In two Notices of Violation issued on one day this week, an FCC Field Office cited Low Power FM operators for using transmission systems that, in addition to transmitting signals on their authorized channels, were also emitting signals on other channels that posed the potential for interference with other users on those other frequencies – sometimes not even broadcast frequencies. In one case, the FCC noted that it was the FAA that reported the interference (the other notice released the same day is available here).
All broadcast transmissions have the potential for these spurious emissions on channels other than the ones for which a station is authorized, especially if a station is near other stations as frequencies can interact to produce these unintended emissions. When constructing and operating any broadcast station, care should be given to ensure that these off-channel emissions are not of a signal strength beyond that permitted by the FCC rules as interference can occur and the FCC can potentially impose fines.
Neither of these Notices proposes a fine. Instead, each asks for a response from the operator of the LPFM station and reserves the right to impose a fine depending on the response and any corrective action that is taken. The FCC does not often publish these routine Notices of Violation in its Daily Digest of important actions from the Commission, as it did with these two notices. This publication may be meant as a warning to all stations to ensure that their transmissions are within the permitted limits to avoid any enforcement action. So consider yourself warned!