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Dynamic carrier control

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This is an old revision of this page, as edited by Eyreland (talk | contribs) at 06:20, 20 November 2006 (→History). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

All modern high power (power > 50 kw) shortwave transmitters incorporate Dynamic Carrier Control (DCC) of some kind.

History

This AM modulation energy saving mode was devised in the late 1930s, but not implimented in transmitter designs until the 1970s and 1980s OPEC oil crisies. DCC is still an option on all shortwave transmitters sold on the open market today, but it is almost univerally madated by those purchasing the shortwave tranmitters.

FAQ

Technical notes on DCC

  • DCC causes the carrier level to be automatically reduced when there are lower levels or no audio.
  • 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 saves otherwise wasted empty carrier power.
  • There is a BBC Mode-DCC that behaves the exact opposite to the DCC as it is described above. BBC World Serice and VT Merlin relay stations are the only broadcasters using this DCC mode.
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