Radio engineers continue to experiment with modulation-dependent carrier level in hopes of saving money on AM transmitter power bills.
Cris Alexander, director of engineering at Crawford Broadcasting and a Radio World contributor, provides an update in his latest engineering newsletter. Since deploying MDCL on three high-power AM stations, he reports, “we have been seeing some very tangible savings, both in power consumed and cost.”
“It wasn’t until early February that we got our first look at the savings realized from MDCL operation from the [Nautel] XL60 at WXJC in Birmingham,” he wrote. “Astoundingly, we saw almost a 40% savings for the month of January over the same period last year. That is almost double the savings that we have seen on our two NX50 MDCL stations, and I really don’t see how MDCL alone can account for it.”
He initially suspected that weather had played a part, but after looking at temperature records he discounts that. “We’re going to have to watch this one over a longer period of time to determine what the real savings are.”
But Cris said his other two 50 kW stations with MDCL “are enjoying a consistent 21% reduction in power usage, and I believe that is a reasonable number that we can continue to expect in the cooler weather months. I look for increased savings in the cooling season, probably another 2-3%.”
Crawford also implemented MDCL on 5 kW WYDE(AM) in Birmingham. In January, compared to a year earlier, he reports a 5% savings. "This is a little less than I thought we would see, but I believe it is reasonable. At the lower power levels, the fixed loads (HVAC, rack equipment, security lighting, etc.) represent a larger part of the overall usage.”
He has filed a request to put MDCL on the air at KLZ(AM) in Denver. “With a simple firmware upgrade in the AM-IBOC exciter, we can experiment with MDCL on that station as well. It may not be worthwhile in the final analysis, but it’s certainly worth a look at least.”
Thanks, Cris, for sharing your findings. MDCL is a topic of great interest to many AM stations, and will be a focus of discussion at next month's NAB Show. I encourage stations to pass along their own experiences for sharing. Write to me at firstname.lastname@example.org.