Letters: AM, CMFE, More
     

Know Thy Audience

Regarding “CMFE Emphasizes Need for Diversity” (radioworld.com, keyword CMFE):

Interesting event. Good to see positive developments such as low-power DAB trials. A key issue for community media is measuring and understanding its audience. Not many do that — both listeners and target audiences. Developing programming, delivery formats and community-building activities to remain relevant and indeed even grow its audience in a fast-evolving media landscape.

John Goslino
Principal Consultant
Audience Dialogue
Australia

Null News Is Good News

In response to “The FCC Lays Out Its AM Plan,” Dec. 4:

Are there ever cases where the deep null should be aimed a bit to one side of the protected station to have the null optimized for where the listeners are, as opposed to where the station is? The example might have protected Station 1 with a unidirectional pattern aimed towards their metro audience. So Station 2’s null should be aimed at the metro audience, not at Station 1’s transmitter.

Jeffrey Harvey
Airborne Military Communications
Fall River, Nova Scotia

Riddle Me This, Fellow Techies

I was just thinking about AM and how to maintain the “analogue” (using old-school spelling) and adding a digital signal.

I starting thinking back to when I had a Hallicrafters receiver next to my bed. My dad, K0HMZ, had gotten it from my Uncle Kenny, who worked at Hallicrafters. It wasn’t an SX-99 but the next model up, a silver box.

Anyway I started playing around with the upper and lower sideband control on regular AM stations, and noticed that in the upper mode, I was still receiving the analog signal.

Could we modulate the upper sideband analog, with regular programming, and modulate the lower sideband with 140–160 kbps digital? Would a standard AM receiver still operate as normal, and our new digital receiver operate perfectly on the lower sideband alone?

Suppressing the carrier might not be necessary.

What do you think?

Steve Kafka
President
Continental Media Group
Phoenix

Comment on the above or any letter. Write to radioworld@nbmedia.com with “Letter to the Editor” in the subject line.


Rating People: 0   Average Rating:     
Comment List:

"...modulate the lower sideband with 140–160 kbps digital? Would a standard AM receiver still operate as normal?" A legacy AM receiver detects both sidebands. So any 'noise' (data) in the lower sideband would be audible along with the desired audio in the upper sideband. In theory, one could tighten the IF filter to eliminate the lower sideband, but in practice that's not going to happen for millions and millions of legacy receivers. Perhaps there's something in the concept where a differential data signal could be applied to both sidebands (opposite polarity in each of the two sidebands, thus cancelling out in the AM receiver), and the more modern receivers would be designed to detect the data signal in the difference. Even this would probably lead to noise in some receivers.
By J Harvey on 2/13/2014

Post your comment

Your Name:  Required
Your Mail:       Your email will not be published.
Your Site:    

max. 800 characters


Posts are reviewed before publication, typically the next business morning. Radio World encourages multiple viewpoints, though a post will be blocked if it contains abusive language, or is repetitive or spam. Thank you for commenting!