Probably because of Tropospheric Ducting over Lake Erie. Tropospheric Ducting is the propagation of radio signals above 30 mHz, via bending and ducting along weather fronts in the lowest layer of the Earth's atmosphere, the troposphere. Signals don't bounce and are not reflected. It's more like they are "bent." Cold air is more dense than warm air, so it has a higher refractive index. Normally, in the first 5000 feet of the Earth's atmosphere, cold air sinks and warmer air rises. The opposite of that is called a "temperature inversion" where the warm air is trapped below a layer of colder air. Radio signals are guided through the boundary between the two layers like air through a "duct." In our area, this usually happens over Lake Erie in the summer when it is warm and humid near the ground and a weather front approaches a high pressure area. This will affect FM signals that are on the same channel and are located near the lakeshore on opposite sides of the lake.

The stations most affected here in the Cleveland area are WJCU at 88.7, WCSB (since April of 2007) at 89.3, WZAK at 93.1 and WGAR at 99.5.

The corresponding stations across the lake from us are CIMX at 88.7 in Windsor/Detroit with 100,000 watts, CKGW at 89.3 in Chatham/Kent, Ontario with 16,700 watts, WDRQ at 93.1 in Detroit with 26,500 watts and WYCD in Detroit at 99.5 with 17,500 watts. CKGW is a new, legitimate station that went on the air on April 4th, 2007 at 89.3 from Chatham-Kent, Ontario.

Interestingly, the ducting is a bi-directional process so we are also interfering with them at the same time they are interfering with us. (although we may notice it closer-in to the station due to our lower power) You will notice that when the weather changes, usually the ducting will stop as abruptly as it began.

Since the ducting happens at higher frequencies as well, it can be seen on some weather radars as additional "ground clutter". In severe cases, you can see the entire Canadian shoreline of the lake outlined on the radar!

Another way to know that the "Tropo" is "in" is to monitor FM channels that have only a Canadian or Detroit signal on them. Some examples are 93.9 FM "The River" from the Windsor/Detroit area, 95.9 "FM96" from London, Ontario and 101.1 WRIF from Detroit.

When the ducting is taking place, these stations will usually come in much more clearly than normal.]
What can I do to minimize the interference? If listening at home, you can use a directional antenna (such as a rooftop TV/FM antenna) pointed towards Downtown Cleveland. If the direction you need to point the antenna for WCSB is significantly different than the interfering signal coming from Chatham/Kent, Ontario, this should help.

If mobile, there's not much you can do other than to drive closer to downtown to receive a stronger signal from WCSB.
Please note that we have 2 full-time Internet streams available at www.wcsb.org so you can listen on the computer or on your smartphone.

Mark Manolio
WCSB Engineer