Meteor Scatter

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Graphic representation of communication via meteor scatter

Meteorscatter is a method to increase the range of ultra-short waves by means of reflections on the tracks of burning meteoroids in the earth's atmosphere .

Working principle

Ultra-short waves have a quasi-optical propagation. Due to the curvature of the earth, the spread is limited under normal circumstances approximately to the visible horizon. In order to achieve a range that goes well beyond the visible horizon, one can use the meteors that burn up in the earth's atmosphere. The ionization traces of meteoroids that penetrate the earth's atmosphere and burn up are used as reflectors for the radio signals . Objects that enter the earth's atmosphere from space and burn up from an altitude of around 100 km leave an ionization channel on their orbit. This is very short-lived. Radio rays that hit this ionization channel are reflected. The reflection time can be from a few seconds to about two minutes and depends on the frequency. Connections beyond this are very rare. It can be bridged up to 2500 km.

history

The first meteor scatter observations go back to the first half of the 20th century. Hantaro Nagaoka from the Research Institute for Physics and Chemistry in Tokyo first described reflections of radio waves on meteorite tracks in 1929. Meteorscatter was first used in practice from 1955 to 1960 through the JANET project in Canada. Here a distance of around 1000 km was bridged between Toronto and the Canadian province of Saskatchewan using meteor scatter. The carrier frequency used was 90 MHz. With the emerging use of communication satellites towards the end of the 1960s, meteorscatter lost its importance as a transmission method.

commercial use

The commercial use of Meteorscatter is currently not widespread. Basically, however, Meteorscatter is a cost-effective alternative to expensive satellite transmission if only small amounts of data have to be transmitted and a significant delay in transmission can be accepted. There are currently some uses of Meteorscatter. One example of this is the US Department of Agriculture's SNOTEL network . This is a network of weather stations, which are set up in the Rocky Mountains at sometimes remote locations far away from any telecommunications infrastructure. The measured values ​​are transmitted by means of a meteor scatterer.

Use in the amateur radio service

Amateur radio antennas for 144 MHz

The meteor scatter method is currently used intensively by radio amateurs . Radio operation via meteor scatter takes place mainly on 144 MHz ( 2-meter band ), less often on 50 MHz ( 6-meter band ) or 432 MHz ( 70 cm band ). Telegraphy in particular was used at very high speeds until recently. This was initially given with electronic memory keys, later also with PCs. In the past, tapes that were recorded slowly were played at a very high speed for broadcasting. After receiving the pings (less than a second) or bursts (equal to or greater than a second), as the phenomena are called, the fast recordings were allowed to run more slowly and the transmission was deciphered. This was very time-consuming and required a high level of radio discipline on the part of both radio partners, because one had to send several minutes and the other received at the exact time. In the meantime, the digital operating mode WSJT has largely replaced high-speed telegraphy. One of the advantages of WSJT is that radio connections are made possible with very low output powers and also outside of meteor showers .

literature

  • Walter F. Bain: VHF meteor scatter propagation. In: QST, April 1957, pp. 20-24, 140, 142.
  • Walter F. Bain: VHF propagation by meteor-trail ionization. In: QST, May 1974, pp. 41-47, 176.

Web links

Individual evidence

  1. ^ Karl Rothammel : Rothammels Antennenbuch . Newly edited and expanded by Alois Krischke. 12th updated and expanded edition. DARC-Verl., Baunatal 2001, ISBN 3-88692-033-X ( online ).
  2. Hantaro Nagaoka: The Possibility of radio Transmissions Being Disturbed by Meteoric Showers , published in the series Proceedings of the Imperial Academy ; Issue 5, 1929, pp. 233-236
  3. ^ Davis, Gladys, Lang, Luke, Taylor: The Canadian Janet System , Appeared in Proceedings of the Institute of Radio Engineers Volume 45, Issue 12, 1957
  4. Fukuda, Mukumoto, Yoshihiro et al .: Experiments on meteor burst communications in the Antarctic , research report, from page 120, published in the series Advances in polar upper Atmosphere Research at Natl. Inst. Polar Research, Tokyo, 2003
  5. ^ SNOTEL And Snow Survey & Water Supply Forecasting. (PDF; 1.1 MB) (No longer available online.) National Water and Climate Center, March 2009, p. 2 , archived from the original on February 14, 2013 ; Retrieved December 19, 2012 (American English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.wcc.nrcs.usda.gov
  6. Eckart Moltrecht : How does Meteorscatter work? In: German Amateur Radio Club (Ed.): CQ DL . The amateur radio magazine. No.  11-2001 . DARC Verlag GmbH, November 2001, ISSN  0178-269X , ZDB -ID 124446-2 , p. 803 .