Wireless mic users must prepare to dance a spectrum hokey-pokey to adjust to spectrum reductions, new operating rules

The Pope will visit the U.S. in late September, which is already prompting extensive preparations in many quarters. Among those readying themselves: news operations, professional wireless microphone operators and wireless mic frequency planners in several major cities where Francis is scheduled to drop by. They’ve got to figure out how many wireless mics will be needed to stage, cover and record the various events … and then they’ve got to figure out how to coordinate the spectrum necessary to make sure all those mics serve their various purposes.

Newscasters will want to be sure that they can deliver clear on-site audio feeds to audiences over whatever medium – broadcast, cable, satellite, the Internet – the audience may choose. Those who venture out to see the Pope in person will want to clearly hear his every word. And still others – historians, archivists, those who want a permanent record of some (or all) of his visit – will want to insure the availability of high-quality recordings. For the most part we have come to assume that all of these needs will be met. What we often lose sight of is the fact that event coordinators must struggle to stretch the limited spectrum available for wireless mics to accommodate the various uses.

And with two recent orders (you can find them here and here), the FCC has just make their jobs even harder in that regard.

As long-time readers know, traditionally wireless microphones operated in the TV spectrum until 2009. But since then, a series of Commission decisions (including some made at Congress’s direction in connection with the upcoming incentive auction) have reduced the spectrum options for mics. And the reductions continue: With plans to auction off 100 MHz or more of the current TV spectrum to wireless carriers – while scrunching TV stations displaced by that into the ever-shrinking portion of the spectrum reserved for TV – the FCC has decided to reduce microphone access to UHF channels even more. On the upside, though, the Commission has concurrently opened some other bands for wireless mic use.

As a result, wireless microphone users now must prepare to dance a spectrum hokey-pokey, with some new rules to follow (and new spectrum to access as soon as those new rules are adopted); other rules that will apply during transition periods; and still more rules that will take effect with the transition of new 600 MHz spectrum licensees to UHF. And when it comes to spectrum options, they won’t know exactly how much spectrum will be available to them, or where it will be located, until the incentive auction is over.

Let’s start with the good news. 

Licensed mics will be able to operate closer to co-channel TV stations by relying on a “sensing threshold” of -84 dBm (when indoors and under other conditions). Previous rules permitting co-channel operation when the TV station is at least 4 kilometers away (or after coordinating with TV licensees) will remain in effect as well.

Two UHF channels will be available for shared use by wireless mics and white space devices. The channels will consist of: (1) a “preserved white space” channel where mics will share with white space devices; and (2) the Duplex Gap between wireless uplink and downlink channels. The Gap will be divided into one 4 MHz block reserved exclusively for licensed mics and a 6 MHz block where unlicensed mics will share with white space devices. Recognizing that in some TV markets the Duplex Gap may have to be made available to a TV station, the Commission is proposing to provide a second “preserved white space” channel in those markets. This proposal will be addressed in a pending rulemaking.

Depending on various auction outcome scenarios, unlicensed mics will share with white space devices most of the guard band between television and wireless downlink spectrum and will get to use 2 MHz of the 3 MHz of spectrum in the guard bands closest to TV Channel 37.

Licensed mic users may also “reserve” spectrum otherwise shared with white space devices. This can be done on short notice and/or for specific needs, e.g., breaking news coverage or particular events (e.g., concerts, gatherings, etc.) that involve extensive mic use. But there will be a slight lag time: the licensed mic user must notify a white space database administrator and request channels for immediate use; the administrator will then have 10 minutes to notify other administrators, and all administrators will then have 20 minutes to “push” notice out to any white space devices operating in the area, advising them to clear the channels.

New spectrum will be available for licensed wireless microphone operators in 941.5-944 MHz, 952.85-956.25 MHz, and 956.45-959.85 MHz. Use of any of those bands will be subject to coordination with the local SBE coordinator. And 944-952 MHZ, previously available only to certain licensed users, will now be open to ALL licensed mics, also subject to coordination.

Also, in certain limited circumstances, wireless mics will now be able to use 1435-1525 MHz – a band currently used for communications relating to flight tests – subject to coordination with the Aerospace and Flight Test Radio Coordinating Council (that’s the test flight spectrum coordinator). Pre-operation authentication and verification confirmation will also be required to use 1435-1525 MHz, through specific procedures and requirements must be worked out. Use of this particular option will be limited to specific fixed locations, such as large venues (outdoor or indoor), where large numbers of mics (typically 100+) are needed for specified time periods, i.e. situations in which other available spectrum resources are insufficient.

And other, better bandwidth channels will be available on 169-172 MHz for Part 90 licensees, while two 25 MHz channels at the top and bottom of 6875-7125 MHz will be opened for Part 74 (and Part 78 CARS) licensees. Use of both bands will be subject to coordination.

Now the bad news.

The FCC rejected requests to “grandfather” existing equipment. As a result, a large amount of UHF microphone equipment currently owned must be tossed by 39 months after the Commission issues its “Channel Reassignment PN” placing TV stations in their new channels, an event we estimate is not likely to happen until June 2016 at the earliest. (Note two very marginal exceptions: some equipment may be modifiable, though this will be costly, and some mics may still fit within the new technical requirements.)

The FCC also rejected requests to assist a subset of professional wireless mic users protect their operations. Some such users are “unlicensed” because they use fewer than 50 microphones – think regional theaters like the Signature and Steppenwolf and orchestras even as large as the Houston and Baltimore Symphonies. Proponents had suggested a mechanism for such groups to register for protection from white space devices. The Commission declined to provide such a mechanism.

Unlicensed mics choosing to operate in the 600 MHz may operate in the Duplex Gap and guard bands, but do so, but only with 20 mW EIRP, and they must register with (and pay any required fees to) white space database administrators. They also may no longer register for protection from white space devices.

Licensed mics may only operate in 600 MHz at 20 mW EIRP in the Duplex Gap. That’s bad news because, generally, licensed mics are allowed more than 10 times that (i.e., 250 mW power).

Where does this leave the industry? 

Users must plan well-ahead to determine whether and when new equipment must be purchased, what spectrum may be available to them, and when specific operating rules go into effect. Once the incentive auction is done and the FCC makes new TV channel assignments, a 39-month transition period will begin where mics can operate in the 600 MHz Service Band, but after the transition they must vacate all of the 600 MHz Service Band except for the Duplex Gap & guard bands (licensed mics must vacate all of the 600 MHz Service Band except for 4 MHz in the Duplex Gap). Professional users that do not qualify for FCC licenses will not have access to any of the new spectrum and will need to determine how to continue to provide professional events while sharing spectrum with white space devices (from which they will no longer be able to register for protection).