| Following the loss of the World Trade Center, WABC-TV needed to replace its transmission facilities serving the New York metropolitan area. As part of this plan, the station wanted to ensure that any future catastrophic loss would not leave it without the ability to maintain full-power-service to its viewing public. The station decided to construct two transmission facilities — one at the Empire State Building (ESB) and the other at Four Times Square (4TS). WABC chose The Systems Group to provide the engineering and implementation services for the baseband systems at both facilities. |
Of both sites, the ESB was the preferred location from an RF perspective, but the building facilities were lacking. After much negotiation, engineering, modifications and construction, the ESB was brought up to a level to support many of the major TV broadcasters in the New York market. Even with these modifications, WABC still had issues with redundancy, reserve power and having all of their transmission facilities in one location.
As a result, the station decided to construct a second transmission facility at 4TS. This facility is essentially a duplicate of the ESB facility.
Although the baseband systems for the transmitters were straightforward, much attention was given to the issue of redundancy, especially in light of the difficulties of returning to air after Sept. 11.
The focus was to provide a high order redundancy to ensure that the station would recover from any potential disaster affecting either of the two locations. The design rule dictated that there be duality for all audio and video systems. All air path electronics were required to have dual power supplies. Any processing device had to have relay bypass to eliminate the loss of signal in case of equipment failure.
All NTSC program feeds are delivered to the transmitters from the 66 St. broadcast center as redundant embedded SMPTE 259 signals. All NTSC signals are encoded at the transmitter to maintain excellent signal quality for broadcast. The DTV signal is delivered as a redundant SMPTE 310 signal and distributed to the primary and secondary exciters. A transmitter-studio link provides both sites with quality control, temporary ENG feeds or facilities monitoring via a security camera system.
At the ESB location, only a backup NTSC transmission cluster can run independently of the primary transmission cluster. The primary and backup facilities are interconnected electronically. However, in times of a serious failure of the primary, the backup transmitter has a completely separate control system, transmission feeds, support systems and a generator.
The station selected Harris Recon for its control system for integrated transmitter controls and status monitoring. The challenge in this case was to provide the required control redundancy corresponding to the multi-transmitter plan at ESB. The engineering team devised a complex scheme to interconnect the primary and backup control systems.
This allowed the primary control system to work as a single system for daily operation, with the backup system working independently if required. This included not only the status of critical transmission systems, but also the secondary monitoring of the base building HVAC, fire and the emergency generator.
The ESB location was completed in late 2003, with the 4TS location completed in May 2004.