Dielectric, the 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 Polarization Technology (APT), allowing individual broadcasters to select their own polarization 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 customized antennas for other TV stations on top of the stack. The Dallas repack project includes a dual-channel, center-fed, elliptically polarized TFU Series UHF array for KUVN-DT and KSTR-DT on top, whereas the Boston repack installation adds a circularly polarized TDM Series VHF array for WGBY-DT above the TUM-APT.
Dielectric’s antenna system design delivers two substantial benefits in both cases. 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. By stacking the antennas, both systems transmit into free space as true top-mounted arrays, allowing for a stronger, interference-free pattern with no tower scattering effects. 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 optimize the polarization ratio post-installation. Changes are made in the combiner room, with no antenna modification required to incorporate a change in the polarization ratio. As an example, some stations decided to go into the array with horizontal polarization only based on the current customer base, but want the option to use elliptical or circular or polarization in the future. That becomes important as the broadcast landscape changes, and viewership with mobile devices increases.
Both American Tower master antennas have bandwidth and extremely high power handling capacity to accommodate additional stations and their unique polarization needs in the future.
“Most antennas of this nature require that the polarization ratio is defined and locked in upfront,” said Jay Martin, Dielectric’s Vice President of Sales. “The TUM-APT panel antenna offers our customers an enormous advantage by allowing for polarization ratio changes inside the transmitter room. And while these arrays are optimized 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.”
Dielectric’s engineering expertise also ensured that the TUM-APT structure can support the heavier weights of stacking an additional array on top, thanks to specially designed splines that can support both arrays from a single installation point. Martin adds that both antenna systems were designed for helicopter lifts to expedite the installation process.
The antennas are scheduled to go on the air this summer following the installation of transmission line and RF systems.