Dynamic Carrier Control
Encyclopedia
All modern high-power shortwave
radio transmitters incorporate dynamic carrier control (DCC) of some kind. In addition, some mediumwave
transmitters incorporate DCC.
(and vestigial SSB
modulation) energy-saving mode was devised in the late 1930s. DCC was not implemented in transmitter designs until the 1980s, because of some of the complexities of the control circuit.
level to be automatically reduced when the audio
is very weak or no audio is present. During periods of silence
(no audio), the carrier power is reduced by 50%, so the 250 kW transmitter is putting out a carrier of 125 kW during audio pauses. This carrier power reduction saves otherwise wasted electricity.
There is a BBC mode DCC that behaves the exact opposite to the DCC as it is described above. BBC World Service
and relay stations are the only place where transmitter using the BBC-DCC mode. BBC-DCC is said to work better than plain DCC, as it allows the receiver to remain locked to the carrier.
DCC can work with frequency modulation
(FM), but was never adopted for high-power FM stereo transmission.
Occasional misuses of DCC
has made DCC obsolete for digital audio broadcasting via shortwave. The digital DRM signal always has the same power level, thus making DCC moot.
Analog modes:
According to the ITU
Radio Regulations, Geneva 1990, Article 4.
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
radio transmitters incorporate dynamic carrier control (DCC) of some kind. In addition, some mediumwave
Mediumwave
Medium wave is the part of the medium frequency radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz...
transmitters incorporate DCC.
History
This amplitude modulationAmplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
(and vestigial SSB
SSB
- Organizations :* '* Societas Sanctae Birgittae, the Society of Saint Bridget* Society of the Sisters of Bethany, an Anglican religious order* Statistics Norway, , Norwegian government statistics bureau...
modulation) energy-saving mode was devised in the late 1930s. DCC was not implemented in transmitter designs until the 1980s, because of some of the complexities of the control circuit.
- DCC's appearance is linked to NATO nations trying to save energy as a result of the ripple effects of OPECOPECOPEC is an intergovernmental organization of twelve developing countries made up of Algeria, Angola, Ecuador, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, the United Arab Emirates, and Venezuela. OPEC has maintained its headquarters in Vienna since 1965, and hosts regular meetings...
related oil supply crisesCrisesCrises is the eighth record album by Mike Oldfield, released in 1983. Oldfield's well known hit "Moonlight Shadow" appears on the album.- Album analysis :...
. - DCC is still an option on all shortwave transmitters sold on the open marketOpen marketThe term open market is used generally to refer to a situation close to free trade and in a more specific technical sense to interbank trade in securities.-Use of the term in economic theory:...
today, but it is almost universally mandated by those purchasing the shortwave transmitters. - Eastern EuropeEastern EuropeEastern Europe is the eastern part of Europe. The term has widely disparate geopolitical, geographical, cultural and socioeconomic readings, which makes it highly context-dependent and even volatile, and there are "almost as many definitions of Eastern Europe as there are scholars of the region"...
an manufacturers of shortwave transmitters never adopted DCC because RussiaRussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
in particular had no energy crises, due to its abundant supply of oil.
FAQ
DCC causes the carrier waveCarrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...
level to be automatically reduced when the audio
Audio frequency
An audio frequency or audible frequency is characterized as a periodic vibration whose frequency is audible to the average human...
is very weak or no audio is present. During periods of silence
Dead air
Dead air is an unintended interruption in a radio broadcast during which no sound is transmitted.The term is most often used in cases where program material comes to an unexpected halt, either through operator error or for technical reasons, although it is also used in cases where a broadcaster...
(no audio), the carrier power is reduced by 50%, so the 250 kW transmitter is putting out a carrier of 125 kW during audio pauses. This carrier power reduction saves otherwise wasted electricity.
