Dielectric, a manufacturer of broadcast antennas and RF systems for TV and radio, has shipped two stacked antenna arrays to American Tower for repack projects, in the Dallas and Boston broadcast markets. The antennas incorporate Adaptive Polarisation Technology (APT), allowing individual broadcasters to select their own polarisation ratio independent of the other stations operating in the same array. The addition of the vertical component will be beneficial to improving reception for both ATSC 1.0 and future ATSC 3.0 over-the-air broadcasts.
The stacked antenna arrays are anchored by TUM-APT Series UHF panel antennas for American Tower’s master antenna TV station clients, with customised antennas for other TV stations on top of the stack. The Dallas repack project includes a dual-channel, center-fed, elliptically polarised TFU series UHF array for KUVN-DT and KSTR-DT on top, whereas the Boston repack installation adds a circularly polarised TDM series VHF array for WGBY-DT above the TUM-APT.
The stacked arrays offer improved azimuth pattern performance over the more traditional main and sidemount antenna system, which can disrupt the azimuth pattern and cause signal reception issues due to the tower structure. The TUM-APT is designed to incorporate the transmission line for the top mount inside the mast. This line is traditionally outside the mast, causing the azimuth pattern to become distorted.
Dielectric’s flexible TUM-APT panel antenna designs also allowed station engineers to optimise the polarisation ratio post-installation. Changes are made in the combiner room, with no antenna modification required to incorporate a change in the polarisation ratio. As an example, some stations decided to go into the array with horizontal polarisation only based on the current customer base, but want the option to use elliptical or circular or polarisation in the future. That becomes important as the broadcast landscape changes, and viewership with mobile devices increases.
“Most antennas of this nature require that the polarisation ratio is defined and locked in upfront,” said Jay Martin, VP - Sales, Dielectric. “While these arrays are optimised for ATSC 3.0 broadcasting in the future, they will provide increased power density to improve indoor reception for today’s ATSC 1.0 broadcasts.”