This myth can be attributed to confusion over the legal status of certain technologies that can be used in connection with an analog radio signal. This myth was further promulgated by an incorrect article in a trade magazine.
There are various technologies that have been authorized by the FCC over the decades that can be used to enhance the viability of an analog FM radio signal.
Subsidiary Communications Authority (SCA) uses a portion of the FM station’s allocated bandwidth outside of what is used for monophonic and stereophonic audio services in order to transmit one or more audio programs. These are commonly referred to as “subcarriers”. SCA was commonly used by radio stations, on a leased-access basis to broadcast “closed circuit” audio services such as background (elevator) music (Muzak) and other audio services to subscribers of the lessor using radio receivers specifically designed to receive the audio service. It is also commonly used for radio reading services for those with visual impairments, again using dedicated radio receivers issued to the listener by the organization operating the reading service. SCA receivers are not available the the general public. In fact, decades-old laws exist in the US Criminal Code that places penalties on unauthorized distribution of radio receivers that can intercept SCA communications.
In Band On-Channel (IBOC) Digital Audio Broadcasting (DAB) is a proprietary technology of Xperi. IBOC DAB uses the FM station’s authorized bandwidth to provide audio and data programming services on spectrum that is not used for monophonic and stereophonic analog transmission. This product is marketed as “HD Radio”. A feature in IBOC DAB is the ability for a single radio station to carry, in addition to their analog signal, one or more additional programming “streams” using digital transmission. To listen to these programming streams, a radio receiver capable of decoding IBOC DAB/HD Radio is required. HD equipped receivers are available to the general public.
§73.593 (which also applies to LPFM stations by reference in §73.801) allows noncommercial stations to use their SCA capacity for remunerative (getting paid for it) use as long as such use is not in the detriment of of operating radio reading services for the blind or otherwise inconsistent with its public broadcast activities. Based on this, a LPFM station can provide commercial services through an SCA, but it is not considered a “broadcast service” as the availability of radios are limited to specific purposes under federal law.
Subpart C of Part 73 contains all of the rules related to IBOC DAB. When the FCC was establishing the digital television (DTV) service, it concluded at that time that since multicast streams could be received by a DTV receiver, those streams were considered “broadcast services” and therefore subject to the rules that also applied to their primary signal. After the FCC created IBOC DAB in MM Docket 99-325, they concluded that additional audio services provided through HD streams (multicast) were similar to the additional streams provided by DTV stations and as such, they were considered as broadcast services, subject to the rules that apply to their main audio channel, this includes §73.503(d) which states the noncommercial nature of LPFM and full-service NCE broadcast stations.
FACT: LPFM stations cannot use their HD-2, HD-3 or HD-4 streams for commercial operations and must comply with the noncommercial nature of NCE policy.
