Most Popular Articles
The value of the subcarrier
The FCC originally enacted the Subsidiary Communications Authority (SCA) in 1955. In 1983, the FCC eliminated the licensing requirement for SCAs that subsequently permitted radio stations to use their subcarriers to broadcast essentially anything. Prior to that, they were primarily voice-type services that included reading services, foreign language broadcasts and, lest we forget, the static and hiss laden sounds of the background music services (elevator music). After this ruling, stations could host a variety of new emerging services using not only analog voice information, but also data transmissions. Companies such as Cue Paging and Bonneville Data began to frantically negotiate leasing arrangements with stations in the top 50 markets. In a short time, these companies were broadcasting a variety of subscription-tailored data to end-users. The data included custom news, sports, weather, stock/commodity info and messaging/paging. The value of a subcarrier lease began to climb, particularly to those stations with the largest coverage footprint within their market. Of course, several stations in each market were locked into long-term contracts with the background music services for a fraction of the money offered by the data services.
The Microsoft SPOT watch displays subcarrier data from two stations in a market.
In 1993, the Radio Broadcast Data System (RBDS) standard was introduced as a means of using the subcarrier to broadcast specific information that permits a receiver to tune stations based on format and provide traffic, program and emergency broadcast information. The receiver manufacturers supported the effort and began to rollout receivers shortly thereafter. While several stations continue to broadcast RBDS, it doesn't appear to be used to the level for which it was originally intended. Because the individual stations initiate RBDS, it provides no monetary value.
In 2003, most, if not all, of those services are no longer in existence. They have been replaced by emerging terrestrial services, such as PCS/cellular, that can provide all of a users information needs within a single pager-type receiver and with a virtually contiguous national footprint. Background music services have moved to satellite-based delivery, where it can also offer a much wider range of content, as well as other data services. Analog reading services still widely use FM subcarriers; however, from a value standpoint, it does not present a significant monetary impact, as these are typically provided by a station free or at minimal cost.
Alternative data delivery
Wireless data delivery is without doubt the hottest field in telecommunications and the computer industry. The FCC has recognized this and has been continuously working to develop new spectrum that can support this fast growing industry. Let's face it, subcarriers have problems — one-way only transmission, multipath issues, limited bandwidth, signal-to-noise issues, reduced RF footprint (related to the main carrier), poor performance penetrating buildings and a lack of subcarrier-specific receivers. As a practical matter, the SCA is a narrow alternative for the transmission of data.
Value is driven by demand. In the case of a subcarrier, we need to look at alternative delivery methods. As a society, we have grown accustomed to having all of our information readily available in one place. The wireless carriers have generally done a good job responding to this need by integrating voice, messaging and data into a single phone or PDA device.
Additionally, the advent of unlicensed spectrum that can be used for wireless Ethernet transmissions are opening up yet another alternative means to gather information remotely. WiFi hot-spots are continuously becoming available in venues where people eat, relax or otherwise have time to use their laptop computer or any Web-enabled device to send and receive e-mail.
A new kind of SPOT
If you want to know who is investing money into FM subcarriers, look no further than the computer giant Microsoft. It seems that Bill Gates has a vision to provide a full suite of information to a user's watch using FM subcarriers. Microsoft will create a nationwide subcarrier network called Direct Band that is expected to cover the top 100 metropolitan areas in all 50 states and 13 Canadian cities. The network will use subcarriers from two stations in each city and with an expected throughput of 12kb/s. The software behind this concept is called SPOT, or Smart Personal Objects Technology, which can deliver not only the usual news, sports, weather, traffic and time, but also will permit the user to customize the watch face—definitely something everybody has wanted.
Providing data in addition to the audio is a subcarrier function that is being carried over to DAB.
Traditional data delivery
As an alternative to satellite-delivered data services, Mainstream Wireless markets real-time data delivery via FM subcarrier. The ability to broadcast data to locations that cannot install external receive antennas due to local zoning restrictions is its major advantage. While it sounds like a viable application, the size and form-factor of satellite antennas are becoming almost invisible and it is likely not to trigger jurisdictional reviews, so why not just use the satellite receiver?
A company called C3 Technologies is developing a technology using the FM subcarrier. One such application is called Claricast Digital Wireless Voicemail System. This is a technology that sends subscribers voicemail using FM subcarriers. Here is an interesting application that could prove to be an opportunity for broadcasters. The company is also working on data broadcast applications in the military, homeland defense and public service sectors.
Stratosaudio is another company that is embracing RBDS technology by providing services to create station branding, listener interaction and channel commerce opportunities. The RBDS-ready receiver is the consumer's front end, while a cell phone or Web browser is the back end.
IBOC and the subcarrier
The advent of digital radio will bring a mixed bag of opportunities and losses for broadcasters. Broadcasters currently leasing the 92kHz subcarrier will likely lose that revenue stream or face the need to replace existing receivers.
Companies such as Impulse Radio will permit broadcasters to leverage the data stream into new forms of business — selling and managing multiple data streams. The applications Impulse Radio uses as examples include: program-associated data, on-demand programming, time-shifting, telemantics, commerce, listener interaction, subscription, supplemental audio, messaging, electronic program guide and Emergency Alert System. Think RBDS on steroids and without the subcarrier.
McNamara is president of Applied Wireless, Elkins Park, PA.
Acceptable Use Policy blog comments powered by Disqus
[an error occurred while processing this directive]
Today in Radio History
The history of radio broadcasting extends beyond the work of a few famous inventors.
EAS Information More on EAS
The feed provides feeds for all US states and territories.
Need a calendar for your computer desktop? Use one of ours.
Information from manufacturers and associations about industry news, products, technology and business announcements.
When Northern Community Radio set out to build a new community radio station in rural northern Minnesota 38 years ago, naysayers said that it would be broadcasting “only to a bunch of gophers
Browse Back Issues[an error occurred while processing this directive]
Also in the July Issue
- Trends in Technology: Robust IP STL
- LPFM on The March
- RF Engineering: Modern Modulation Techniques
- Field Report: Tascam TH-2000 Headphones
- Battery Maintenance: Testing and Charging