Sitting in my office today I had my radio on as usual. It's down low so I didn't notice the slight amount of static in the signal. That's weird. It should be perfect in my office.

What tipped me off to it was a message we received on Facebook from someone in Madison who said they normally get our station in just fine, as they should, but today they couldn't get it.

Sometimes our stations will be affected by birds that perch themselves on the slotted microwave dishes that our audio signal is sent or received on. This causes a garbled sound or cuts the audio completely. But this was not birds. The signal is weak and has static.

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I checked with our engineer to make sure we weren't on the backup transmitter for some maintenance reason. That has a fraction of the power our 100,000-watt station has. We weren't on the backup.

"Getting some atmospheric skip," he replied to my text. It's a phenomenon I had forgotten about.

The technical term for it is sporadic E propagation. I know it's a thing that happens in the summer that causes signals to be weak close to where they should be well received, and come in great at some crazy distances away from where they were transmitted. It is caused by weather and other atmospheric conditions.

The easiest way to translate the science I don't really understand is that radio and TV signals are bounced back off the ionosphere and can come back down hundreds or even thousands of miles away.

Today, July 21, 2021, there is a strong area of this between Sioux Falls and Pierre, according to the map from, signals are capable of skipping up to 300 miles. Pierre is about 188 miles from Sioux Falls. Signals that are normally not capable of being heard much farther from Pierre than Chamberlain are able to enter the area and interfere with stations based in Sioux Falls.

For a couple of months, a letter has been sitting on my desk from a distant TV and radio hobbyist in western New York. He sent us a letter in the mail saying that he wanted to confirm that what he heard on his equipment in the town of Holley. Measured on Google Maps, that's 956 miles from our transmitter.

The man sent a photo of his radio displaying the RDS (text you see in your car radio) that said 104.7 FM, KKLS, Deja Vu by Olivia Rodrigo. The letter said this was played at 1:11 PM on May 20, 2021. I looked back in our music software to see if that was the case. It was, with the exception that on my log the song started at 1:13:08 pm.

Andy Erickson/TSM
Andy Erickson/TSM

So if you hear weird stuff on the radio in the summer, now you know why. Sporadic E-Skip is the culprit.


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