Keeping costs low

The main concern about moving to elevated digital sidebands was that utility bills would go through the roof, not just from increased transmitter power requirements but also from new HVAC demands. We evaluated how efficient, or inefficient, our existing closed air conditioning systems would operate in the new setup.

Summer days in Kansas often exceed 100 degrees, topping out near 115. The HPX transmitters, being FM+HD and the highest power units in our systems, also generate the most heat. We opted to step back several decades and build partitions over the HPX transmitters that would create a plenum at the rear, leaving the front side air-conditioned and the back side ventilated with outside air. This ensures that the brains of the transmitter remain cool without requiring an additional 8 to 10 tons of cooling. This design will significantly reduce utility bills.

The KHCC and KHCD HVAC designs are identical. We positioned the backs of these transmitters into spaces resembling oversized closets, with fans hung on outside building walls. The filtered intake fan near the floor runs at about 2,000 CFM, bringing in outside air and pressurizing the space. A 1,500 CFM exhaust fan high on the outside wall and above the drop ceiling sucks hot air from the transmitter exhaust to the outside.

Radio Kansas is currently testing the extended coverage to mobile radios, the increased building penetration for indoor radios and the behavior of portable radios in both mobile and indoor environments. Initial tests appear promising. With the new systems up and running and operating well, our hope is that the tests prove that elevated sideband levels effectively improve our HD Radio coverage and allow us to freely promote HD Radio services to our listeners.

Jung is director of engineering at Radio Kansas, Hutchinson, KS.