Mysteriously malfunctioning garage doors

About ten days ago, a mysterious radio signal around Ottawa, Canada began blocking the operation of hundreds of garage door openers. (Background here.) On Thursday, the garage doors began working again. From CBC News:
The powerful radio signal causing the problem stopped transmitting on Thursday afternoon, around the time CBC News contacted the U.S. Embassy to ask if it knew anything about it.

The embassy categorically denies that it had anything to do with it.

The signal was being transmitted at 390 megahertz, a U.S. military frequency used by the Pentagon's new Land Mobile Radio System. The same frequency is used by garage doors openers, which started to malfunction around the city about almost two weeks ago. A similar problem has popped up around military bases in the States.
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