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Radio Broadcast Technical Consulting and Sales
 10032 Island Drive, Brainerd, MN  56401

 

Engineer's Log of Mark W. Persons
HD FM Radio Tested
June 21, 2009:  When at dinner with Mark Persons at the Black Bear Restaurant in Brainerd, MN, John Kean from National Public Radio in Washington, DC, explained his method for measuring "real world" interference to adjacent channels on the FM broadcast band when elevated levels of digital carriers are added to an existing HD station.  John took issue with a recent study done by Ibiquity regarding the potential HD interference to existing analog FM broadcast stations.  His study will assess the impact to listeners of existing analog FM radio stations from increasing the digital power by as much as 10 dB.

He planned testing this time was between KCRB Radio 88.5 MHz at Bemidji, MN, and KBPR Radio at 88.3 MHz, at Brainerd, MN. 

The radio broadcast engineering eyes of the nation and the world were focused on this test.  

(l-r) John and Jan Andrews are looking at an Anritsu RF spectrum analyzer alongside the Agilent N9340B RF Spectrum Analyzer from M. W. Persons making sure the KBPN signal complied with FCC rules. 

Glynn Walden, Vice President of Engineering for CBS Radio in Philadelphia, PA, was on hand to check modulation with a new Belar HD modulation monitor.
John and Jan show off the omni-directional antenna created by Kintronic Labs for monitoring KBPN FM signal in the fringe area.  This antenna mounts to a luggage/ski carrier on top of any car.  The procedure involved driving a pre-planned course, on a road at 40 miles per hour, for about 80 seconds while listening to a male voice, a female voice, and two different kinds of music.  The recorded audio will be submitted to an audience, which will grade the audio for listen-ability when varying levels of HD digital signal are broadcast by the adjacent channel station.             
June 22 and 23, 2009:  Here is Mark Persons at KBPR Radio, Brainerd, MN, the victim analog station, running the station with pre-planned audio from a CD player.  It all happened between midnight and 4:30 AM.  Everyone went back home or to a motel very sleepy after the experience. 

November 6, 2009:  National Public Radio and Ibiquity reached an agreement to allow a 6 dB power increase for HD modulation on analog FM carriers.  Details 

By the way, HD stands for Hybrid Digital, not High Definition.  HD is a way of combining analog and digital modulation on one radio channel.          

The stories go on and on.  Stop in again sometime.  I'll leave the soldering iron on for you. 
Mark W. Persons   Ham WØMH

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page last edited 12/12/2009