In February 2016, RBR+TVBR offered insight and exclusive details on how the upcoming spectrum auction and subsequent television repack can affect FM owners.
With the NAB’s filing of comments on Friday (10/26) slamming the Commission for how it plans to reimburse FM radio stations, we are pleased to revisit this Media Information Bureau column from a senior RF engineer at Dielectric.
As part of RBR+TVBR‘s outreach on how the upcoming spectrum auction and subsequent television repack can affect FM owners, GatesAir Chief Product Officer Rich Redmond has noted how the upcoming television spectrum auction and repack can affect radio’s bottom line. Many TV stations will relocate to a new channel, requiring significant changes to their transmission infrastructures, and that affects the checkbooks of some FMs on shared towers, too.
Dielectric Senior RF Engineer Dan Fallon says FM owners need to be prepared for the power to be reduced or cut entirely at times. While the antenna work is a concern, other RF repack-driven infrastructure changes come into play as well — affecting your bottom line.
Transmission Line and Tower work
The antenna is naturally the most pressing concern for FM broadcasters, but there are several additional factors to consider when it comes to repack-driven, RF infrastructure changes.
When Dielectric proposes a new system, the weight and wind load of both the antenna and its associated transmission line are supplied to the broadcaster and structural engineer. This information will confirm that the additional weight and sail of the overall system is code-compliant with the tower structure.
Since transmission line is often frequency-specific, there are instances where TV transmission line will require replacement. In some situations, the FM broadcaster may be asked to share its existing line with the TV broadcaster, pending additional capacity. This enables the TV broadcaster to feed an auxiliary side-mount antenna while the reinforcement work to accommodate new TV transmission line proceeds.
Assuming the additional line capacity exists, installation crews can add a tower top splitter to feed separate signals to the TV and FM antennas. In the absence of extra capacity in the FM line, the tower crew may run a temporary air cable to feed the auxiliary antenna.
Meanwhile, FM broadcasters should prepare for disruption if tower reinforcement is required to support additional weight from new transmission line. The weight and length of the new transmission line may vary based on the new channel frequency and associated new antenna. That reinforcement work may be substantial enough to include new braces or guy wires, the latter of which would force broadcasters to go dark on that tower for longer periods.
To add another wrinkle, all reinforcement work must comply with Revision G the TIA-222 Standard. Assurance of code compliancy will cross all structural design and fabrication work on the tower beyond antenna modifications, including antenna mounts, structural components, guy assemblies, insulators and foundations. Calculations of antenna and line wind load will also figure in to Revision G compliance.
FM and TV broadcasters can collectively plan for changes — and it necessary, make accommodations to broadcast from alternative sites — with the appropriate planning. In addition to what is outlined above, Dielectric recommends conducting a thorough line sweep in the RF plant. This enables the site engineer to understand if an existing transmission line can be used at a new channel.
Regardless of how your FM operation is impacted by TV channel relocation, Dielectric and other vendors can provide a completely list of tower and installation crews to support changes across every stage of the RF infrastructure. Any broadcaster facing tower work should have several quotes in and begin mapping out a schedule in the coming months.
During the budgeting stage, FM broadcasters should also learn about reimbursement options if affected by construction, based on funds put aside for broadcasters during the wireless spectrum bidding process. Be sure to explore these opportunities as you map your plan. These funds would have to be part of the budget submitted by the TV station whose channel change is causing the impact to the FM station.
This article originally appeared at RBR.com on Feb. 29, 2016
