INTERNATIONAL EDITION Saving Money in High-Power Medium-Wave Operations December 2018 Sponsored by From the Publishers of Radio World International Because Worry-Free Radio Transmission Matters Nautel is a leader in radio broadcasting with robust, easy-to-deploy, digital-capable transmitters. Built-in award-winning control saves you time, trips and money. “The NX Series is field proven with over 26 Megawatts of 90% AM power on-air.” EFFICIENCY Mike Woods Nautel Head of Engineering World’s largest radio deployments rely on Nautel. Learn more at nautel.com INTERNATIONAL EDITION Saving Money in High-Power Saving Money in Medium-Wave Operations High-Power Medium- Wave Operations December 2018 Sponsored by From the Publishers of Radio World International High-power transmission plants for medium-wave broadcasters are specialized technical environments 4 that can be costly and complicated to run. Radio World’s A Chat With Ben Dawson December eBook explores how such operators can save money in managing their facilities. How are worldwide electricity costs changing? What 6 impact is this having on operators of high-power (100 kW+) facilities? How efficient are AM/MW transmit- Kelly: Modern Designs Paul McLane ters that are being used in various high-power installa- Editor in Chief Make a Huge Difference tions? What role do Modulation Dependent Carrier Level algorithms play in high-power MW facilities and what changes might be coming in MDCL? 8 We explored these questions in the stories that follow. Saving Money in High-Power Veteran engineer and consultant Ben Dawson provides general context, Medium-Wave Operations as does Chuck Kelly of Nautel. Robert Webber of BBC World Service shares an overview on present and future AM broadcasting technologies. Davide Moro summarizes the conclusions of a BBC white paper on AM compan- 12 ding. Marco Auriti shares his experiences at Touch Canada Broadcasting The BBC Pushes MDCL Algorithm LP, while Gerhard Straub of the U.S. Agency for Global Media reminds us of Beyond Its Limit the importance of the antenna system. And we conclude with a technical discussion from NAB Radio Engineering Achievement Award recipient Tom King with tips on designing a cost-effective high-power antenna system. 14 My thanks to Davide Moro for his help in creating this eBook. How may our eBooks serve you better? Email me at [email protected]. Touch Canada Experiences Energy Savings With MDCL 16 Don’t Overlook the Antenna System 17 Design a Cost-Effective High-Power Antenna System SAVING MONEY IN HIGH-POWER MEDIUM-WAVE OPERATIONS Cover image: Thinkstock/zhengzaishuru Radio World International Edition | December 2018 3 Ben A Chat With Dawson Ben Dawson Ben Dawson is former managing partner of specialized electrical engineering firm Hatfield & Dawson Consulting Engineers LLC. He is now senior consultant to the firm. Radio World: What is the trend of electricity costs in your own market? Ben Dawson: The Pacific Northwest has among the lowest electricity rates in the world. But a clear picture of transmitters at high power levels are typically merely recent changes is available from the U.S. Energy Informa- in standby condition. At very high power levels such tion Administration (see image). as those seen in ITU Regions I and III, electricity costs and maintenance costs of older equipment can be high RW: Over time, what have been cost-effective measures to enough to allow amortization of new equipment in rel- save on electricity costs for MW TX sites? atively short periods. Ninety percent efficiency is very Dawson: At multiple tower sites, conversion to LED avia- attractive. In a few isolated situations, however, where tion lighting has actually been a non-trivial savings. Mod- power costs don’t enter into political decision making for ern solid-state transmitters also reduce air handling and government broadcasters, rather antique transmitting cooling costs as well as contributing to savings because equipment is still in service. Even early solid-state equip- of their efficiency characteristics, typically in the 90 per- ment may be replaced in much shorter time periods than cent range. was true of 1950s era tube-type equipment, because of the difficulty of obtaining early types of FETs and other RW: What gain in efficiency would drive organizations to components. invest in a major revamping or to replace an existing trans- mitter? RW: From the point of view of broadcasters, what are the Dawson: The few existing high-power non-solid-state pros and cons of solid-state and tube-type? Information about electrical cost trends is available from the website of the U.S. Energy Information Administration. Access the data here. SAVING MONEY IN HIGH-POWER MEDIUM-WAVE OPERATIONS Radio World International Edition | December 2018 4 Dawson: For new equipment purchase, there is no FCC rules in the U.S.). advantage to tube-type transmitters any longer, and they MDCL was, of course, first proposed for U.S. use (by are almost entirely being manufactured only for HF use. our