Radioelektronik (Radioelectronics) 1990/12
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Radioelectronics, December 1990, volume XLI (139)
FROM THE COUNTRY AND FROM THE WORLD (cover page 2)
- PHILIPS FSB260 and FSB290 hi-fi sets.
These new, uniform-looking audio sets (photo shown on cover) are intended for a wide range of middle-income buyers. Both types of sets are equipped with remote control systems, have identical turntables and CDs, but some differences exist in other parts of the sets.
- Handy, amateur mixer - tape recorder.
The Japanese company Fostex offers a new mixer - X-15-II cassette deck. The device has external dimensions of 75 x 290 x 195 mm (with a plug-in battery: 75 x 290 x 195 mm) and a weight of 2.9 kg (with battery). A standard C-60 or C-90 cassette is used to make a 4-track recording from the four inputs of the device.
- The easiest installation of optical fibers.
Early in the development of fiber optics, installing fiber optics was something of a "higher school of gas cooking" - potentially simple, but required special tools and staff preparation. Today, when installing fiber optics in the home and in the car, it had to be kept to a minimum. This is the purpose of the twisted fiber optic connector.
- Telephones for the cellular network.
The cellular telephone network in developed countries has been a reality for several years, there is also hope that as a result of giving up the state monopoly, it will appear in our country, at least in the largest urban agglomerations.
- Cooperation in microprocessors.
Two European "greats" - Siemens and SGS-Thomson - cooperate in the development, production and sale of 8 and 16 - bit microprocessors. The family of 16-bit microprocessors developed by Siemens is already beginning to appear on the market (the first commercial chip is the 80C116) and, as it turned out, it surpasses everything that was previously available in this class of chips..
ELECTROACOUSTICS - "Duetto-Stereolith" SPEAKER SYSTEM (2)
The company REVOX, known for its high quality products, offers a stereo loudspeaker system operating in accordance with a new concept. As it is easy to reproduce and gives interesting sound effects, it is worth getting to know it better.
The classic way of stereo reproduction requires the use of two loudspeakers separated by a distance, the so-called base. The optimal stereo listening position is in front of the loudspeakers, symmetrically to them. It has long been noticed that when using loudspeakers with a wide angle of sound or omnidirectional radiating units, the position of the listener in relation to the loudspeakers is less critical, but the stereo image of the sound becomes less accurate, especially in terms of the location of the apparent sound sources.
The Swiss acoustician - Walter Schupbach - proposed a solution consisting in placing the speakers of both channels in one housing in such a way that they radiate in opposite directions, i.e. to the left and to the right of the listener. It turned out that the best results are achieved by a housing with a triangular cross-section (see the drawing), divided by a wall into two parts. This solution can be compared to the radiation of sounds by one source, in principle omnidirectional, but the sounds radiated to the left and right and their reflections differ due to the fact that they correspond to different stereo channels.
DISTORTIONS CAUSED BY ELECTROLYTIC CAPACITORS (2)
When designing electronic circuits, capacitors are considered linear elements. This does not correspond to reality, especially in the case of electrolytic capacitors, which under certain conditions may cause nonlinear distortions. This is the subject of this article.
We know that the capacitance of electrolytic capacitors varies significantly with temperature changes (it decreases rapidly at subzero temperatures) depending on the frequency of the alternating current. The capacity of a good, fully functional and formed electrolytic capacitor changes slightly depending on the value of the DC bias voltage, as shown in the figure.
It follows that in the case of electrolytic aluminum capacitors there is an increase in capacitance with an increase in the polarizing voltage, and in the case of tantalum capacitors - on the contrary, there is a decrease in capacitance.