A Foundation for the Future

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High beams

A rear view of the support racks for the WINK-FM and WINK-DT transmitters.

The combiner network combines the output of the two 30kW transmitters to produce the 60kW output.

An overhead view of the HTD60 FM transmitter

The multiple changes and modifications to the tower between antennas and transmission line required a significant amount of tower strengthening prior to installation. Tower Innovations engineered the tower strengthening project, which required heavier cross members in certain areas and additional plates on older cross members to support the weight of the new and old antennas and associated transmission line. Tower Innovations provided the cross members and plates, with Dielectric providing the transmission line.

The new portion of the transmission facility spans about two stories from floor to ceiling. This left plenty of space above the transmitters for the line to shoot up and across the ceiling to the exit port, where it continues outside and to the tower bridge. A 6⅛" transmission line was used to handle the 54kW TPO for the WINK-FM transmitter, along with 3⅛" line for DTV transmission. This added quite a bit of weight to the existing 6⅛" analog TV line and 3⅛" FM line for the HT-25 transmitter.

While built as a standalone entity, the new transmission facility, is separated by a double door entry that allows engineers to move between the new and old rooms. With no room to squeeze a new transmitter, the 2009 shut-off date for analog TV means that all main transmission systems will operate out of the new section. To further emphasize the separate entity feel, each side features its own electrical system, cooling system, transformer and generator.

The original part of the transmitter site uses a diesel-powered generator for backup that came in handy for Hurricane Charley. The new side adds a giant UPS for the new WINK-DT and FM transmitters. A second diesel power generator was installed in February 2007; the HT-25 can also be switched on using the older diesel generator if necessary.

This area is cooled through two redundant Liebert ac units that operate on weekly alternating cycles to preserve the life of the units. One unit can handle the heat loads from the DTV and FM transmitters. A large, mounted exhaust fan and two air louvers were incorporated into the building design in the event of total ac failure. The fan automatically starts if the temperature climbs above the set degree, and the louvers automatically open to exhaust heat from the room and keep the transmitters in operating condition. The room normally operates as a closed system.

This additional failsafe cooling procedure was added due to an experience at another transmission facility that had a total ac failure from the Hurricane Charley power outage. The temperature in the transmitter room exceeded 130° on the engineer's arrival, and the transmitters shut down as a result of the heat. Similarly, four by four glass blocks were incorporated into the design. These blocks line the ceiling and walls, and allow engineers to work by sunlight rather than flashlight in the event of power failure.

The electrical system is designed so everything comes into the new side of the building at 480V and is then stepped down to address various electrical requirements. The transmitters run on less but the tower elevator requires the higher voltage. This also provides extra capacity for WINK-FM's future HD Radio transmitter, which will require a separate antenna. Electrical and floor space is also mapped out for a second DTV transmitter when the current Platinum transmitter moves to backup status. These considerations ensure that we'll never run out of electrical capacity or real estate for future transmission and RF systems for antennas.

The facility also is designed to remain clean, as it does not take in any outside air. The closed ac system eliminates bugs and debris. This all adds up to easier transmitter maintenance. The Harris transmitters require limited maintenance; keeping filters clean of dirt and dust, and paying attention to temperature and discoloration in the wiring jackets are the big issues. The HTD-60 allows us to take down one 30kW transmitter, inspect and clean it, and put it back online before repeating the same steps with the second transmitter. This is far easier than the hard switchover of the older transmitters (for which we also run weekly test loads for maintenance purposes).

Transmitter rack equipment is limited mostly to modulation monitoring, with units provided by Inovonics. An ATI distribution amplifier splits the signal to ensure it feeds the HT-25 in the older building. As we prepare for HD Radio, STL upgrades and additional monitoring and processing equipment will certainly be needed. For now, four years of FCC filings, antenna adjustments, tower strengthening and RF design work has paid off nicely. The new DTV transmitter went on the air on May 30, 2006, with the WINK-FM HTD-60 transmitter following on July 17 — with plans in place for future expansion.

Stuhlmann is the director of engineering of Ft. Myers Broadcasting Company and Meridian Broadcasting, Ft. Myers, FL.

Equipment List

  • Amco equipment racks
  • APC Silicon SL320KG UPS
  • ATI distribution amplifiers
  • Belden wiring and cabling
  • Caterpillar 3412
  • Dielectric stacked FM/DTV antenna (TDM-5FM antenna on top/TW-6B9 TV antenna on bottom)
  • Dielectric transmission line
  • ERI Rototiller antenna, tower
  • Harris HTD60 transmitter, Digit CD, switchless combiner
  • Inovonics modulation monitors
  • Liebert ac units
  • Moseley Starlink STL
  • Orban 9300 audio processors
  • Tower Innovations crossbars and plates

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