interference to FAA frequencies

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.
Continue Reading FCC Notes Violations for Two LPFM Operators for Spurious Emissions – Make Sure that Your Station is Transmitting Only Within Its Assigned Frequency

In 2006, the FAA proposed requiring that many communications users seek FAA No Hazard Determinations not only before they make changes in the height of a tower, but also prior to frequency or power changes.  The FAA sought to review applications to determine if proposals would create any interference to frequencies used by the by aircraft and by the FAA for air navigation purposes. This review would be in addition to any review that the FCC made of interference considerations.  Many communications companies and engineering firms argued that this second layer of frequency review was unnecessary; and certain engineering groups contended that the FAA’s interference programs were not accurate – finding interference where none existed.  After over 4 years of consideration,the FAA has now decided that most of the frequency blocks that it was considering did not really pose a threat to air navigation, with one exception.  The FAA determined that interference problems do arise from FM operations, and thus the FAA did not dismiss their proposal to require its approval of FM changes – even where no tower height changes are planned.

The FAA, however, apparently will not be making this decision alone.  Instead, that FAA is coordinating with the FCC and NTIA (an Administration in the Commerce Department that coordinates between various government agencies that use spectrum) to adopt policies that will govern the potential for interference from FM stations to FAA operations.   The FAA’s Notice says that more information about what is to be proposed for FM stations should be forthcoming soon.  This can be a real issue for FM stations, especially ones proposing significant power increases or frequency changes in congested metropolitan areas with numerous public, private and military airfields in the vicinity. 


Continue Reading FAA Working On Proposals to Require FAA Coordination For FM Changes Even Where There is No Change in Tower Height – Rejects That Requirement for Other Services