On January 29, 2010, the Federal Communications Commission (FCC or Commission) released an Order that permits most FM radio stations to increase digital power from the current maximum of one percent of authorized analog power up to a maximum of ten percent of authorized analog power. With the exception of "super-powered" stations (those stations operating with parameters in excess of class maximums), all FM stations can increase digital power by 6 dB anytime after the effective date of the Order by giving the FCC notice within ten days of such power increase. Stations that desire to increase digital power beyond 6 dB, to up to 10 dB, must receive permission from the FCC through an informal application. This application must demonstrate that such power increase will not cause interference to analog stations through a formula established in the Order. Finally, the Order creates interference mitigation and remediation procedures to resolve complaints of interference to analog stations from digital stations. A copy of the Order is available here.

Power Increase

The FCC currently permits FM stations to operate digitally with an effective radiated power (ERP) of one percent of a station's analog ERP (also known as 20 decibels below carrier (-20 dBc)). In the Order, the FCC allows FM stations, except "super-powered" stations, to increase digital power up to 6 dB (from -20 dBc to -14 dBc), which amounts to a four-fold power increase. Stations can commence such power increase anytime on or after the effective date of the Order. [1] Within ten days of implementing a digital power increase, stations must electronically notify the Media Bureau. Any eligible FM station that desires to increase digital power prior to the effective date of the Order, can file a request for Special Temporary Authority (STA) to do so.

The only category of FM stations that may not automatically increase digital power is "super-powered" stations. For the purpose of the Order, the FCC defines a "super-powered" station as a station (i) that has an ERP in excess of the maximum permitted for its class, or (ii) with authorized facilities that produce a reference contour that exceeds the pertinent maximum contour distance as defined in Section 73.211 of the FCC's Rules.

To determine if an FM station is a "super-powered" station, the Media Bureau will provide an FM Super-Powered Maximum Digital ERP Calculator (the "Calculator") on the Bureau's Audio Division web page (http://www.fcc.gov/mb/audio/digitalFMpower.html). The Calculator will compare a station's reference contour with the appropriate class contour to determine if the station is a super-powered FM station. If it is, the Calculator will then determine maximum permissible digital ERP for the station. [2] The licensee of a super-powered FM station must then file an informal request for an increase in the station's digital ERP.

The Order also establishes procedures for FM stations to increase digital power to up to 10 dB (from -20 dBc to -10 dBc), which is ten percent of analog power. To do so, an FM station must demonstrate that such a power increase will not interfere with first-adjacent analog stations pursuant to an interference formula established in the Order. The formula is based on the field strength of the "interfering" FM station's analog signal along the protected 60 dBu analog service contour of a potentially affected first-adjacent channel FM station. [3] Here is how the formula works:

The licensee of a digital station desiring to increase digital ERP in excess of -14 dBc must first calculate its station's analog F(50,10) field strength at all points on the protected 60 dBu F(50,50) contour of a potentially affected first-adjacent channel analog FM station. Once the most restrictive analog F(50,10) field strength of the proponent station has been determined, the licensee will use the following table to determine the proponent station's maximum permissible digital ERP:  

Click here to view table.

After a licensee has determined its permissible digital ERP, it must file an informal request with the Media Bureau.

Interference Procedures

The Order establishes an interference complaint process under which the Media Bureau will consider verifiable listener complaints of interference from within the protected contour of the FM analog station receiving interference. [5] The new procedures first require the stations involved to work cooperatively to confirm the instances of interference and to attempt to eliminate the interference using voluntary tiered digital ERP reductions (i.e., progressive reductions in power until interference is eliminated). If the stations fail to reach agreement on appropriate interference remediation measures, the licensee of the affected analog FM station may file an interference complaint with the Media Bureau. The Media Bureau, however, will investigate a complaint only if it includes six reports of ongoing (not transitory) objectionable interference. [6]

The Order specifies that the Media Bureau will review a complaint and order appropriate action within 90 days of the date on which a complete and sufficient complaint has been filed. If the Media Bureau fails to act within the allowable 90-day period, the interfering station must immediately reduce its digital ERP as follows:

  • Stations operating with digital ERP in excess of -14 dBc must reduce digital ERP to -14 dBc. If ongoing complaints of objectionable interference persist, the Media Bureau may require subsequent 3 dB reductions in digital ERP to -17 dBc and -20 dBc, until it acts on the pending interference complaint.
  • Stations operating with digital ERP of -14 dBc or less must reduce digital ERP to -17 dBc. If interference complaints persist after this reduction, the Media Bureau will order the station to reduce digital ERP to the currently permitted maximum of -20 dBc and require it to remain at that level until the Media Bureau acts on the pending FM digital interference complaint.