Radioelektronik

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..

ANNOUNCEMENTS (1)

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.

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Radioelektronik (Radioelectronics) 1989/05

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Radioelektronics, may 1989, volume XL (120), 5'89
Cover: Even when designing shoes, a computer is used (Foto Siemens)

FROM THE COUNTRY AND FROM THE WORLD (cover page 2)

  • Designing footwear using a computer
    "SchuCAM" is the name of a computer program developed by Siemens for the footwear industry. Used by the largest European manufacturer of women's footwear - the Gabor company in Germany - it enables quick reaction to changes in fashion, reducing costs and shortening the development time. Difference to a conventional system? 40 years ago, the company released four new models per season, now - 250 to 350 new models in six months.
  • The new ITT-NOKIA compact disc player
    The DP 7980 player is particularly distinguished by the container for 6 compact discs (CD), which allows you to play music for about 6 hours without interruption. It is possible to program 32 tracks in advance, repeat selected tracks, quickly search for the desired track.
  • Light signal splitters
    Siemens informs that it has developed a technology for the production of glass plates in which fiber optic tracks with branched configuration are formed. The tile is 30 x 5 x 5 mm. The signal attenuation is approx. 0.3 dB / cm and additionally 0.3 dB at the branch.
  • Computer system as a translator
    Experts from the West German concern Siemens have developed a computer system called METAL (Machine Evaluation and Translation of Natural Language) for "intelligent" translation of multilingual texts. Currently, the translation from German to English is ready, and the "reverse" version is in preparation - from English to German, as well as versions covering other languages: French, Spanish and Dutch.

ANNOUNCEMENTS (1)

ELEKTROACOUSTICS - MICROPHONES (3) (2)

  • Special microphones
    Of the many microphones with special features, we will only name a few.
    Wireless microphones: The microphone cable connecting the microphone to the amplifier is especially inconvenient during performances of artists moving on the stage, passing from place to place, etc. Long time ago the idea arose to place a battery-powered radio transmitter in the microphone or close to it, and outside the stage or stage - setting the appropriate receiver, the output of which is normally connected to the mixer and amplifiers.
    Limiting plane microphones: The limiting plane (acoustically) is e.g. the wall or floor of a studio or concert hall. Acoustic waves reflect off such a plane. If a microphone with a very small diaphragm diameter is placed in such a plane, it will exhibit special properties, mainly due to the fact that it does not interfere with the acoustic field in any way. Waves of different lengths come in from different directions, bounce, and travel on. Of course, the directivity characteristic of such a microphone is in the shape of a hemisphere. The figure shows this type of microphone. These microphones are generally designed as condenser microphones. They are distinguished by a very natural sound perception and a good reproduction of the acoustic atmosphere. They are used in studios to pick up a solo instrument (e.g. piano) or small orchestral ensembles.


Studio condenser microphone "limiting plane microphone" - AKG type C562BL

  • Selected recommendations for the use of microphones
    The microphone perceives changes in sound pressure that cause the diaphragm to vibrate. A human being hears with two ears and immediately subjected the received waveforms to extremely complex processing in the brain. It can be said that the microphone "hears" objectively and the human hears subjectively, and these are completely different ways of hearing. You have to remember about this when using microphones.
    In the phonographic and radio studio, an acoustician has a lot of resources at his disposal, enough time for rehearsals and the possibility of using the multitrack recording technique, i.e. preparing the sound material from which the final musical product is made. An extensive knowledge of microphone studio technique has arisen, which is constantly enriched as experience accumulates and new technical means are introduced. This activity is the domain of a fairly small group of specialists.
  • Power
    Condenser microphones require an electrical source. Several solutions are used.
    Condenser studio microphones are supplied in a standardized manner by a derivative (phantom) wire made of the two "signal" wires and a shield connected to the ground of the microphone.


Diagrams of powering condenser microphones through a derivative wire path.

  • Cables as well as plugs and connection sockets
    The microphone cable contains two insulated multi-core conductors (0.2 to 0.6mm2, depending on the type of cable), a shielding braid (often double) and an outer protective layer. The microphone cables are made in such a way that they do not become entangled or looped. The outer diameter of the cable is 4 ÷ 7 mm.


Diagrams of connecting microphones to different plugs

  • a - DIN microphone plug (WM-345) symmetrical connection
  • b - DIN microphone plug (WM-345) asymmetrical connection
  • c - 6.3 mm "finger" plug, asymmetrical connection
  • d - special plug (DIN 41624), symmetrical connection
  • e - Cannon XLR plug, symmetrical connection

UNUSUAL ILLUMINOPHONIC DEVICE (5)

The characteristic features of the illuminophony device described in the article are: the use of Siemens UAA180 integrated circuits (national equivalent of UL1980N) in the device,

Read more: Radioelektronik (Radioelectronics) 1989/05