In 2004 RTL’s Marnach site installed two new solid state transmitters Telefunken Sendersysteme Berlin S4006, each transmitter is capable of 120 kW DRM or 300 kW AM on 1440 kHz (208 metres). The old 600 kW Telefunken Pantel S1445 transmitters are not DRM capable, although in AM the output of the two new transmitters can be combined with one of the old transmitters (PWM modulator) for a total of 1200 kW AM output power.
Two Telefunken DRM transmitters
Telefunken DRM exciter
During the day both transmitters are used to provide 240 kW DRM feeding the directional antenna beaming 45° towards the Köln/Düsseldorf area. The antenna system consists of 3 guyed phased array, each 1/2 wavelength high (105 metres), with 1 radiator and 2 passive reflectors.
At night time only one transmitter is used feeding 120 kW (DRM) or 300 kW (AM) to the antenna. This antenna consist of a 1/4 wavelength omni-directional radiator with a single passive reflector.
In the old days of Radio Luxembourg it was used mainly for broadcasts to the UK, so the pattern has a slight gain towards the north-west and some attenuation towards Frankfurt/Munich. It also has a higher take-off angle to reduce the fading zone caused by the simultaneous reception of ground wave and sky wave (AM).
QSL card shows the 'night time' antenna used to transmit Radio Luxembourg to the UK.
On the 1st January 2005 RTL and for several days after started broadcasting DRM on 1440 kHz (208 metres) medium wave with ‘RTL Radio - Die besten Hits mit Gefühl’. Mode B was used starting at a bitrate of 18.4 kbps (protection level 1). During the broadcast the protection mode was switched to level 0 (more robust) which improved the reception but reduced the audio quality.
During daytime broadcasts Mode A is preferred but at night the sky wave signal can be received were the channel’s Impulse Response exceeds Mode A’s guard interval (2.6 mSec) so Mode B is used.
With these test transmissions RTL had plans to resume the English service Radio Luxembourg (which had closed end of December 1991) using DRM on 1440 kHz. RTL had hoped that DRM receivers would become available but this did not happened and RTL give up on DRM. This transmitter site is now closed and last of these iconic masts were demolished February 2016.
[thanks to Michel Asorne at BCE for the photos]