Stations Begin Exploring Power-Saving MDCL

KCBC is an early U.S. adopter; WOR eyes impact on PPM and HD
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How much money will AM stations save thanks to MDCL?

Engineers are beginning to explore the possibilities now that the FCC is granting Modulation-Dependent Carrier Level waiver requests. As we’ve reported, advocates hope the new commission policy will help AMs save a lot of money on power bills.

Crawford Broadcasting now has received notice that the commission granted its request for station KCBC, and has been told the San Francisco AM was the first in the country to apply for a waiver. It airs at 770 kHz, with 50 kW power daytime and 4.1 kW night.

“We intend to begin employing MDCL in the next few days and evaluating its effect on the recovered audio at various locations, its effect on HD Radio performance and its benefit in terms of power consumption,” Crawford Director of Engineering Cris Alexander said. He is also an RW contributor.

“KCBC uses a Nautel NX50 transmitter, which includes the MDCL option as part of its standard feature set. Both the DAM and AMC methods of dynamic carrier control are supported. We intend to test both methods but will probably begin with AMC, since that method will produce little or no noise floor raising receiver AGC action during periods of low modulation. We anticipate employing 4 dB of dynamic carrier control as a starting point.”

Alexander said that as MDCL operation begins, “we will solicit reports from certain listeners, particularly broadcast engineers, in the Bay Area. We are looking for any perceived degradation of audio quality in the analog domain and for any reduced coverage or robustness in the digital domain. We will also be watching power consumption closely to determine whether the claimed savings will be realized.”

Elsewhere, WOR(AM) in New York — 50 kW both day and night, at 710 — has agreed to test the system Harris makes available for its transmitters. Buckley Broadcasting VP and Corporate Director of Engineering Tom Ray told RW, “We will be testing both methods for HD Radio compatibility, but more importantly, we will be engaging Arbitron to see if there is any effect on recovered PPM data, as dynamically changing the carrier level will have an effect on the AGC in receivers, which does have the potential to corrupt the PPM data stream in the recovered audio.

“Additionally, it will be interesting to see if there is any impact on the reception of WOR driving among the buildings in Manhattan. If this works out, WOR looks forward to the potential cost savings for transmitter operation.” Ray too is an RW contributor.

Share your own experiences with these power-saving technologies. Write to radioworld@nbmedia.com.

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