` Wireless Microphones and the FCC Incentive Auction: Key Facts For Broadcasters Leading into 2017

Wireless Microphones and the FCC Incentive Auction: Key Facts For Broadcasters Leading into 2017

Almost every venue, studio and mobile broadcast crew that uses wireless microphones will need to reconfigure their systems by 2020 to comply with new federal regulations. Since the definition of wireless microphones includes in-ear monitors, intercom systems, and interruptible fold back (IFB) systems, more devices will be impacted than most people realize.

Pending the outcome of the auction, wireless microphone operators should expect that:

  • A large portion of the upper UHF spectrum, specifically in the 600 MHz band will be repurposed and become unavailable to mics around 2020…sooner in some areas.
  • About half the existing UHF equipment is likely to be rendered obsolete, or require modification (if allowed: FCC decision is pending).
  • Customers should plan to start replacing equipment in 2017 and complete their transition by 2020.
  • There will be pockets (guard band and duplex gap) in the repurposed spectrum where mics will be allowed to operate but under different rules (detailed below).
  • The two microphone reserved channels that currently exist in each geographic market are being eliminated. However, mics will have portions in the guard band and duplex gap for exclusive operation. Also, there will be at least one white space channel in every market area. It will be shared between mics and white space devices (WSD). WSD are a relatively new class of unlicensed equipment that also operate on locally vacant TV channels. A licensed mic operator can reserve any locally vacant TV channel for their event, preventing WSD from operating on the channel(s) during the production.
  • The FCC will require manufacturers, integrators and retailers that sell wireless microphone systems to post notices at point-of-sale, on websites, packaging, and literature about vacating 600 MHz and the new operating rules.

Incentive Auction Process Explained
The FCC incentive auction has a multi-stage structure designed to let market forces match spectrum supply with demand. If a stage fails to meet certain criteria, a new stage is initiated re-purposing less spectrum (the top of the following FCC chart indicates the last possible stage of the auction).  When the federal government published the FCC incentive auction Report & Order (R&O) it included the possibility that repurposed spectrum (blue and grey blocks) could extend down to 548 MHz (the bottom, scenario 12 on this chart):


This was changed to 566 MHz (scenario 10, a.k.a. the initial clearing target or Stage 1) shortly before the auction opened on March 29, 2016. On December 13th, the auction entered Stage 4 (scenario 7) taking an additional 24 MHz (four TV channels) off the auction block, a significant reduction compared to previous stages. Now that band plan scenarios 8 through 12 are off the table, we know the repurposed spectrum will not go below 614 MHz. So, at minimum UHF TV channels 14 – 36 will remain available for microphone operation under traditional regulations.

Stage 4 Clearing Target Band Plan

(one possible outcome of the auction, as of 12/16/2016)

Lower channels 14-20 that are not pictured, also remain available to mics:

 UHF channel 37 has not been used for TV broadcast. Rather, it is used for wireless medical telemetry (WMT), for example to monitor a patience’s vital statistics in a hospital. It is also used in a few remote geographic areas for radio astronomy (RA) studies. Wireless mics have never been permitted to operate on channel 37. This is not changing.

This leaves the majority of the UHF TV band unchanged. This is important for wireless microphone operators because these frequencies have very favorable characteristics. They travel through walls, achieve extended range from low transmitter power, use compact antennas, etc. A prime message that many in our industry conveyed to the FCC has been that UHF must remain part of the spectrum portfolio available to wireless microphones, especially for hypercritical applications. Regardless of the auction outcome, the audio industry has successfully gained access to alternative prime spectrum outside the UHF band, especially useful for licensed microphone operators.

Co-channel Operation
The Commission revised their rules for operation of microphones on the same channel used by a UHF TV station (co-channel operation). Previously, mics were only permitted to operate on a TV channel with a minimum separation distance of 100 km (~70 miles) between the mic and the TV broadcast antenna. Now, mics can operate 4 km outside the actual service contour of a TV station, regardless of the location of the TV antenna. Licensed microphone users are permitted to operate closer or even within the service contour, if they are indoors and the TV signal measures less than -84 dBm. This field strength benchmark, rather than the traditional geographic separation from TV transmit antenna, opened a number of UHF channels that would otherwise not be allowed.

Operating in the Guard Band & Duplex Gap
An 11 MHz buffer range known as the duplex gap will exist between the forthcoming 600 MHz uplink and downlink mobile broadband blocks. There will be no devices allowed to operate in the lowest megahertz, adjacent to the downlink block. The next 4 MHz will be for licensed mic operators exclusively (not shared with white space devices). This will be particularly useful for electronic news gathering (ENG) crews covering spontaneous events. The upper 6 MHz of the duplex gap will be shared by unlicensed mics and white space devices.

A lower guard band separating mobile broadband from TV broadcast or channel 37 will exist; the size will depend on which stage the auction closes. There will be no devices allowed to operate in the upper megahertz, adjacent to the downlink block. In the example scenario 7 (if auction closes in Stage 4), wireless mics would have exclusive use of the remaining 2 MHz (614-616 MHz). If the auction continues beyond stage 4, a majority portion of each guard band will be shared between unlicensed mics and WSD, but 2 or 4 MHz will be exclusive to mics, depending on which band plan scenario plays out:

Microphone transmitters will be limited to 20 mW effective isotropic radiated power (EIRP) output when operating in the guard band or duplex gap. It is noteworthy that this specification has traditionally been measured as conducted power at the transmitter’s antenna terminal. EIRP, a measurement based on use of a theoretical isotropic omnidirectional antenna, will yield slightly different results. A factor to also consider is that the guard band and duplex gap are buffers that avoid interference between adjacent services and thus may have out-of-band emissions (basically noise) from those services. Therefore, the possibility of interference to mics operating in these pockets may be high, especially considering the low 20 mW mic power limit.

