Hitachi-Comark Raises RF Questions Ahead of Repack

Hitachi Kokusai Electric Comark LLC has a long standing history in the broadcast TV market. COMARK started more than 45 years ago manufacturing RF components for UHF transmitters and branched out to design and deliver full TV transmission systems. Hitachi-Comark has been involved in many innovations that have revolutionized the market. They are the only transmitter manufacturer to win multiple technical Emmy awards including for the Klystrode tube transmitter and for Digital Modular Adaptive Precorrection (DAP).

Over the last 24 months Hitachi-Comark has been preparing for the FCC repack with a full portfolio of equipment and services. For DTV transmitters, Hitachi-Comark and its sister organization Hitachi Kokusai Linear have introduced two highly efficient Doherty solid state transmitter designs: Parallax liquid cooled and E-Compact air cooled. Both products utilize “repack optimized” broadband Doherty RF amplifier designs.

Beyond amplifier technology, what else should broadcasters look for when evaluating their repack DTV transmitter needs? The FCC has indicated that they will replace “like-for-like” in terms of equipment. Below is a quick list of questions that all broadcasters should be asking before purchasing their DTV transmitters.

Does your current or future repack transmitter provide the ability to upgrade/increase the RF output power easily and cost effectively? It should if you are migrating from a horizontal polarized antenna to a newer model with elliptical polarization (adding a vertically polarized component). E-Pol provides added benefit of improved indoor and mobile coverage through its higher power density. Systems like the Parallax utilize a modular design to accommodate customer requirements to increase their power by providing upgradability in terms of adding additional amplifiers or cabinets. Flexibility in design is critical, be sure that your new transmitter is easily upgradeable and expandable and cost effective.

The ATSC has done a tremendous job of bringing ATSC 3.0 from concept to standard in record time. Repack does not mean that stations will start off immediately broadcasting ATSC 3.0; there will be a transition from ATSC 1.0 to 3.0 in the future. The Hitachi-Comark Exact-V2 exciter platform is IP Optimized that features seven Gigabit Ethernet ports. The exciter is compatible with the STL interface (A/324) plus it offers (optional) built-in ALP encapsulation. It features “DualCast” technology, which is easily upgraded from ATSC 1.0 to 3.0 protecting investment today for use tomorrow by a simple software upgrade, no hardware required. Be sure you understand the impacts of upgrading to ATSC 3.0 but also the cost implications (hardware, software, or both). 

There are practical limits to air cooled transmitters due to size and waste heat load. However, if your TPO is between 5 and 10kW, either an air or liquid solution can be utilized. Generally, an air cooled transmitter will be quicker to install but they use the room’s air conditioning (and associated HVAC capacity) to keep the transmitter cooled. Beyond 10kW, liquid cooled DTV transmitters are more practical since the waste heat is moved outside of the transmitter building with an external liquid to air heat exchanger. Consider possible implications that liquid cooling brings to installation and site work including cooling system component location (indoor and outdoor), interconnect plumbing routing and building penetrations.

Moving from your current RF channel to a new one is cumbersome enough. However, have you considered what RF channels your in-market neighbors will be using? And are these channels adjacent to your new channel? If so, then you should be working with your transmitter supplier to be sure that the proper filter is used and rated for both adjacent channel operation (typically 8-pole filter) but also for future ATSC 3.0 operation. Also, if you have been allocated channel 14, there will likely be additional RF mask filtering requirements to protect adjacent wireless services.

No one knows your transmitter site like you do. However, it’s a good idea to have a third party complete a site survey and prepare a system design review. This service is designed to evaluate the current transmitter facility in terms of space, electrical capacity, delivery access, HVAC capacity, transmitter sub-system locations (indoor and outdoor) as well as equipment de-commissioning and removal. Having a vendor such as Hitachi-Comark prepare the System Design Review ensures that lines of demarcation are known and eliminates surprises. Best of all, this service is an expense that can be reimbursed through the FCC 399 budget submittal.

While this is not an exhaustive list, it does cover the major points that all broadcasters should be considering as we enter this very busy time. Hitachi-Comark offers broadcasters more options, more solutions and more services to help broadcasters through the upcoming FCC repack. Visit to learn more about Hitachi-Comark and its RF technologies and associated products.

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