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transmission special report


Choice of transmitter cooling technology


The choice between an air cooled and liquid cooled transmitter has a high impact on the total cost of ownership, particularly if only one type of cooling is used throughout the broadcast transmission facility. The energy consumption of a liquid cooling system is a small fraction of the energy consumption of an air cooling system that moves a similar amount of heat from the building. As additional new transmitters are added to a facility with existing air conditioning, there will be little need to add additional air conditioning capacity, but the inefficiency of the existing air conditioning system will still dominate the facility cooling system energy consumption. If a new facility or an existing facility is converted to all liquid cooled transmitters, the amount of air conditioning can be dramatically reduced to remove only the small amount of latent heat from the transmitters and auxiliary equipment racks. Liquid cooled transmitters typically


have twice the power density, per unit volume, of comparable air cooled technology. This is because the volume needed by the open area of the air cooled heat sinks is compressed down to the thickness of the liquid cooled chiller plates. A 2:1 reduction in floor space and vertical height (volume) can significantly reduce the cost of facility space especially in high rise buildings. Figure 3 and Figure 4 show examples of current production liquid cooled UHF power amplifier modules. Figure 5 shows how liquid cooled PA modules are integrated into a complete transmitter system.


Summary


In configuring a transmission system there are a number of critical decisions to be made from the selection of transmission equipment - efficiency and cooling to the cooling technology used in transmitter, which have a large impact on TCO. In addition to the initial hardware cost, broadcasters should consider all acquisition, operating and maintenance costs, all elements in power consumption budget and the necessary building volume and floor space needed to house the transmission equipment. Harris has developed a prototype


www.ibeweb.com l september/october 2012 l ibe l 77


tool to make is easier to analyse and calculate the total cost of ownership for a broadcast transmission facility. This tool brings into focus many of the costs of facility operation that are often ignored when planning a new facility or upgrading an existing facility. When finalised, this tool will help the transmission facility designer make the right design choices to reduce the total cost of ownership.


References


• Freescale Semiconductor White Paper: ‘50 Volt LDMOS - an ideal RF power technology for ISM, broadcast and radar applications’. • Transmitter efficiency: Overview. Retrieved from http:// te.cavellmertz.com/index_js.php. • Total cost of ownership (6 January 2012). In Wikipedia, The Free Encyclopedia. Retrieved from http://en.wikipedia.org/w/index.php title=Total_cost_of_ownership&oldid= 469902093. • McLane, Paul: ‘This calculator is ‘Cool Stuff’ - Radio World, 06.01.2001. www.rwonline.com/article/this- calculator-is-%E2%80%98cool- stuff/23605. • Federal Electronics Challenge - www.federalelectronicschallenge.net/ resources/docs/costofown.pdf. • Total cost of ownership - http://techwise-research.com/types- of-studies/total-cost-of-ownership-tco.


Figure 4: liquid cooled UHF PA module.


Figure 5: liquid cooled UHF


transmitter - front view.


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