In two previous articles (starting here), we’ve discussed liquid cooling in transmitters and its applications. The topic becomes even more interesting when we explore the thermodynamics behind the implementation of such systems generally.

While systems for FM transmitters use “anti-freeze” and small pumps, higher-powered systems (think particle accelerators) use deionized clean water, resin bottles, sidestream purification loops and other technology.

While liquid cooling in transmitters may seem complex to a broadcast engineer, it is relatively simple within the wider universe of liquid cooling, where systems for instance serve major military and government applications.

Liquid cooling is found in the studio as well. Microprocessors and graphic chipsets in computers use liquid-cooling technology to pull the heat off and away from the inside of the case.

Liquid cooling has the advantage of allowing larger fans with slower fan speeds to reduce noise, which could be an advantage in rooms where audio is being created.

Gone are the days when liquid-cooling systems meant cobbling together a computer system and doing plumbing in miniature, always concerned that a leak could destroy the computer.

Computer cases are available with liquid-cooling systems for the processor, video card CPUs and other heat-sensitive components.

These “all in one” systems have the same components as other liquid-cooled systems but on a smaller scale. There is a pump, a fluid reservoir/radiator with fans attached, a CPU water block (the liquid cooling equivalent of a heat sink) and cooling tubes. The unit comes pre-filled with coolant.

Applications might be limited to uses like video editing and gaming, but for many users the bright colors and translucent cases used with liquid cooling are an attraction.

Final thoughts

Several final observations about the use of liquid technology in transmitters.

Lower-power transmitters probably do not need liquid cooling. LDMOS devices provide ruggedized compact efficient solutions for amplifier designs. With each new generation of power supplies, efficiency is improved and heat is reduced.

If a low-power transmitter needed liquid cooling it would probably be to compensate for a very compact design. The systems used in desktop computers would provide examples for these applications.

The RF power level at which you might start to consider liquid cooling seems to be around 25 kW. Even at that level, the general case for liquid cooling would be difficult to make without the additional power requirements of digital radio channels.

But readers who have experience with liquid cooling indicate that the benefits and costs we’ve discussed are worth exploring. They remind us that installation should be done with the help of HVAC experienced personnel but they say cost savings can be significant, with few ongoing issues with liquid cooling, which usually can be addressed by staff engineers.

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