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Stevenson: Liquid Cooling Is a Boon to Efficiency

Be sure to consider the entire facility when planning an RF job

A recent Radio World ebook explored trends in transmission and best practices for planning a transmitter purchase. This story is excerpted. 

Don Stevenson is the chief engineer for Radio One Dallas / Reach Media.

Radio World: When you’re considering a purchase or asked for advice about buying a transmitter, what is your overall philosophy or approach?

Don Stevenson: Start your search by looking for equipment manufacturers with a proven track record for reliability. Determine the required power levels for the type of operation desired. If you are designing an FM transmitter plant, will you also be doing HD? If so, how will you be creating the HD? If low-level combining is used, make sure you have enough transmitter power to handle it. 

Once you have narrowed your selection down, consider the efficiency of the transmitter and the entire facility. A higher efficiency will reduce operating costs, and the savings in cost of operation should to be considered in the transmitter purchase.

Don Stevenson with KZMJ’s 60 kW transmitter, a GatesAir Flexiva model.

RW: For someone who hasn’t purchased a broadcast transmitter in awhile, what should they know? 

Stevenson: Solid-state transmitters are much more efficient than tube-type transmitters. As more of the aging tube-type transmitters are replaced with solid-state models, the tube prices are going up. As the tube prices go up, the economics for the decision to go solid-state become clearer every day.

Pump stands for the liquid-cooled transmitter.

RW: Can you name a feature that you wish transmitter manufacturers would add or make more widely available?

Stevenson: Liquid cooling is very helpful with increasing the efficiency of the transmitter facility. This technology is relatively new to radio, but TV has been doing it for decades. Removing the heat from the building helps in reducing the HVAC load and therefore reduces the overall cost of maintenance of the building HVAC system. 

RW: What misconceptions do many people have about transmitters that you’d like to dispel?

Stevenson: “Liquid cooling is too expensive.” While the cost of a liquid-cooled transmitter is more expensive than an air-cooled transmitter, it will save you money in the long run. 

When replacing a transmitter you must also consider the operation of the entire transmitter facility. This includes the HVAC system. A liquid-cooled transmitter will remove a significant amount of the heat load from the building. This will save in less electricity to cool the building and less run time on the systems in place. This will reduce the amount of money spent on HVAC maintenance and increase the overall life of the systems. 

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RW: The concept of efficiency is often discussed, but many managers may not understand exactly what it represents. Why does it matter?

Stevenson: Efficiency is a way engineers can measure the cost of operation before equipment is purchased. The concept is very important, as this is the greatest consumer of electrical power in the transmitter facility. Transmitter efficiency is often measured by comparing the electrical power going into the transmitter and how much RF power is coming out of the transmitter. The power that was lost in the transmitter is manifest as heat. In an air-cooled transmitter, that hot air is normally exhausted into the transmitter room or vented outdoors.

Foreground, valve assembly and lines for the liquid-cooling system. Background: RF combiner for the two transmitters.

RW: Is availability of parts for legacy transmitters that are still in service a serious problem in our industry? What could be done about it?

Stevenson: Tube-type transmitters are becoming more expensive to maintain. This is due to tube cost constantly rising and the quality seems to be less consistent than many years ago. 

Manufacturers try to support these transmitters as best they can, but the parts are becoming more and more difficult to find for some of the older transmitters. This can result in significant delays in repairing a transmitter. 

The benefit to using a solid-state transmitter is it uses many amplifiers and power supplies to create the power. A failure often times will only result in reduced power. A tube transmitter only has one final amplifier, and a failure will result in a complete failure of the transmitter.

[Check Out More of Radio World’s Ebooks Here]