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{{Short description|Type of spark gap modulation}}
A '''damped wave''' is an [[Electromagnetic radiation|electromagnetic wave]] whose [[amplitude]] of [[oscillation]] decreases with time, eventually going to zero. This term also refers to an early method of [[radio transmission]] from [[spark gap transmitter]]s, or other types of transmitters having characteristic decrement similar to spark transmitters, in which a [[carrier wave]] is switched on and off. This is generally referred to as "Class B" emission. Information is carried in the rhythm and spacing with which the signal is sent. Damped waves were used for a form of [[on-off keying]] (OOK). However, such transmitters were noisy and generated a wide emission [[Bandwidth (signal processing)|bandwidth]].
[[File:Damped Waves.svg|thumb|right|250px|A series of damped waves, such as would be radiated by a [[spark-gap transmitter]]. In this graph, the vertical axis is the amplitude of the wave, in units such as voltage or electric field strength; the horizontal axis is time.]]

A [[Damping#Damped sine wave|damped wave]] was an early method of [[radio transmission]] produced by the first [[radio transmitter]]s ([[spark gap transmitter]]s) which consisted of a series of damped [[radio wave]]s. Information was carried on this signal by [[telegraphy]], turning the transmitter on and off ([[on-off keying]]) to send messages in [[Morse code]]. Damped waves were the first practical means of radio communication, used during the [[wireless telegraphy]] era which ended around 1920. In [[radio engineering]] it is now generally referred to as "Class B" emission.

Such transmissions have a wide [[Bandwidth (signal processing)|bandwidth]] and generate electrical "noise" ([[electromagnetic interference]]) which interferes with other radio transmissions. Because of their potential to cause interference and their resulting wasteful use of [[radio spectrum]] resources, there is an international prohibition against the use of class B damped wave radio emissions (except in the USA under Part 15: "§15.521 Technical requirements applicable to all UWB devices. (i) The prohibition in §2.201(f) and 15.5(d) of this chapter against Class B (damped wave) emissions does not apply to UWB devices operating under this subpart."), established by the [[International Telecommunication Union]] in 1938.<ref>
{{cite book
| last1 = Siwiak
| first1 = Kazimierz
| last2 = McKeown
| first2 = Debra
| title = Ultra-wideband radio technology
| publisher = John Wiley and Sons
| date = 2004
| location = USA
| pages = 15
| url = https://books.google.com/books?id=SW1hJpjZbDwC&pg=PA15
| isbn = 0-470-85931-8
}}
</ref><ref name=Title47>individual nations enforce this prohibition in their communication laws. In the United States this is implemented in regulations of the Federal Communications Commission: {{cite web
| title = Title 47, Chapter 1, Subchapter A, Part 2, Subpart C - Emissions, footnote f
| work = Code of Federal Regulations
| publisher = United States printing office website
| date = December 14, 1984
| url = https://www.gpo.gov/fdsys/pkg/CFR-2007-title47-vol1/xml/CFR-2007-title47-vol1-sec2-201.xml
| accessdate = February 14, 2018
}}
</ref>
However the definition of "damped waves" in these regulations is unclear when applied to modern technology, and recently there have been moves to amend this prohibition to exempt emerging radio technologies such as [[Ultra-wideband|ultra-wideband transmission systems]].<ref name=FCC>
{{cite web
| title = Notice of Inquiry: Revision of Part 15 of the Commission's Rules Regarding Ultra-Wideband Transmission Systems
| work = ET Docket No. 98-153
| publisher = US Federal Communications Commission
| date = August 20, 1998
| url = http://sss-mag.com/pdf/UWBRULES.pdf
| accessdate = 2010-03-04
}}
</ref>


There is a currently an international prohibition against the use of Class B, damped wave emission. This prohibition forms part of the [[International Telecommunication Union]] regulations and is a throwback to the days when spark gap transmitters were employed. The prohibition against Class B emissions was intended to prevent the generation of wasteful radio frequency energy and the use of inefficient transmission techniques. However, ironically there is no longer a clear definition of a Class B, damped wave emission{{Fact|date=February 2007}}.
== See also ==
== See also ==
* [[Continuous wave]]
* [[Continuous wave]]
* [[Damping ratio]]
* [[On-off keying]]
* [[On-off keying]]
* [[Amplitude modulation]]
* [[Amplitude modulation]]
* [[Types of radio emissions]]
* [[Types of radio emissions]]

== References ==
<references />

== External links ==
* [http://www.zianet.com/sparks/sparkmakers2.html Sparks Telegraph Key Review] A complete listing with photos of damped wave telegraph keys (spark keys) by manufacturer.
* [http://www.zianet.com/sparks/sparkmakers2.html Sparks Telegraph Key Review] A complete listing with photos of damped wave telegraph keys (spark keys) by manufacturer.
* [http://edocket.access.gpo.gov/cfr_2007/octqtr/47cfr2.201.htm 47cfr2.201] FCC rules where "Type B damped wave emissions" are forbidden.
* [http://edocket.access.gpo.gov/cfr_2007/octqtr/47cfr2.201.htm 47cfr2.201] FCC rules where "Type B damped wave emissions" are forbidden.


[[Category:Radio modulation modes]]
[[Category:Radio modulation modes]]
[[it:Onda smorzata]]

Latest revision as of 03:07, 31 January 2024

A series of damped waves, such as would be radiated by a spark-gap transmitter. In this graph, the vertical axis is the amplitude of the wave, in units such as voltage or electric field strength; the horizontal axis is time.

A damped wave was an early method of radio transmission produced by the first radio transmitters (spark gap transmitters) which consisted of a series of damped radio waves. Information was carried on this signal by telegraphy, turning the transmitter on and off (on-off keying) to send messages in Morse code. Damped waves were the first practical means of radio communication, used during the wireless telegraphy era which ended around 1920. In radio engineering it is now generally referred to as "Class B" emission.

Such transmissions have a wide bandwidth and generate electrical "noise" (electromagnetic interference) which interferes with other radio transmissions. Because of their potential to cause interference and their resulting wasteful use of radio spectrum resources, there is an international prohibition against the use of class B damped wave radio emissions (except in the USA under Part 15: "§15.521 Technical requirements applicable to all UWB devices. (i) The prohibition in §2.201(f) and 15.5(d) of this chapter against Class B (damped wave) emissions does not apply to UWB devices operating under this subpart."), established by the International Telecommunication Union in 1938.[1][2] However the definition of "damped waves" in these regulations is unclear when applied to modern technology, and recently there have been moves to amend this prohibition to exempt emerging radio technologies such as ultra-wideband transmission systems.[3]

See also

[edit]

References

[edit]
  1. ^ Siwiak, Kazimierz; McKeown, Debra (2004). Ultra-wideband radio technology. USA: John Wiley and Sons. p. 15. ISBN 0-470-85931-8.
  2. ^ individual nations enforce this prohibition in their communication laws. In the United States this is implemented in regulations of the Federal Communications Commission: "Title 47, Chapter 1, Subchapter A, Part 2, Subpart C - Emissions, footnote f". Code of Federal Regulations. United States printing office website. December 14, 1984. Retrieved February 14, 2018.
  3. ^ "Notice of Inquiry: Revision of Part 15 of the Commission's Rules Regarding Ultra-Wideband Transmission Systems" (PDF). ET Docket No. 98-153. US Federal Communications Commission. August 20, 1998. Retrieved 2010-03-04.
[edit]
  • Sparks Telegraph Key Review A complete listing with photos of damped wave telegraph keys (spark keys) by manufacturer.
  • 47cfr2.201 FCC rules where "Type B damped wave emissions" are forbidden.
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