Unlicensed mics operating in the guard bands and the duplex gap will need to register with a database administrator and may be assessed a fee, although the procedure is not specified yet. Other than the 4 MHz within the duplex gap that is reserved for licensed users, mic operation in the other portion of the duplex gap and the lower guard band will be considered unlicensed. This means licensed operators will have no priority or rights to reserve these pockets, unlike TV white space channels.

Licensed Vs. Unlicensed Mic Operation
The FCC is making a clearer distinction between licensed and unlicensed mic operation. Parties that are eligible, such as broadcasters, motion picture producers, cable stations, and creators of broadcast content, should apply to obtain licensed status to take advantage of the rights and privileges afforded to them. These include registration for interference protection from white space devices (WSD) in the TV database system as well as access to additional licensed bands outside of UHF.

Other highlights:

  • The current 944-952 MHz studio transmission link (STL) band has effectively been expanded to include portions within 941-960 MHz and will be open to all licensed mic operators (not just broadcasters). 941-944MHz (3MHz) and 952-960MHz (8 MHz) would be shared with Multiple Access Systems (MAS) and Fixed Microwave. Some specific frequencies will not be permitted for mics. Operation in the STL band should still be coordinated with the local Society of Broadcasters (SBE) frequency coordinator.
  • 169-172 MHz (just below high band VHF TV channels) rules were revised to make it more practical for professional mics.
  • 1435 – 1525 MHz (generically known as the 1.4 GHz band) will be available to licensed mics but will require equipment with an electronic key (yet to be introduced in the market) and an approval process for each production. This range is intended for “power users” requiring around 100 microphone channels or more, at fixed locations (as opposed to mobile news teams). Operation in this range will be secondary to aeronautical mobile telemetry (AMT), a.k.a. flight training. This range is coordinated by The Aerospace and Flight Test Radio Coordinating Council (AFTRCC). The equipment will incorporate location, date and time awareness. AFTRCC will provide a digital code (the electronic key) that will unlock the equipment, enabling it work to at the approved time and location. Several details still need to be worked out between the audio industry and AFTRCC, including creation of a portal by our industry to funnel applications to AFTRCC.
  • 6875-6900 and 7100-7125 MHz are available to licensed mic operators. These two 25 MHz blocks are the “bookends” of a range that is assigned to wireless video. Therefore, their use by audio engineers should be coordinated with their video counterparts. The short wavelengths of these high frequencies will largely limit the usefulness to short range, line-of-sight applications, such as a reporter using a handheld mic standing directly in front of a video camera.
  • White space database administrators will “push” information about changes in channel availability to white space devices (WSD) operating in the area where licensed wireless microphones require protection, so that these channels can be reserved in about twenty minutes. This is a significant reduction in time compared to 24 hour WSD polling method that has been in use. This greatly benefits news teams covering major stories. The number of WSD in use is currently limited but could increase significantly in the future. Therefore, registering for protection will become more critical.

Equipment That Can Be Purchased With Confidence
Many wireless microphone systems have been introduced in unlicensed ranges, such as 902 – 928 MHz, 1.9 GHz (DECT) or 2.4 GHz, in part due to the uncertainty the auction posed on the UHF band. Mic systems work fine in these unlicensed bands if the RF environment where they are operating is tame. However, unlicensed bands are open to a plethora of devices (cordless telephones, wireless routers, drones, robots, etc.), so interference can occur among those operating in close proximity to each other.  For those that do their homework, the UHF band is more predictable because use is limited to specific devices and services. Therefore, UHF is still preferred for professional and semi-professional applications. It is important to keep in mind that any wireless mic that will have the ability to tune to any frequency within the repurposed spectrum will need to be taken out of service in about three years after the auction closes and the FCC is yet to rule on a petition to allow modification of such equipment. Although the outcome of the auction and some regulatory details are still pending, you can confidently acquire any UHF system that does not have the ability to tune above TV channel 36 (608 MHz).  This upper limit may increase if the auction progresses into further stages. In the future, if you need to configure systems with a large number of wireless microphones that require more spectrum than the UHF TV band can accommodate, than it is important to determine if your customer qualifies to be a licensed operator. Licensed operators would be best served by first adding additional mics in the 941-960 MHz band, and then applying for use of 1.4 GHz for mega-installations. Unlicensed operators can add additional mics in the guard band, duplex gap and the various unlicensed bands that are available.

Of course, our industry would prefer that the entire 600 MHz band remain available to mics. However, the continued availability of lower UHF, together with the access we recently gained in several alternate frequency ranges, ensures that the future includes plenty of wireless microphone systems and the trend for increasingly sophisticated productions will continue.

Ever since the dawn of radio, policies regarding the use of spectrum have continually changed. That won’t end with the conclusion of this incentive auction. It is important to recognize that the incentive auction centers around how content is distributed. Adequate spectrum is also essential for content creation. The United States is the undisputed global leader in news and entertainment content. U.S. core copyright material is a $1 Trillion industry (that’s Trillion with a “T”) and has a 3-to-1 export-to-import ratio, the highest of any American made product or service. Therefore, it is vital for the audio industry to continue to work cooperatively with the FCC so that the Commission fully understands the importance and ubiquitous nature of wireless mic operation in U.S. society. This is especially true since FCC leadership will change with the new presidential administration.


Joe Ciaudelli is Director of U.S. Spectrum Affairs for Sennheiser Innovation & Research. He is a private sector advisor in the U.S. delegation to the International Telecommunications Union (ITU), the United Nations specialized agency on information and communications. He is also the founder of Rayvel, a corporation that specializes in electro-magnetic science, and holds three patents in holographic technology.

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