AM Transmitter Power Reduction Algorithms

Power efficiency is an extremely important factor for broadcasters, both in dollars spent annually on energy consumption and the ever-growing need to be environmentally conscious.  Harris® Power Smart® technology continues to deliver energy-savings for broadcasters, and the company now extends Modulation Dependent Carrier Level (MDCL) power reduction algorithm technology to AM transmitter customers in the U.S.

Harris offers two distinct MDCL algorithms for its AM transmitters — Adaptive Carrier Control (ACC plus) and Amplitude Modulation Companding (AMC plus) — enabling broadcasters to choose the solution that best fits their individual needs.  These power-reducing algorithms have been used on Harris transmitters for international customers since 1993.

Why is This Now Being Introduced in the U.S.?
Recognizing the trend toward higher energy costs, the FCC delivered Public Notice DA 11-1535 on September 13, 2011. This notice acknowledges the benefits of algorithms (termed MDCL by the FCC) that are used to reduce AM carrier power under-modulation and the potential savings for broadcasters.  The significance of notice DA 11-1535 is that it allows the implementation, via waiver, of MDCL algorithms by U.S. broadcasters, enabling them to start saving significant dollars in energy costs.  AM licensees who wish to implement MDCL technology shall file with the Audio Division a letter requesting waiver of Section 73.1560(a) of the rules, addressed to:

MDCL Waivers
Federal Communications Commission
Audio Division, Media Bureau
445 12th Street SW, Room 2-B450
Washington, DC 20554

How Green Can Your Transmitters Be?
While the actual power savings is dependent upon the audio content and audio processing, real-world savings of up to 35 percent have been achieved, resulting in significant dollar savings for the broadcaster.

ACC plus and AMC plus both reduce AM carrier power as a function of modulation level, resulting in significant energy savings.  ACC plus reduces the carrier level during segments when audio modulation levels are low, while AMC plus reduces the carrier level during segments when modulation levels are high.  Determining which algorithm will work best for a particular broadcaster will be dependent on the format of the station (i.e., talk vs. music), the audio processing and personal preference.   Below are graphs showing how each algorithm reduces carrier power based on modulation level.  ACC plus can be set up to reduce power in 1dB steps from -1 to -6dB as modulation levels decrease, while AMC plus will reduce carrier power by 3dB at 100 percent modulation.

How Can I Take Advantage of ACC plus or AMC plus?
Either of these energy-saving algorithms can be implemented on Harris DAX™, DX® and 3DX® transmitters. AMC plus or ACC plus can be installed on existing transmitters operating in the field or can be factory-installed on new transmitter orders.  When upgrading an AM transmitter in the field, the upgrade kit will contain the necessary board assembly, instructions and software chips that allow the broadcaster to implement either energy-saving algorithm based on their preference.  To start saving significant dollars in your energy bill, contact your Harris salesperson today.

What about HD Radio™?
Initial tests have shown that MDCL technology, and in particular the ACC plus and AMC plus algorithms implemented by Harris, are compatible with hybrid IBOC transmission — including full compliance with the AM IBOC spectral mask requirements.  The National Radio Standards Systems Committee recently created a sub-committee to investigate the effects of these algorithms on the AM IBOC signal and receiver performance.  Testing with several types of receivers is underway, and the FCC will permit AM stations broadcasting in hybrid AM IBOC mode to implement these energy-saving algorithms, provided the AM IBOC signal continues to comply with the spectral emissions mask and that the relative level of the analog signal to the digital signal remains constant.

What if I Need Help?
For broadcasters unfamiliar with MDCL technology, unclear on how ACC plus and AMC plus work or with questions on how to upgrade an AM transmitter, Harris offers full on-site installation and setup in the continental U.S.   For upgrades and installation outside the continental U.S., please contact your Harris salesperson to obtain a quotation for a complete upgrade.  

Why Harris?

• ACC plus and AMC plus are proven ways to reduce energy consumption up to 35 percent, resulting in significant dollar savings
• Harris has a proven track record of success, providing ACC plus and AMC plus systems to international customers since 1993
• Optimum flexibility is provided in the implementation of MDCL algorithms with ACC plus and AMC plus
•  Harris DAX, DX and 3DX AM transmitters can be upgraded with either algorithm in the field or the technology can be factory-installed on new transmitters
• Harris continues to be intimately involved with testing on AM transmitters in the U.S. and with HD Radio compatibility testing