**PUBLIC NOTICE**![](media/image1.png){width="0.7388888888888889in"
height="0.7458333333333333in"}

**FEDERAL COMMUNICATIONS COMMISSION** News Media Information: (202)
418-0500

**445 12th STREET, S.W.** Fax-On-Demand: (202) 418-2830

# WASHINGTON, D.C. 20554 Internet: [http://www.fcc.gov](http://www.fcc.gov/)

# ftp.fcc.gov

**DA 05-609**

**March 8, 2005**

MM Docket No. 99-325

**COMMISSION CLARIFIES POLICY REGARDING MULTIPLE AUDIO STREAMS IN IBOC
transmissions**

**Experimental authority must be requested**

On October 10, 2002, the Commission authorized the commencement of
interim operation with the iBiquity hybrid[^1] IBOC systems.[^2] Under
these interim authorization procedures, stations may use only facilities
similar to those evaluated by the National Radio Systems Committee
(NRSC). Since the NRSC's initial recommendations, certain modifications
to the IBOC system have been introduced and tested. In particular,
National Public Radio (NPR) has sponsored a program that takes advantage
of advances in audio coding technology to offer multiple digital program
channels within the bandwidth originally used for a single digital
channel.[^3] The program, known as "Tomorrow Radio^SM^," has been tested
extensively on several NPR affiliates.

NPR has filed test results indicating that the FM IBOC system can
accommodate both a main and a secondary digital program channel with
good quality and sufficient robustness for mobile service. NPR requests
that the Commission expand the digital notification procedures to permit
immediate implementation of IBOC systems with multiple digital channels.
Multicast operations do not fall within the scope of the notification
procedures authorized by the *IBOC Order.* Thus, until the Commission
modifies these procedures, licensees will be required under the rules to
obtain experimental authorizations. We also recognize that the extremely
encouraging Tomorrow Radio^SM^ test results establish the feasibility of
multiple digital audio transmissions in the hybrid mode. Accordingly, we
issue this *Public Notice* to clarify the procedures which licensees
should follow to commence multicast transmissions.

The staff will continue to authorize multiple digital audio
transmissions as experimental operations under the provisions of 47
C.F.R. § 73.1510. Requests for experimental authority pursuant to
Section 73.1510 require only an informal application, typically a
letter, and include no fee or form. The staff normally approves requests
to participate in this type of experimental program within a week of
receipt. The matter of expanded notification procedures will be
addressed in the next *Report and Order* in this proceeding. For
additional information, contact Susan Crawford or Ann Gallagher at the
Audio Division, Media Bureau at (202) 418-2700.

By: Acting Chief, Media Bureau

**-FCC-**

[^1]: The term "hybrid" refers to a system which transmits both the
    digital and analog signals within the spectral emission mask of a
    single AM or FM channel.

[^2]: *See Digital Audio Broadcasting Systems and Their Impact on the
    Terrestrial Broadcast Service,* 17 FCC Rcd 19990, 20004 (2002)
    *("IBOC Order").*

[^3]: Other participants in the Tomorrow Radio^SM^ program are Kenwood
    USA, the Corporation for Public Broadcasting, and Harris
    Corporation's Broadcast Communications Division.