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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Crystal amplifier to the detector receiver. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur The most painful question for an amateur detectorist, if he wants to expand his radio horizons, is the question of enhancing the reception of stations already received by him and of receiving distant stations. "Traveling through the air" for a detectorist is very limited, and he usually either switches to a tube amplifier, or (the vast majority), having tried many circuits proposed in the literature and taking everything that he can give from the detector receiver, stops in his further experimental work, becoming a radio listener. Crystal amplification is the dream of every amateur detectorist, and he tries to achieve this by various combinations with two and three detectors, with "ultradetectors", etc. However, no noticeable practical results of amplification that can satisfy the radio amateur are obtained. Switching to tube amplifiers and tube receivers is, of course, a way out, but it is too expensive for an ordinary radio amateur. A crystalline amplifier operating on the principle of generation by a crystal, invented back in 1923 by an employee of the Nizhny Novgorod Radio Laboratory Comrade. O. V. Losev, abroad was quickly introduced into the environment of radio amateurs and found wide application. In particular, Losev's crystalline amplifiers were widely used in America and France, and in the latter this invention was given the name "cristadin". Soviet amateur radio was then still at a very low stage of development - the invention did not take root among us. And then they somehow forgot about it, and no further work was done to improve the kristadin. The literature is also very poor in material on cristadine. There is only one pamphlet published by the Society of Radio Friends of the RSFSR "O.V. Losev. Kristadin" and several articles in the journals "Radio Amateur". Abroad soon abandoned kristadin and switched to tube amplifiers due to the great cheapness of radio equipment there and one big drawback, kristadin - its instability in operation. However, the instability of kristadin is not an obstacle to its application in practice in our country. This shortcoming can be reduced to nothing during mass amateur radio experimental work. In our conditions, kristadin should find wide application. Recently, a designer has taken up the issue of generating detectors. Gribsky, who published an article on this issue in the Leningrad Worker magazine, Nos. 1 and 2, 1928, with an analysis of the fundamentals of detector generation and a number of practical proposals and schemes for experimentation. Lovers interested in kristadins can recommend Losev's pamphlet and Gribsky's article. For my part, based on my experimental work with kristadine and on the above literature, I will try to give a brief description of the simplest arrangement of a crystal amplifier for any detector receiver. The circuit diagram of such an amplifier is extremely simple (Fig. 1), its installation is easy, and the cost of parts is very small.
The amplifier is included in the antenna in front of the receiver; the ground remains attached to the receiver (seen in the figure). Installation can be done in a separate box. Then you can easily turn on the amplifier and take it both without it and with it. You can also mount it in the same box with the detector receiver, then you only need to add two switches to turn on: 1) in the antenna - only the detector receiver and 2) the receiver, in series with the amplifier. The circuit will then change as shown in Fig. 2. These circuits require a 12 volt battery consisting of 3 flashlight batteries. P-potentiometer in 500-600 ohms. R-resistance of the order of 1000-1500 ohms and self-induction. For this purpose, you can take one coil from paired telephone coils of 2100 ohms. One coil will have 1050 ohms. Of course, it is best to put here a second 500-600 ohm potentiometer with a series connection of a honeycomb coil with a resistance of 500-600 ohms, wound from 0,1 mm wire. Then the resistance will be variable, and voltage adjustment is facilitated. This option already significantly complicates the manufacture of the amplifier and increases its cost. Therefore, for starters, you can still limit yourself to a telephone coil of 1050 ohms of resistance. The P-1 switch is used to open the 4 volt battery after the amplifier has finished working. In addition, at the end of the amplifier operation, the regulating detector spring must also be raised in order to prevent the entire 12 volt battery from being discharged. Switches P-2 and P-3 in fig. 2 serve, as already mentioned above, to turn the amplifier on and off.
The most basic and critical part in the amplifier is the generating detector device. For a beginner, it can be recommended to take a crystal-zincite and a spring-steel as a generating pair. Zincite must be of good quality. It is best to melt zincite in a voltaic arc, then its generating qualities increase. However, not everyone has the opportunity to remelt, and, of course, zincite can be used without remelting. Remelting can be done on the voltaic arc of a movie camera, but at a minimum current. Zincite is placed on a carbon plate (Fig. 3) and covered with manganese peroxide (to prevent spraying at high temperature). Between the crystal and the second carbon electrode, a voltaic arc arises when the electrodes are appropriately approached, which melts the zincite.
Melting continues until the zincite turns into an oval beetle, which will take 15-20 seconds. The melt is observed through smoked or dark red glass. After melting, the zincite is cleaned from the black crust and splits, the crystal is fixed in the detector cup with a fresh break outward. The spring is made of steel 0,2 mm thick and consists of 2,5 turns (turn diameter 7-8 mm). It is best to install the anti-shake detector in a special machine recommended by Losev (Fig. 4).
Experimenters can combine a wide variety of schemes. I have personally tried several schemes, and the schemes of fig. 5 and 6.
Here I received audibility amplification by 5-6-7 times against reception without an amplifier. I received the following stations with kristadine in Leningrad: Moscow - Comintern, Moscow im. Popov. Kharkov - 4-kilowatt, Kharkov-powerful MGPS, Koenigswusterhausen, Koenigsberg, Langeborg, Vienna, Warsaw. Stockholm, Motala, Halundborg, Kattowitz, Krakow, Riga, Reval, Daventry, and, in addition, G, many unidentified foreign stations, moreover, the Comintern, Koenigswusterhausen, Motala and Popov's Moscow were accepted by me, though quietly, on the Record loudspeaker. Below is a table of generating pairs compiled by the designer Gribsky and borrowed by me from his article.
Oscillations are very unstable and are obtained only with certain grades of ferro-silicon, voltage 15-20 volts. This table does not exhaust the possible combinations of pairs. Radio amateurs have a wide opportunity to empirically look for pairs that are more stable in operation. Author: V.Kerstens
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