Radio Communication, Meteor-Burst
Radio Communication, Meteor-Burst
a type of radio communication in which the reflection of radio waves from the ionized trails of small meteors is used. Meteor-burst radio communication is used comparatively rarely—and then mostly to transmit information such as telegraph messages in binary code and to align time in installations that are far apart, by a reciprocal exchange of check signals.
When small meteors pass through the atmosphere, they leave trails of ionized gas, some of which have an electron concentration that is sufficient to reflect radio waves efficiently in the meter wavelength range.
This phenomenon allows radio communication by means of reflections from the meteor trails with the use of relatively low-power transmitters (of the order of 1 kilowatt) and simple antennas having gains of 6 to 18 decibels over distances of up to 1,700 or 1,800 km without relaying. To do this, the transmitters of both correspondents irradiate a certain region at a height of about 100 km above the earth’s surface. When a trail is appropriately oriented, a two-way communication channel is created (Figure 1). This channel has a frequency bandwidth of several tens or hundreds of kilohertz, depending on the power of the transmitters, the sensitivity of the receivers, and an acceptable level of effects from multiple-beam propagation of the radio waves. When the power level for such a channel is high enough, efficient reflections are observed regularly—usually several times a minute with an average duration of several tenths of a second. By using a transmission rate of 5,000 to 10,000 bits per second, it is possible to transmit a relatively large volume of information during these short time intervals, which add up to several percent of the total communication time. Thus, a meteor-burst radio communication channel operating at a frequency of about 40 megahertz can have sufficient capacity for the continuous, stable operation of one or several teletypewriters.
Because of the low absorption of meter waves in the ionosphere and the characteristics of the wave-propagation mechanism, meteor-burst radio communication is much less subject to the effect of ionospheric disturbances than radio communication at decameter wavelengths and has a relatively high directivity (even with weakly directional antennas); thus it is less subject to the interference produced by distant radio apparatus.
The intermittent nature of the formation of the communication channel necessitates the use of special methods for the transmission and reception of messages. Incoming messages are stored and then transmitted in batches at a high rate during the short time intervals when a two-way communication channel exists. The batches of messages are also stored as they are received and then fed into recording apparatus at the usual rate. In addition to storage units there are special units that analyze the signals received in order to determine whether they are suitable for communication and systems that combine the batches of messages received to eliminate losses or duplicated reception of messages at the breaks between batches. To ensure reliable trans-mission, methods of automatic error detection and error correction are used.
REFERENCESMeteornaia radiosviaz’ na ul’trakorotkikh volnakh. Collection of articles edited by A. N. Kazantsev. Moscow, 1961.
Bondar’, B. G., and B. L. Kashcheev. Meteornaia sviaz’ [Kiev, 1968.]
A. A. MAGAZANIK