Los Angeles engineer Mike Tosch spotted Radio World’s recent story about MDCL technology being used at WOR(AM) in New York, and shared his own experiences. Here’s his letter.
KSPN-AM710 in Los Angeles (DA2-50k ND Day/10k DA Nite-3 tower) is running MDCL full-time on our Nautel NX50 using AMC mode since early December 2011. We were able to do this simply on the NX50 by selecting the desired MDCL scheme and just enabling it. It is built into the NX50 “out of the box.” KSPN no longer runs AM IBOC and runs full 125% positive peak, full NRSC modulation.
We elected to use the AMC scheme first at the suggestion of Tim Hardy, DOE at Nautel. The Nautel NX50 does not require any upgrades or Nautel personnel to be on site to invoke this system. I was even told by Gary Warner in Nautel Customer Service, “As for stress on the transmitter, it’s actually less stressful.” This was of interest to me as I did not want to make the transmitter work harder to achieve the results. Gary went to explain the AMC scheme: “With AMC, as modulation goes up, power goes down. With no modulation, the power will be as per the preset. With 100% mod, the power drops 3 dB.”
We intend to analyze our electric bills once one full billing cycle with LA-DWP has passed. This will be compared to last year’s bill for December and we will see how the savings looks. We spend about $65K/yr on electricity costs for the whole site (includes HVAC, etc). The transmitter meter now usually sits at about 28 kW (day) with jumps higher with modulation.
In listening tests and talking to several different folks, both engineers and non-engineers, no one has noticed any changes to audio levels or modulation density, quality or basically anything. I did listening tests at night in usual places and could not discern any difference in audio quality or loudness. PPM decoders are all operating fine at transmitter and studio with no glitches at all. We would be interested in any additional studies performed on actual PPM units carried by the public. At present, we do not have access to any of the actual PPM units.
We are thankful that the FCC has allowed this technology to be used on U.S. AM stations as it will help with our engineering budget and hopefully extending the useful life of the transmitter.
Mike Tosch, CSRE, CBNT, W6UWB, is chief engineer for KSPN(AM) in Los Angeles. Comments do not necessarily represent those of his employer. Email firstname.lastname@example.org. Radio World welcomes your experiences with MDCL; write to email@example.com.