At the end of September, Jeff Littlejohn, senior VP of engineering for Clear Channel, distributed a memo to the Clear Channel station engineers. That memo has created more industry buzz and prompted more people to send us letters than anything I can remember in the past seven years since I have been the editor of Radio magazine.
The memo outlines Littlejohn's directive for all Clear Channel AM stations to reduce their audio bandwidth to 5kHz for talk formats and 6kHz for music formats. The decision was based on several factors, but there are three strong reasons: most AM radio receivers cannot produce audio frequencies above 4.5kHz, it will improve modulation efficiency and it will reduce interference to first-adjacent channels.
Littlejohn is also the co-chairman of the NRSC's AM subcommittee, and in his memo he stated that he would propose this standard practice among all AM licensees.
A few days later, Cris Alexander, director of engineering of Crawford Broadcasting, told Radio magazine that the Crawford stations had also examined the benefits of reducing the AM audio bandwidth, and that the Crawford stations would follow suit and reduce their audio bandwidths to 5kHz.
It didn't take long for the letters to pour in. The e-mail list servers filled with chatter. The subject was repeatedly brought up on the floor of the NAB Radio Show. Some of the chatter on the e-mail lists was outright mean with personal character attacks on Littlejohn.
While the furor subsided by the end of the Radio Show, the issue itself is still on the minds of radio engineers. You can read some of the letters we received in this issue's Reader Feedback section.
Most of the letters we received opposed the decision. To be honest, I was not surprised to see this because the majority of letters on any topic typically come for those who oppose the topic. Those who support it tend to be quiet.
Littlejohn and Alexander noted that the decision was based on current analog systems, and that IBOC had nothing to do with the decision. Again, the opponents quickly state that the analog reduction will only help to make the IBOC signal sound naturally better. While it is true that a frequency-limited analog signal will sound dull compared to a fuller-bandwidth digital signal, it's a weak argument to use this as the sole point of opposition to the Clear Channel decision.
Can you summarily accept that there are no receivers capable of receiving anything above 7kHz? Of course not. There are radios that can cleanly receive wideband audio. Based on the research I have seen, there are only a few current designs that can do it. It's also difficult to determine how many older or AM stereo receivers there are still in use that have the wider bandwidth. In the end, you can't please all the people all the time.
The benefits to the overall spectrum efficiency make sense to me. Reduction of adjacent-channel interference and improved modulation efficiency are valid concerns.
I applaud the efforts of Littlejohn and Crawford for their willingness to make this change to better AM radio today, while still looking ahead to what radio broadcasting might be tomorrow.
Radio broadcasting is constantly challenged by other forms of media, and runs the risk of being left behind in the technology evolution. HD Radio is one form of digital transmission in the latest stages of development and earliest stages of rollout. DRM is being evaluated and implemented for medium-wave around the world. Cam-d is yet another digital AM system being developed.
If radio remains static it is destined to fail. It will be left behind as the listening audience turns to Ipods, podcasting, satellite radio and other forms of digital delivery.
You may not like what you see and hear with the current activity in analog and digital radio, but you can follow those who are making a new path, take an active part in clearing a different path or stay where you are and be left behind.
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