There is a BBC mode DCC that behaves the exact opposite to the DCC as it is described above. BBC World Service
BBC World Service
The BBC World Service is the world's largest international broadcaster, broadcasting in 27 languages to many parts of the world via analogue and digital shortwave, internet streaming and podcasting, satellite, FM and MW relays...
and relay stations are the only place where transmitter using the BBC-DCC mode. BBC-DCC is said to work better than plain DCC, as it allows the receiver to remain locked to the carrier.
DCC can work with frequency modulation
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
(FM), but was never adopted for high-power FM stereo transmission.
Operational usage
When running a transmitter with DCC, these settings are recommended to optimize power savings versus listener's receiver "signal lock" loss.- DCC (attack, decay) : instantaneous
- DCC (carrier power suppression): 3dB (for third-hopSkywaveSkywave is the propagation of electromagnetic waves bent back to the Earth's surface by the ionosphere. As a result of skywave propagation, a broadcast signal from a distant AM broadcasting station at night, or from a shortwave radio station can sometimes be heard as clearly as local...
targets) - DCC (carrier power suppression): 6dB (for first-hop targets)
Occasional misuses of DCC
- Radio New Zealand InternationalRadio New Zealand InternationalRadio New Zealand International , a division of Radio New Zealand, is the official international broadcasting station of New Zealand. It broadcasts a variety of news, current affairs and sports programmes in English and news in seven Pacific languages...
, due to long-term funding problems, has had to resort to using 6db of carrier suppression, making reception in North AmericaNorth AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
difficult. - DCC can make DXingDXingDXing is the hobby of tuning in and identifying distant radio or television signals, or making two way radio contact with distant stations in amateur radio, citizens' band radio or other two way radio communications. Many DXers also attempt to receive written verifications of reception from the...
SW signals more difficult.
Transmitters using DCC
Here is a list of manufacturers that offer DCC in their transmitters- RIZRizRiz may refer to:*Riz, Iran, a city in Bushehr Province, Iran* Riz, alternate name for Zarrin Shahr, a city in Isfahan Province, Iran* Riz, alternate name for Pariz, a city in Kerman Province, Iran* Riz Ahmed , British film actor...
ZagrebZagrebZagreb is the capital and the largest city of the Republic of Croatia. It is in the northwest of the country, along the Sava river, at the southern slopes of the Medvednica mountain. Zagreb lies at an elevation of approximately above sea level. According to the last official census, Zagreb's city... - ThalesThalesThales of Miletus was a pre-Socratic Greek philosopher from Miletus in Asia Minor, and one of the Seven Sages of Greece. Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition...
- NautelNautelNautel Ltd. is a Canadian manufacturer of AM and FM radio broadcast transmitters, navigational radio beacons, Differential Global Positioning System transmitters, medium frequency telegraph and NAVTEX transmitters, and high frequency amplifiers for dielectric heating applications...
(MW only) - TelefunkenTelefunkenTelefunken is a German radio and television apparatus company, founded in Berlin in 1903, as a joint venture of Siemens & Halske and the Allgemeine Elektricitäts-Gesellschaft...
- TransradioTransradioTransradio is a German radio communication systems producer, specialised in research, development and design of AM, VHF/FM and DRM broadcasting systems....
- Continental ElectronicsContinental ElectronicsContinental Electronics is a major American manufacturer of broadcast and military radio transmitters, based in Dallas, Texas. Although Continental today is best known for its FM, shortwave, and military VLF transmitters, Continental is most significant historically for its line of mediumwave ...
Technological obsolescence
Digital Radio MondialeDigital Radio Mondiale
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...
has made DCC obsolete for digital audio broadcasting via shortwave. The digital DRM signal always has the same power level, thus making DCC moot.
Analog modes:
- A3E AM (incl. DCC)
- H3E SSB
- R3E SSB
According to the ITU
Itu
Itu is an old and historic municipality in the state of São Paulo in Brazil. The population in 2009 was 157,384 and the area is 641.68 km². The elevation is 583 m. This place name comes from the Tupi language, meaning big waterfall. Itu is linked with the highway numbered the SP-75 and are flowed...
Radio Regulations, Geneva 1990, Article 4.