In A Repacked World, Size And Power Matter

Many broadcasters assigned new channels as part of the FCC’s TV band repack may need more transmitter power than they think, the RF experts say.

It’s all a matter of physics and physical space on towers.

Stations that move to lower frequencies will need longer antennas and their current towers may not be able to accommodate them. It’s a particular problem for stations that lease antenna space on towers and have to share space with other broadcasters.

“Consider this hypothetical scenario,” says Rich Redmond, chief product officer at GatesAir, one of the major transmitter manufacturers. “You are transmitting on ch. 48 and because of the frequency or wavelength being used, the antenna producing the desired gain may require up to 80 feet on the tower given a certain amount of transmitter power.

“If you move to ch. 24, the wavelength is longer because the frequency is lower. To get the same amount of gain, you may need to have 120 feet of tower space for the antenna, but you only have 80,” he says.

The solution is to transmit at a higher power because there is no overcoming the lack of physical space on the tower for a bigger antenna, unless the station moves to a new structure, he says.

Further complicating things are more stringent structural requirements for TV towers, which mean smaller, lighter antennas will often be required. Again, the solution to achieving the desired signal strength — effective radiated power — and maintaining coverage will be more transmitter punch.

This story originally appeared in TVNewsCheck’s Executive Outlook, a print publication devoted to the future of broadcasting. Subscribe here. Read the other stories in the Winter 2016 issue here.