Moody Bible Institute’s 90.1 WMBI(FM) in Chicago is currently operating at 10 kW transmitter power output due to interference with communication equipment at nearby Chicago O’Hare International Airport.
The issue stems back to November. The station went off the air completely after being notified by the FCC that the Federal Aviation Administration detected an “aspect” of its 90.1 FM signal causing minor interference with local air traffic control.
The flagship station of the Moody Radio network, WMBI is a grandfathered Class B station that ordinarily operates with 100 kW ERP. WMBI’s transmitter site, located off Army Trail Blvd. in Addison, Ill., is approximately five miles southwest of O’Hare.
In a reduced power notification filing with the FCC on Dec. 10, Moody said that the FAA recently introduced communications that are highly sensitive to background noise.
As a result of the new communications equipment, WMBI must filter out spurs as low as –80 dB at 133 MHz, Moody wrote in its FCC filing.
WMBI’s equipment is within specification thresholds, Moody wrote, but it was still causing interference with the FAA on its new communication channels.
In the filing, Moody said that it has been able to filter WMBI’s exciter output, but it is only able to make use of approximately 10 kW of its licensed 35 kW TPO.
Moody said that with the busy holiday travel season, it desires to wait until January before moving forward, as it has spent “considerable time” getting to this point. It has price quotes for full transmitter power output filters and is “considering all options.”
WMBI requested special temporary authority to operate at the 10 kW TPO through March 1.
November FCC notification
On Nov. 17, Moody Radio announced on its Facebook page that the Chicagoland signal went off the air due to unexpected technical issues.
Three days later, Wes Ward, Moody Global Media’s vice president, posted that the station was notified by the FCC after the FAA detected the air traffic control interference.
“Out of an abundance of caution, we temporarily paused broadcasting via our 90.1 FM signal due to their request,” Ward wrote.
Moody said that WMBI’s transmitter was operating normally, within required thresholds.
“It appears that recent changes in system sensitivity on the FAA’s receiving side have made it easier for portions of nearby FM signals — including Moody Radio — to be detected,” Ward wrote.
Ward wrote that other radio stations throughout the U.S. have encountered similar issues and are also making adjustments.
After both testing on WMBI’s end and work by engineers from the FAA and FCC, WMBI is confident it has identified a permanent solution, Ward wrote.
When reached by Radio World, a Moody spokesperson said that due to its ongoing work with federal agencies, it would have more to say on the matter at a later date.
Radio World has also reached out to the FAA for further comment.
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