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The FCC has approved In-Band On-Channel (IBOC) digital radio operation for AM (daytime and nighttime) and FM broadcast stations.

Current Information for Licensees

  •  To obtain a list of stations authorized for "hybrid" operation (analog + digital signals), select one of the following links: [ AM | FM ].
  •  AM stations may apply to operate in digital-only mode.  See All-Digital AM Broadcasting, Revitalization of the AM Radio Service, Report and Order, FCC 20-154, 35 FCC Rcd 12540 (2020).    Section 73.406 of the rules requires licensees to notify the Commission using a Digital Notification form, FCC Schedule 335-AM, when commencing, making certain changes to, or ceasing all-digital operation.  This schedule must be electronically filed in the LMS licensing system.  Please see the filing information in the LMS Help Center.
  •   FM station digital notifications must now be filed in LMS on Schedule 335-FM.  The LMS Help Center has helpful information on the filing process.
  • Guidance Provided to FM Licensees Regarding Operations with Increased Digital Power (MM Docket No. 99-325), Public Notice, MM Docket 99-325, DA 10-866, released May 17, 2010.  [ PDF | Word ]. 
  • Digital power increase for FM stations approved.  Digital Audio Broadcasting Systems and Their Impact on the Terrestrial Radio Broadcast Service, Order, MM Docket 99-325, DA 10-208, released January 29, 2010.  [ PDF | Word ].  FM stations operating in excess of the station's authorized class may use the FM Super-Powered Maximum Digital ERP Calculator.  Other FM stations, see the Order for the calculation procedure.  News Release summary, [ PDF | Word ], released January 29, 2010.  Procedure for Filing STA Requests for Increased Digital FM Power.


What Is IBOC Digital Radio?

IBOC refers to the method of transmitting a digital radio broadcast signal centered on the same frequency as the AM or FM station's present frequency.  For FM stations, the transmission of the digital signal occurs in the sidebands above and below the center FM frequency (e.g., 97.9 MHz).  AM band transmissions also place the digital signal in sidebands above and below the existing AM carrier frequency.  By this means, the AM or FM station digital signal is transmitted in addition to the existing analog signal.  In both instances, the digital emissions fall within the spectral emission mask of the AM or FM channel (see 47 CFR Sections 73.44 and 73.317).

The present IBOC system is referred to as a "hybrid" since it is neither fully analog nor fully digital.  During hybrid operation, existing receivers still continue to receive the analog (non-digital) signal.  New receivers will incorporate both modes of reception, where the receiver will automatically switch to the analog signal if the digital signal cannot be decoded or is lost by the receiver.

Improved Quality of IBOC Digital Radio

IBOC digital radio provides near CD quality reception for stations operating in the FM broadcast band.  For AM stations, IBOC digital radio provides reception approximately equal to today's analog FM reception. Minimal impact is anticipated on reception of existing service. 

Where Can I Obtain a Digital Receiver?

The pace of development of IBOC digital receivers for consumers depends on a number of factors, including how fast and how many AM and FM stations commence digital broadcasting, and how soon receiver manufacturers can produce radio receivers.  Check with local electronics suppliers from time to time for the latest models of digital radio receivers!

 How Do I Know Whether a Station Transmits a Digital Signal?

An AM or FM licensee is required to provide written notification to the FCC within 10 days of commencing digital/analog hybrid operation.  This notice must be provided by the station's electronic filing of FCC Form 335-AM or 335-FM in the FCC's CDBS Electronic Filing System.  A "Digital Status" search field within the Station Information form in CDBS can help you identify which stations are operating in hybrid mode.  Also, an AM or FM station itself will announce if its operations include transmission of the digital signal.

For more information on AM and FM radio broadcasting, please visit the Audio Division website, and the Broadcast Radio Links page.

FCC > Media Bureau > Audio Division, (202) 418-2700.

Wednesday, January 10, 2024