensitivity affect the size of the grains of metallic powder and its substance. The best results are obtained by the use of iron powder ...

The scheme (Fig. 2) shows the location of the parts of the device. The sawdust tube is suspended horizontally between the clips M and N on a light clock spring, which is bent for greater elasticity from the side of one Zigzag clamp. There is a call above the tube so that under its action he can give lightly blows with a hammer in the middle of the tube, protected from breaking the rubber ring. It is more convenient to strengthen the tube and the call on the total vertical plate. The relay can be placed as you please.

The device applies as follows. The current of the battery in 4-5 V is constantly circulating from the clamping p and platinum plate A, then through the powder contained in the tube, to another plate b and over the winding of the relay electromagnet back to the battery. The strength of this current is insufficient for attracting the camera anchor, but if the AV tube is exposed to electrical oscillations, then the resistance will instantly decrease, and the current will increase by so much that the relent anchor will attract. At this moment, the chain that comes from the battery to the call, interrupted at the point C, closes, and the call will start acting, but the immediate cutting of the tube will again reduce its conductivity, and the relay will open the call chain. In my device, the resistance of sawdust after strong shaking is about 100,000 ohms, and the relay, having a resistance of about 250 ohms, attracts anchor at currents from 5 to 10 mA (adjustment limits), i.e. when the resistance of the entire circuit drops below thousands. On solitary fluctuation, the device responds with a short call; Continuously operating spiral discharges respond quite frequent, after approximately equal intervals with the following calls ...

The device ... can serve for various lecture experiments with electrical oscillations ...

Another use of a device that can give more interesting results will be its ability to note electrical oscillations occurring in the conductor associated with the point A or B (in the diagram), in the case when this conductor is exposed to electromagnetic perturbations occurring in the atmosphere. To do this, there is a sufficient device protected from any other actions, to tie with the air wire, laid away from the telegraphs and phones, or with a rod of a thunder. Any oscillation that turns over the well-known limit on its intensity can be marked with the device and even registered, since any closure of the relay contact in the diagram at a point C can act but the call, another electromagnetic mark. To do this, one end of its winding is enough to connect between points C and D, and the other to the climb of the battery R, \u200b\u200bi.e., turn on the electromagnet into the chain parallel to the call ... In conclusion, I can express hope that my device, with further improvement, may To be applied to the transmission of signals at distances with fast electrical oscillations, as soon as the source of such oscillations is found with sufficient energy.

Kronstadt, December 1895