Bay-Area Stations Dial Dielectric for Improved DTV Service

Sutro Tower to Support Digital Broadcasts for 11 Stations in San Francisco Bay Area

By Glen Dickson -- Broadcasting & Cable, 12/12/2007 6:48:00 PM

Antenna manufacturer Dielectric was tapped by a consortium of San Francisco stations to build an upgraded digital-antenna system at the Mount Sutro master-tower site that will improve digital-TV reception across the Bay area and potentially help to facilitate DTV reception on mobile devices.

Sutro Tower, the company that manages the communal tower on Mt. Sutro that supports digital broadcasts for 11 Bay-area stations, selected Raymond, Maine-based Dielectric to supply it with new antennas, combiners and transmission lines as part of a three-year, $12 million project that will overhaul the tower’s DTV facilities.

Besides installing new transmission lines and combiners that can support full-power operations for all 11 DTV stations, the project will also mount a new elliptically polarized panel antenna system that can transmit DTV signals with a mix of horizontal and vertical polarization -- sending signals in both the horizontal and vertical planes.

The elliptically polarized antenna, which was just developed by Dielectric, is a key piece of technology, Sutro Tower general manager Gene Zastrow said, and it was picked by Bay-area broadcasters with future mobile DTV services in mind. He added that the DTV signals radiating from the tower will probably be 75% in the horizontal plane and 25% in the vertical plane.

“One of the reasons why we decided to go with the elliptically polarized antenna is that we’re looking forward to portable and mobile receivers,” Zastrow said. “Theoretically, vertical polarization will help reception with those kinds of devices, as those types of single, telescoping antennas tend to be vertical.”

Dielectric, which created Sutro’s existing DTV facilities back in 1998, will first create an auxiliary antenna system for DTV stations, which currently don’t have a backup to the existing four-panel antennas that broadcast DTV. That work, which is already in the planning stages, is scheduled to be completed in the third quarter of 2008.

After analog broadcasts cease Feb. 17, 2009, Dielectric will then start replacing the old batwing-style VHF antennas and slotted UHF antennas currently used for analog broadcasts with the new elliptically polarized panel antenna system -- a process that should be completed by the end of 2009.

Only one San Francisco station, ABC owned-and-operated KGO, will use its existing analog VHF assignment for DTV operations. The analog antennas occupy higher and, thus, better spots on Sutro Tower, and stations would like to move their digital antennas there long-term for optimal high-power DTV operations.

At one point in the next two years, Zastrow said, Sutro Tower will probably simultaneously bear four discreet TV-antenna systems -- the existing primary analog and backup analog antennas and the existing primary DTV and new auxiliary DTV antennas. But things should get less cluttered after the analog units are removed.