What's Causing Your Radio Interference? Something Called 'Ducting'
You're not alone. We heard from audience members asking what this is and why this has been happening recently. WHRV's senior engineer, Ray Lenz, spoke with Morning Edition host Gina Gambony with answers.
On what the heck is going on
We're hearing WSCL-FM all the way from Salisbury, Md. They are on the north end of the Chesapeake Bay. They're on 89.5 frequency, and from time to time their signal shows up down here in Hampton Roads. So what's happening is called ducting. Call it tropospheric ducting, ducting or 'tropo' -- it's when a layer of warm air gets trapped between the cool air that's close to the water and the cool air that's close to outer space.
Like a hot air sandwich
Yes, it's like a good, warm scrambled egg sandwich. And this effect makes a radio signal travel all the way from Maryland down here.
And here's how it happens: When the signal gets to the boundary between the cool air and the warm air, the signal bends. Then when it gets to the boundary below -- where the warm air meets the cooler again -- the signal bends up again. This layer of warm air guides the signal all the way down to us, sometimes strong enough to override the WHRV signal.
To everything (turn, turn, turn) there is a season
While it can happen any time of year, it usually is most noticeable in spring, summer and fall. I have noticed it more frequently in the morning when the water is still cold, and the air hasn't had a chance to warm up yet. But it can last for several hours, and it can last through the whole day, all depending on the weather conditions.
Ducting can cause WHRV to be heard in other parts of the country, too. We have had reports from people who are listening in Wisconsin and in New England that they've heard our signals up there. And there's not too much that we can do about this scientific phenomenon. Generally, you just have to be patient and wait for those boundaries of cold and warm air to dissipate for the ducting effect to go away.