firm) in remote areas of Alaska, where AC power costs can be very high due to the cost of air delivery of RW: What are the most promising technologies to reduce diesel fuel. The BBC white paper “WHP-333” discusses operating costs for 100 kW+ MW transmitters? the current state of that organization’s work on this Dawson: The most critical problem with high-power subject. (BBC refers to their technique as AMC, for AM medium-wave transmitters is module failure, which Companding.) occurs for a variety of reasons. Newer solid-state devices with better characteristics and operation of solid-state RW: What else should we know about lowering operational devices with more safety factor will probably increase costs for MW broadcasting? capital cost but reduce maintenance costs, which are Dawson: Once a facility has been optimized for lowest nontrivial for some solid-state transmitting equipment. utility costs, the most important operating procedure is to avoid deferred maintenance. RW: What role do Modulation Dependent Carrier Level In railroad and utility practice, for example, if opera- algorithms play in high-power MW facilities and what tion of a facility exhibits declining revenue that cannot changes might be coming in MDCL? be attributed to poor performance but is entirely based Dawson: MDCL is still somewhat controversial. There on external market factor changes, the owner is justi- are major broadcasters in the U.S. who do not employ it fied in reducing maintenance expenditures to a level because of a perception that it has an adverse effect on that just exceeds the amount where additional revenue outer regions of the coverage area. Others perceive no decline can be shown as a direct result of the mainte- such effects, and employ it extensively. I think it’s a “red nance reduction. herring.” Essentially, this procedure allows the decision to ter- Use of MDCL in the “BBC” version — full carrier with minate the facility operation to be deferred so long as it no modulation, reduction of carrier with modulation up has marginal utility revenue potential. This can be effec- to ~6 dB — does reduce stress on antenna systems and tive in maintaining work force or facilities that would components thereof. One client we’re aware of uses it at otherwise not be cost effective. a 5 kW station for exactly this purpose, even though it If maintenance is deferred, however, a decision to doesn’t provide a significant operating cost savings. eliminate the facility is itself deferred, not avoided Use of MDCL can actually allow operation with higher entirely. Further, railroad and utility practice is to con- carrier power without exceeding amplifier device stress, sider that the “make-up” for such deferred maintenance although this may not actually be employed by any is always more costly than the deferred cost itself, even operating stations (and would not be consistent with discounting the cost of capital and any inflation. n It’s All About Efficiency with high-level plate modulation. Overall transmitter efficiency approximately 30 to 40 percent. Asked to identify the best ways to reduce 100 kW+ MW • 1960s to 1980s: Vacuum-tube RF power amplifiers transmitters operating costs, with Doherty, AmpliPhase, Pulse Duration Mod- consultant Geoffrey Menden- ulation (PDM) or Pulse Step Modulation (PSM). hall of Mendenhall Engineering Overall transmitter efficiency approximately 50 to replied: “High efficiency, Class D, 70 percent. solid RF amplification technol- ogy combined with high effi- • 1990s to present: Solid-state RF power amplifiers ciency, digital modulation tech- with PDM modulation or direct digital synthesis nology that utilizes Modulation (DX) modulation. Overall transmitter efficiency Dependent Carrier Level control.” approximately 80 to 88% He also provided this rough timeline of the historical progression of AM transmitter technology: • Add MDCL and further reduce power consumption by 25 to 35 percent depending on program material • 1920s to 1960s: Vacuum-tube RF power amplifiers and audio processing. SAVING MONEY IN HIGH-POWER MEDIUM-WAVE OPERATIONS Radio World International Edition | December 2018 5 Kelly: Modern Designs Make a Huge Difference A view from the manufacturer’s perspective Chuck Kelly, regional sales manager, Asia/ Chuck Kelly RW: What are the most promising technol- Pacific, for Nautel Ltd., says that costs for ogies to reduce 100 kW+ MW transmitters electrical energy have risen by an average operating costs? of 24 percent in the past 10 years in the U.S., Kelly: DSP-controlled modulation tech- and that most other countries have followed niques allow huge improvements in overall a similar trend, driven in part by increasing transmitter efficiency, such as precise consumption and increasing costs for fossil control of FET switching in the modulators fuels. We pursued the topic with him. and RF amplifiers. This means that the FETs are switched when the device is at a zero RW: In the past, what have been the most voltage point, eliminating capacitive losses.