The host broadcaster for the event was Danmarks Radio (DR) which relied on Sennheiser's Digital 9000 for the audio transmission of the show. 96 channels of this digital wireless microphone system were deployed for the contest, the VIP area and the press centre which included part of DR's own 24-channel Digital 9000 system. Then added to this were 28 channels of the 2000 Series for the artists' wireless monitoring.
"Join Us" was this year's motto for the Eurovision Song Contest, which was hosted on Refshaleøen island in the B&W Hallerne, a former shipbuilding hall that was specially converted into a show arena for the contest. With the Eurovision Song Contest 2014, Refshaleøen was transformed into "Eurovision Island", and played host to a colourful ensemble of artists and ESC fans. However, for the technicians the situation initially looked a little less colourful. Unfortunately, the shipyard proved to be an incredibly difficult environment for all users of RF wireless, not only for wireless microphones and monitoring systems.
Jonas Naesby, RF specialist with Sennheiser Nordic, was on site for DR to provide assistance to the broadcaster with the microphone and monitoring set-up. "We knew that the available spectrum was very limited as 22 TV channels were already fully occupied. This made frequency planning slightly difficult - especially as wireless mics were not the only devices that needed spectrum," explained Jonas Naesby. "However, the biggest challenge we faced was unquestionably the hall itself."
Both the walls and roof of the huge shipyard are made of metal - as were the stands that were specially erected for the audience of 12,000. The floor is made up of heavily reinforced concrete and this proved to be considerably more critical than that of standard venues. "Never before have I encountered such a huge amount of reflections and if somebody had told me that they knew of an arena that could affect RF transmission this much then I would never have believed it prior to this experience," continued Jonas Naesby.
With a length of approximately 175m and a height of 70m, the metal hall caused reflections that partially ran over 300m and then hit the receiving antennas with a considerable delay as compared to the direct signal. However, the usual amount of damping did not occur: the indirect signals had much higher signal strengths than typically encountered in music venues. This phenomenon was caused by the metal walls and ceiling, which formed corner reflectors and boosted the signal by in-phase additions.
The wireless technology also had to battle with the general frequency situation in Denmark and nearby Sweden: "Unfortunately, having a lot of reflections within the hall does not automatically mean that your hall is entirely shielded against the outside," explained Jonas Naesby. It proved to be quite the opposite as there were enough gaps and also wooden elements to let RF in - with some frequencies more intense than others.
"We had pretty much optimised everything that was there to be optimised: the fine-tuning of the Digital 9000 system, the antenna positions, everything. And of course conditions improved a bit when the audience was in place," continued Naesby. "In addition, we had also adapted the digital signal processing of the system which meant that even signals that arrived at the receiver extremely late and with high signal strengths were correctly combined with the RF signal that had arrived earlier. This meant that the Digital 9000 firmware was able to detect such critical instances and could cope with such extremely rare prob
