FCC: Where do wireless mics fit in shrinking TV spectrum?

Wireless microphones of the type used in television productions, stage shows, lecture halls and churches operate on locally vacant TV channels. But, those channels are becoming scarce. Before the digital conversion, there were many vacant TV channels in local markets, leaving ample spectrum for wireless microphones.

The picture began to change in 2009, however, when the last full-power analog stations went off the air. Because digital TV stations can be packed more tightly than analog stations, the FCC was able to free up 18 channels for wireless use, which left fewer empty channels for wireless microphones.

A year ago, the FCC approved the first operation of “white space” devices that provide Wi-Fi-like service within some of the remaining vacant TV channels. The FCC reserved two channels in every market for wireless microphones, and provided for additional channels where needed. Nevertheless, a lot more devices will be trying to operate in a lot less spectrum. Then, last month, the FCC proposed “incentive auctions” designed to encourage broadcasters to give up still more channels.

Uses of wireless mics

Despite the squeeze on spectrum for wireless microphones, they are still indispensible in the entertainment industry. Even the FCC has acknowledged the irreplaceable nature of these devices. For decades, the agency issued licenses for TV-band wireless microphones to just a few categories of users: broadcasters and broadcast networks, cable TV operators, and movie and TV producers.

Other users, such as concert venues, college lecture halls, churches and even the FCC (in the context of its own meeting room) operated wireless microphones without authorization. But, these illegal operations, well known to the FCC, were well managed and caused virtually no interference to TV stations.

Interim rule-making

The advent of white-space devices, though, brought the need for better control over who uses microphones and where. Bringing regulation into line with reality, in 2010, the FCC considered broadening the list of eligible licensees. It also took the unusual step of proposing to legalize previously illegal operation by allowing lower-power wireless microphones to operate as unlicensed devices, under the same basic rules as Wi-Fi and cordless telephones. The power limit would be lower than for licensed wireless microphones, but higher than for most other unlicensed devices, and should suffice for good sound in most halls and churches. That proposed relaxation has not yet been adopted.

Use of digital microphones

In an inquiry proceeding launched in October, the FCC wants to know if technological advances will solve the spectrum problem. The theory is if digital TV stations can fit four channels into one analog TV channel, and digital cell phones can carry 20X the traffic in the same spectrum as old analog cell phones, then why shouldn’t digital wireless microphones allow similar service improvements?

In fact, digital microphones each take up about as much spectrum as their analog counterparts, but digital devices can be squeezed much closer together. Therefore, a TV channel can accommodate at least a dozen of them as compared to half as many analog microphones. However, compression of the digital signal creates audio delays that can lower the quality of digital transmissions. The Commission’s notice of inquiry is looking for a way forward by seeking comment on these and related technical issues.


  • On Feb. 1, 2013, TV and Class A TV stations in Indiana, Kentucky and Tennessee must begin their pre-filing renewal announcements in anticipation of filing their renewal applications on April 1, 2013.
  • On or before Feb. 1, 2013, non-commercial TV stations in Arkansas, Louisiana and Mississippi must file their biennial ownership reports.
  • On or before Feb. 1, 2013, television stations, Class A TV, LPTV stations and TV translators in Arkansas, Louisiana and Mississippi must file their license renewal applications.
  • On Feb. 1, 2013, TV and Class A TV stations in the following locations must post their 2012 EEO reports on the FCC’s new public file web page and on their own websites: Arkansas, Kansas, Louisiana, Mississippi, Nebraska, Oklahoma, New Jersey and New York. 

Harry Martin is a member of Fletcher, Heald and Hildreth, PLC.