Stevenson: Liquid cooling is a boon for efficiency | Panda Anku

When planning an RF job, be sure to consider the entire setup

Published: August 30, 2022

A current e-book from Radio World Explored trends in broadcasting and best practices for planning a broadcast purchase. This story is an excerpt.

Don Stevenson is the Chief Engineer for Radio One Dallas/Reach Media.

radio world: If you are considering a purchase or have asked for advice on purchasing a transmitter, what is your overall philosophy or approach?

Don Stevenson: Start your search by looking for equipment manufacturers with a proven track record of reliability. Determine the required power levels for the desired mode of operation. If you design an FM transmitter, do you also do HD? If yes, how will you create the HD? If low-level combining is used, make sure you have enough transmit power to handle it.

Once you’ve narrowed down your choices, consider the efficiency of the transmitter and the overall system. Higher efficiency lowers operating costs, and the operating cost savings should be considered when purchasing the transmitter.

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

RW: What should someone who hasn’t bought a radio station for a while know?

Stevenson: Solid state transmitters are much more efficient than tube transmitters. As more and more of the aging tube transmitters are replaced by solid-state models, tube prices are rising. With tube prices rising, the economic rationale for the decision to go solid state is becoming clearer every day.

Pump stands for the liquid-cooled transmitter.

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

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

RW: What prejudices do many people have about stations that you would like to get rid of?

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

When replacing a transmitter, the operation of the entire transmitter system must also be taken into account. This includes the HVAC system. A liquid-cooled transmitter removes a significant portion of the heat load from the building. This saves less electricity to cool the building and less runtime of the existing systems. This reduces HVAC maintenance expenses and extends the overall life of the systems.

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RW: The concept of efficiency is often debated, but many managers may not fully understand what it means. Why does it matter?

Stevenson: Efficiency is a method that engineers can use to measure operating costs before equipment is purchased. The concept is very important as this is the largest power consumer in the transmitter. Transmitter efficiency is often measured by comparing the electrical power going into the transmitter and the RF power going out of the transmitter. The power lost in the transmitter manifests itself as heat. With an air-cooled transmitter, this hot air is usually vented into the transmitter room or vented outside.

Foreground, valve assembly and piping for the liquid cooling system. Background: HF combiner for the two transmitters.

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

Stevenson: Tube transmitters are becoming more and more expensive to maintain. This is because tube costs are constantly increasing and quality seems less consistent than many years ago.

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

The benefit of using a solid state transmitter is that it uses many amplifiers and power supplies to generate the power. A failure often only leads to reduced performance. A tube transmitter has only one power amplifier and a failure leads to the total failure of the transmitter.

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