A trend of today's radio electronics

The reduction of radio instruments to miniature propositions is a major trend in modern radio electronics. The significance of this research has grown especially in connection with space communications. It is impossible to create a spaceship for lights over a long distance or to meet constantly increasing demand for satellites, to provide proper operation of portable computers and mobile phones without light, small and economical devices and apparatuses.

Almost any airplane carries nowadays a large amount of useful equipment for safety flight and its pilots use the great number of devices and sensors controlling different things. The reusable spaceship also carries a lot of equipment: a system for communication with the Earth, radars, life-supporting and experiments conducting systems, etc. And the further development in the field of airplane and spaceships design and construction will not leave much room for bulky equipment in the future.

Semiconductors and integrated circuits have helped to reduce the equipment size considerably. Having replaced the electronic valves semiconducting tools provide less size, weight and more reliability. They consume less power and are more durable. But it does not mean that radio valves were useless invention and they can no longer be developed. Taking into account hearing aids and pocket receivers we can be sure their development was impossible with the use of radio valves.

The emergence of new synthetic materials led to the size reduction of other parts of electronic instruments - resistors, condensers and transformers. For example, there is a wire with a cross section of just a few microns - 1/20 the thickness of a human hair. It can be used in miniature transformers and other elements of radio circuits. The development of micromodules - tiny ceramic plates with a metallized coating - has opened great possibilities for making miniature electronic instruments.

Semiconductors compressed into this plate are hundreds of times smaller than electronic valve. The component density of micromodules is very high and there are radio units with up to 70 parts within a cubic centimeter. A radio receiver assembled of micromodules does not weigh more than 60 grams.

Molecular electronics also opens new possibilities for the further radio electronics development. A crystalline lattice can be changed by proper substance added to semiconductors to obtain crystals with the required electrical properties. Germanium or silicon plates produced by the previously mentioned method will not operate as separate resistors or condensers, but as complete circuits - as generators or amplifiers. In these systems the assembly density will be higher as several thousand parts per a cubic centimeter.

It can be noted that in the nearest future superminiature elements will be developed like models of nerve cells of living organisms - neurons.

The radio system

Radiation through space is the basis of all radio communication, but means must be provided for generating the signal and receiving it at the receiving end. The transmitting station requires a means for generating the radio-frequency energy and this is done by converting direct current or low-frequency alternating current power into radio frequency by means of vacuum tubes and their associated circuits. The radio-frequency energy is fed into a radiating system, or antenna.

To transmit any message the information should be imposed upon the radio-frequency energy. In the case of radiotelephone operations it is done by varying the amplitude of the output in accordance with the voice frequencies of the operator picked up by microphone and amplified. Either by turning the output on and off to form the dots and dashes of the radio code that correspond to the letters of the words that the operator wishes to transmit. Thus the energy radiated from antenna serves as a carrier for the information.

At the receiving station transmitted energy (currents) is introduced into selective circuits which make it possible to select the desired signal out of all that exist in space. These currents are amplified by passing them through the suitable vacuum tube amplifiers that build up the energy level. But to make the signal audible it should be detected with the help of various radio devices.

The audio signal may be amplified after detection and made audible by feeding it into headphones or a loudspeaker.

RADIO

Radio is a system of communication employing electromagnetic waves propagated through space. Because of their varying characteristics, radio waves of different lengths are employed for different purposes and are usually identified by their frequency. The shortest waves have the highest frequency, or number of cycles per second; the longest waves have the lowest frequency, or fewest cycles per second. In honor of the German radio pioneer Heinrich Hertz, his name has been given to the cycle per second (hertz, Hz); 1 kilohertz (kHz) is 1000 cycles per sec, 1 megahertz (MHz) is 1 million cycles per sec, and 1 gigahertz (GHz) is 1 billion cycles per sec. Radio waves range from a few kilohertz to several gigahertz. Waves of visible light are much shorter. In a vacuum, all electromagnetic waves travel at a uniform speed of about 300,000 km (about 186,000 mi) per second.

Radio waves are used not only in radiobroadcasting but in wireless telegraphy, telephone transmission, television, radar, navigational systems, and space communication. In the atmosphere, the physical characteristics of the air cause slight variations in velocity, which are sources of error in such radio-communications systems as radar. Also, storms or electrical disturbances produce anomalous phenomena in the propagation of radio waves.