Transmitters
A number of transmitters were installed on the site over the years, the most powerful being an AEG-Telefunken S4006 which had a maximum output of 600 kW. However, registration listings for both 648 and 1296 kHz always gave 500 kW as the maximum power used on both frequencies.
Transmissions on 648 kHz from the AEG-Telefunken S4006 used dynamic carrier control, an energy-saving technique in which the power of the transmitter's carrier signal is reduced when the audio level is low.
Other transmitters included two Doherty 250 kW units, designated ORF 2A and 2B (both originally at Crowborough), whose outputs could be combined to give 500 kW on a single frequency.
A DRM-capable Nautel NA200 transmitter was commissioned in 2003 and radiated digital signals on 1296 kHz. It was designated ORF 4. Although rated at 200 kW, when operating in DRM mode it generally ran with an output power of 35 kW.
Read more about this topic: Orfordness Transmitting Station