New  Equipment
Used Equipment
Our Office
What We Do
Web Links
Tech Tips
Engineer's Log
Contact Us

Radio Broadcast Technical Consulting and Sales
1032 Island Drive, Brainerd, MN  56401
Phone: 218.829.1326

Public Speaking

April 29, 2006

Mark Persons gave a talk on
IBOC/Digital Broadcasting/HD Radio

The speech was before the Minnesota News Network annual awards gathering of about 70 people at Maddens Resort near Brainerd. Minnesota.  Here are the notes, from the speech:
History teaches us that it is a good idea to know where we came from so we might know where we are going. 

In the beginning, there was AM(Amplitude Modulation) Radio.   It served well starting in the 1920�s and is still serving well in many communities, especially smaller ones, throughout the state.

Radio is paying our wages.  You can�t beat that.

FM(Frequency Modulation) was experimented with in the 1930�s by great people like Edwin Armstrong, a creative inventor whom my father knew.  Armstrong started the Yankee Network of FM stations on the east coast.  My father built the first FM station in Duluth in 1940.

As you know, FM has advantages over AM with less noise especially during thunderstorms.   Since no new broadcast transmitters or consumer receivers were build during World War Two, the early 1950�s was an obvious time to convert the AM broadcast band to frequency modulation.  However, it was not to be.   AM stayed what it was.

FM proponents persisted.  They sought and got a new band (88 to 108 MHz) late in the 1950�s.  In fact, my family held a construction permit to build a 100 Kilowatt FM station in Minneapolis in 1961 and let it drop because there was little interest in this new medium.  What would that be worth today?  Shows you how smart I am.  To be fair, a lot of money would have been spent to keep the frequency going until FM came of age in the late 1970�s.  There was a chance it would not take off at all, which is the case for many other technologies like Quadrafonic, FMX, and AM stereo just to name a few.

The radio broadcasting that we do today is called ANALOG to differentiate it from the DIGITAL that we may be doing tomorrow.

Radio, now there is a magic word.  I had a �Radio Flyer� wagon when I was a kid.  Did it have a radio in it?  NO, but it had the word Radio on the side.  It was a �buzz word.�

So, where did DIGITAL come from?  Well, with computers and music on the Internet, digital became the new �buzz word.�  Young people go into Best Buy and will purchase almost anything that has the magic �digital� word on the box.  I can see why some broadcasters might feel left out.  But, more correctly, it is probably manufacturers looking to sell equipment and Ibiquity looking to sell licenses that is pushing this revolution.

The obvious choice, when looking at history, was to have a �digital� band just like we have an AM  band and an FM band.  But, since the �digital cat� is already out of the bag any FCC window for filing would have been swamped by applications from every AM and FM broadcaster along with many average Joe�s on the street corner wanting a �voice� in this world. 

Clearly, this could not work.  So, what is left?  It was a compromise decision to run digital modulation on top of existing AM and FM analog modulation on radio stations. 

Is this possible?  Well, if you had asked me 7 years ago, I would have said NO.  However, some people, more clever than I, have devised a scheme where it IS possible IF you have enough money in your pockets to make it work. 

You will remember that ANALOG CELL PHONES worked quite well and suffered some noise problems, much as any broadcast station, when in fringe areas.  Nowadays, digital cell phones divide one previous analog channel into four or even 6 digital channels.  That is what digital broadcasting is capable of too.  However, cellular engineers were smart enough to realize that they could NOT put analog AND digital on one channel at the same time.  Even television has separate analog and digital channels.

Knowing that, doing ANALOG and DIGITAL modulation schemes simultaneously becomes a real balancing act for radio stations going digital.  In addition, making a radio station digital is not a one-time expense.  It is a lot like websites, maintenance is required.  Don�t plan on having the average engineer do repairs.  A spectrum analyzer is required and someone who knows how to run it.  You don�t find those people on every street corner.

Like cell phones, you do not get the range with digital that you got with analog.  In fact, right now you have listeners on your extreme fringes that listen because they like the audio you send them.  After digital arrives in your part of the AM or FM band and especially if you go digital, plan on loosing some fringe listeners.  The digital signal will add noise to analog reception and will make the fringe listener tune away because the noise level will be too high. 

Noise, did I say noise?  Well yes�you know what a dial-up computer modem sounds like when it is connecting to the Internet.  Think of that noise as being broadcast continuously by the digital station. Your analog signal needs to compete with it.  It is apparent in the analog coverage fringes.  Because the digital signal will not go as far as your analog signal goes now and the analog will not go as far because of the digital noise.   Plan on doing more �local� broadcasting.

Is all of this bad?  Well, it might keep some competitor signals out of your market.  The real plus for you is multicasting.  You can divide your digital signal into multiple audio streams.  Wow, now you need to come up with new program formats to send to listeners.   Niche Broadcasting.

What about audio quality?  Since it is digital, noise is not an issue where the signal is heard.  The quality is high when you broadcast just one audio stream.  As you divide it to broadcast more formats, the quality will suffer.  Many feel that analog FM sounds every bit as good as digital, if not better, when there is only one program channel.    As you divide digital, the quality diminishes, but it is likely that the vast majority of listeners will not hear the difference or even care.  Only a few will. 

You get to decide to jump in or not.  The FCC is not mandating digital.  You will probably wind up doing it just to get the extra multicasting channels.  We will see what the future brings.

back Back to the Office          back Back to "What We Do"

Questions?  Email Mark Persons:  teki@mwpersons.com 

    Return to Home Page 

page last edited 02/22/2016