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Turn Off the Stereo and See What Happens

The benefits of mono on FM are worth considering

A series of commentaries has explored the question of whether certain FM stations would do better to broadcast in mono than stereo. 

I’ve got a customer who has a daytime AM and a fill-in FM translator. The old owner was an engineer and wisely decided to just run the translator in mono. Yes, mono. This station airs oldies, high school sports and public affairs programming, but it’s mostly music.

So why mono? Well, this translator is on a derelict TV tower — he was smart about that, too — and the current CP is 220 meters AGL. With about 200 watts, he’s covering all of his home county and parts of four others. So you can get it in a car better than a 3 kW Class A at reference height (100 meters). 

But a lot of the coverage needed is pretty far from the transmitter site. He’s not blocked by terrain so much, it’s just distance. 

With stereo, that means noise in the fringe area. Without stereo, you can get it without noticeable noise a lot further out. So he turned off the stereo. 

This is a psychoacoustic fact about radio. Noise equals “Gee, what else is on?”

Real-world questions

The audience research people tell us about 70 percent of OTA listening is currently in vehicles. People don’t listen to radio much if there are other people in the car. They talk instead. If the radio is on, they don’t pay much attention. If they’re alone, they are driving the car. That means they are sitting on one side of the vehicle, and getting a stereo image when you’re stuck closer to one speaker than the other is pretty much impossible in my car. 

If there is a balance control of some kind, maybe you could tweak it, but how many people actually do things like that? 

Then there are smart speakers. Even if I listen to a stereo stream on my smart speaker, I only get mono because there’s only one speaker. Are there stereo smart speakers? I haven’t seen one.

So the only real listening environments where the presence of robust stereo separation might matter are when listening with headphones to a tuner in your home or to a stream app on your phone or laptop. 

How many people consume local radio that way? In my family, the only person I know who has a radio tuner in their home is me. Well, I’m a radio nerd, so that makes sense. 

I’ve seen people with earbuds doing something with their phones at the airport. Are they listening to radio?

FM stereo was a clever marketing tool the industry used to sell FM at a time when almost no one even had an FM radio. Then pop and country programmers discovered FM, and the rest is history.

If you’ve got a 100 kW blowtorch at 600 meters, it probably doesn’t matter. Those of us who aren’t so mighty and powerful would do well to try just turning off the stereo, not telling anyone, and seeing what happens next. It’s working for my customer.

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