With the current state of the economy (in general) and the state of the broadcast economy (in particular) it makes sense to help any radio station cut down on its operating expenses. Thanks to a recent action by the Federal Communications Commission, there is now a way to help reduce the power bills for large AM stations (20kW and greater). It's called Modulation Dependent Carrier Level (MDCL).

MDCL is really a generic acronym that covers the three methodologies: dynamic amplitude modulation (DAM), dynamic carrier control (DCC), and amplitude modulation companding (AMC). The purpose of each of these technologies is to improve the overall efficiency of large AM transmitters, thus reducing the expense associated with power. A 30 percent reduction in power use expense is a realistic expectation.

These technologies were developed in Europe and have effectively made their way stateside because the FCC is now willing to grant waivers to section 73.1560 for stations that wish to implement MDCL. I'll cover a little about each of the three methods, what the expected results are, and how to implement MDCL at your station.

Let's first review amplitude modulation. Remember that at 100 percent modulation, the total amount of power in the upper and lower sidebands is 50 percent of the carrier power. So, for example, with a 50kW carrier, 25kW of power is radiated (along with the 50kW carrier) at the 100 percent modulation level. We're accustomed to a linear function that describes the relationship between the audio level and the percentage of modulation.

Out in the field, at each receiver, again we're accustomed to a linear function that describes the audio level obtained based on the modulation percentage of the received carrier. Additionally, the amount of quieting that a receiver will produce is dependent upon the carrier level that is encountered.

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