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Two-tiered strategy holds RF interference to a minimum in Denver

While RF usage reached unprecedented levels in Denver for the Democratic National Convention in late August, interference issues were held to a minimum by a two-tiered strategy based on frequency coordination prior to the event and enforcement by a team of volunteers during the political spectacle.

The numbers tell the story. In total, 718 frequencies were used or reserved for use during the convention, said Jim Schoedler, POLCOMM 2008 DNC RF coordinator. They broke down as follows:

  • 207 wireless mic frequencies
  • 144 frequencies used for two-way radio, including repeaters
  • 111 frequencies for RF intercom
  • 96 frequencies for IFB for talent
  • 43 microwave channels
  • 117 held in reserve or identified for other purposes

Schoedler, former chairman of SBE Chapter 48 in Denver, has firsthand experience with the RF environment at INVESCO Field acquired by doing frequency coordination for Denver Broncos games. Based on that experience and spectrum usage site surveys at both venues prior to the conventions, Schoedler knew there wouldn’t be much frequency shuffling required as broadcasters moved from the Pepsi Center to INVESCO Field.

“When I compare the two, we found they are not very different. Both facilities act as a shield to a certain amount of RF and are fairly similar,” he said. That knowledge gave Schoedler confidence that a frequency assigned for use at the Pepsi Center should be acceptable for use at INVESCO, he said.

However, there was one notable exception: use of 7GHz COFDM camera transmitters, he said. “There are STL and TSL signals basically shooting over the stadium,” he said. “Testing by Denver stations revealed that the use of the 7GHz channel for COFDM microwave camera transmission from inside the stadium would interfere with the STL and TSL transmissions passing overhead. To resolve the issue, no 7GHz COFDM camera transmission was allowed at INVESCO Field,” he said.

To listen to a Broadcast Engineering podcast interview with Schoedler, click here.

To listen to a Broadcast Engineering podcast interview with Louis Libin, chairman of the Political Conventions Communications Committee, click here.