Dynamic carrier control (DCC) is a method of reducing power consumption in

radio transmitter In electronics and telecommunications, a radio transmitter or just transmitter (often abbreviated as XMTR or TX in technical documents) is an electronic device which produces radio waves with an antenna with the purpose of signal transmissio ...

s during periods of low audio activity or silence. It is a type of Modulation-Dependent Carrier Level control, or MDCL. All modern high-power (>50 kW)

shortwave Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (app ...

s incorporate DCC of some kind, as well as some

mediumwave Medium wave (MW) is a part of the medium frequency (MF) radio band used mainly for AM broadcasting, AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. Duri ...

(MW) transmitters. DCC causes the

carrier wave In telecommunications, a carrier wave, carrier signal, or just carrier, is a periodic waveform (usually sinusoidal) that conveys information through a process called ''modulation''. One or more of the wave's properties, such as amplitude or freq ...

level to be automatically reduced when the

audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum *Digital audio, representation of sound ...

is very weak or no audio is present. During periods of

silence Silence is the absence of ambient hearing, audible sound, the emission of sounds of such low sound intensity, intensity that they do not draw attention to themselves, or the state of having ceased to produce sounds; this latter sense can be exten ...

(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 electricity.

History

This

amplitude modulation Amplitude modulation (AM) is a signal modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the instantaneous amplitude of the wave is varied in proportion t ...

(and vestigial SSB modulation)

energy-saving Energy conservation is the effort to reduce wasteful energy consumption by using fewer energy services. This can be done by using energy more effectively (using less and better sources of energy for continuous service) or changing one's behavi ...

mode was devised in the late 1930s. The system was originally referred to as the Hapsburg Carrier System. DCC was not implemented in transmitter designs until the 1980s, because of some of the complexities of the control circuit. * DCC's development is linked to

NATO The North Atlantic Treaty Organization (NATO ; , OTAN), also called the North Atlantic Alliance, is an intergovernmental organization, intergovernmental Transnationalism, transnational military alliance of 32 Member states of NATO, member s ...

nations trying to save energy as a result of the ripple effects of

OPEC The Organization of the Petroleum Exporting Countries (OPEC ) is an organization enabling the co-operation of leading oil-producing and oil-dependent countries in order to collectively influence the global oil market and maximize Profit (eco ...

related oil supply

crises A crisis (: crises; : critical) is any event or period that will lead to an unstable and dangerous situation affecting an individual, group, or all of society. Crises are negative changes in the human or environmental affairs, especially when ...

. * DCC is still an option on all shortwave transmitters sold on the

open market The term open market is used generally to refer to an economic situation close to free trade. In a more specific, technical sense, the term refers to interbank trade in securities. In economic theory Economists judge the "openness" of markets a ...

today, since it is almost universally mandated by the purchasers of shortwave transmitters. *

Eastern Europe Eastern Europe is a subregion of the Europe, European continent. As a largely ambiguous term, it has a wide range of geopolitical, geographical, ethnic, cultural and socio-economic connotations. Its eastern boundary is marked by the Ural Mountain ...

manufacturer Manufacturing is the creation or Production (economics), production of goods with the help of equipment, Work (human activity), labor, machines, tools, and chemical or biological processing or formulation. It is the essence of the secondary se ...

s of shortwave transmitters tended not to adopt DCC because

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

in particular had no energy crises, due to its abundant supply of oil.

MDCL methods

There are two types of Modulation-Dependent Carrier Level (MDCL) control methods: DCC, as discussed above, and Amplitude Modulation Companding (AMC), developed by the

BBC The British Broadcasting Corporation (BBC) is a British public service broadcaster headquartered at Broadcasting House in London, England. Originally established in 1922 as the British Broadcasting Company, it evolved into its current sta ...

. The AMC design achieves the opposite effect of the original DCC system: the carrier is at maximum when no audio is present, and is reduced by up to 75% when the audio is loudest. The system uses the carrier to quieten the channel when no audio is present, while still realizing power savings. Both DCC and AMC have been a staple in European MW broadcasting for many years, and now AMC is now being used by stations in North America. Both the above MDCL methods (DDC and AMC) can be used simultaneously if desired. Some stations choose a mixture of DCC and AMC which uses a complex carrier vs. modulation curve, typically running less carrier for modulation in the 25% to 75% range, and with more carrier during peaks and pauses. DCC can work with

frequency modulation Frequency modulation (FM) is a signal modulation technique used in electronic communication, originally for transmitting messages with a radio wave. In frequency modulation a carrier wave is varied in its instantaneous frequency in proporti ...

(FM), but was never adopted for high-power

FM stereo FM broadcasting is a method of radio broadcasting that uses frequency modulation (FM) of the radio broadcast carrier wave. Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to transmit high-fidelity sound ...

transmission.

Advantages and disadvantages of MDCL methods

The main reason for using either MDCL method (or the combination of the two) is to save power and money. Alternatively, for the same total power consumption, the transmission coverage can be somewhat improved. The AMC method has two other advantages. It limits the peak voltages on transmitter and antenna circuits, possibly preventing damaging arcs. Also, if the degree of AMC is properly adjusted, the power drawn from the mains can be kept nearly constant with modulation. This is especially important when operating from a local generator. With conventional DCC the load variations on a generator are made worse. With both methods, the main disadvantage is marginal loss of coverage, comparable to running slightly less power. Also in lower signal strength parts of the coverage area, a station using Dynamic Carrier Control may be more likely to be skipped on digital-tuned radios during seek/scan tuning (if the frequency is passed during carrier reduction), an issue compounded by manual tuning (instead of seek/scan) selection not being easy on some receivers.

Operational use

When running a transmitter with DCC, these settings are recommended (according to whom?) to optimize power savings versus the listener's receiver "signal lock" loss. * DCC (attack, decay) : instantaneous * DCC (carrier power suppression): 3dB (for third- hop targets) * DCC (carrier power suppression): 6dB (for first-hop targets)

Transmitters using DCC

Here is a list of manufacturers that offer DCC in their transmitters: * Ampegon AG (Ex-

Thales Thales of Miletus ( ; ; ) was an Ancient Greek philosophy, Ancient Greek Pre-Socratic philosophy, pre-Socratic Philosophy, philosopher from Miletus in Ionia, Asia Minor. Thales was one of the Seven Sages of Greece, Seven Sages, founding figure ...

) *

Continental Electronics Continental Electronics is an 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 signific ...

Nautel Nautel Ltd. is a Canadian manufacturer of AM and FM radio broadcast transmitters, navigational radio beacons, Differential Global Positioning System (DGPS) transmitters, NOAA Weather Radio, NOAA weather radio transmitters, LF PNT/Loran-C#eLORAN, ...

* RIZ *

Telefunken Telefunken was a German radio and television producer, founded in Berlin in 1903 as a joint venture between Siemens & Halske and the ''AEG (German company), Allgemeine Elektrizitäts-Gesellschaft'' (AEG) ("General electricity company"). Prior to ...

* Transradio ;Analog modes: *A3E AM (incl. DCC) *H3E SSB *R3E SSB According to the

ITU The International Telecommunication Union (ITU)In the other common languages of the ITU: * * is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established ...

Radio Regulations, Geneva 1990, Article 4.

References

{{Reflist Radio technology