Published in October 2008

700MHz Allocation Stirs Industry Concerns
By By R. David Read

FCC actions leave wireless mics in limbo.

Performers may be using differently configured wireless equipment after everything is sorted out. Here, Ben Vereen is on stage at the Birch North Park Theater in San Diego.

The future use of wireless microphones has again raised its ugly hackles. With the impending transition of television transmission from analog to digital by February 2009, the frequency spectrum previously allocated by the Federal Communications Commission (FCC) to certain analog UHF-TV channels will cease to exist. Most of this spectrum has already been auctioned off for sizable sums to bidders who seek to expand their interests in the 700MHz wireless spectrum.

Recent proceedings and proposed rule changes will effectively bar use of (licensed or unlicensed) wireless microphone and other low-powered auxiliary devices in the entire 700MHz band (698MHz to 806MHz, UHF-TV channels 52 to 69) after the February 2009 transition.

Key Words

Here are the key words in the Notice of Proposed Rulemaking document from the FCC, dated August 15, 2008 (released August 21):

In the Order below, we impose a freeze, effective upon release of this Order, on the filing of new license applications that seek to operate on any 700MHz Band frequencies (698-806MHz) after the end of the DTV transition, February 17, 2009. In addition, we impose a freeze on granting any request for equipment authorization of low-power auxiliary station devices that would operate in any of the 700MHz Band frequencies. We also hold in abeyance, until the conclusion of this proceeding, any pending license applications and equipment authorization requests that involve operation of low-power auxiliary devices on frequencies in the 700MHz Band after the end of the DTV transition.

By FCC definition, “low-power auxiliary station devices” include licensed and unlicensed wireless microphone systems and TV camera synchronized control mechanisms. The complete text of the FCC docket can be accessed at lic/attachmatch/FCC-08-188A1.doc.

click to enlarge*

The above graphic shows how the UHF spectrum will appear after the transition date and who the primary bidders were for the auctioned-off portions of the spectrum. Successful bidders for the available space generally are referred to by the FCC as “Commercial Wireless Services.” It should be noted that the bulk of the auctioned spectrum was gobbled up by telecommunication companies with an eye to expanding cellular and similar applications. In this high-stakes game, it’ll be difficult for the relatively low profile, small-cap or unlisted (private ownership) wireless microphone manufacturers to compete.

Initially, the portion of the spectrum under discussion was reserved for FCC licensed (italics added) users in the broadcast field. By industry best estimates, there currently are 943 licensed wireless microphone users and possibly 3.5 million unlicensed users in this band. Utilization of UHF-TV stations on the previously available channels 52 through 69 was scant, which paved the way for the production and usage of wireless microphone systems.

In no way was the requirement for licensing rescinded; however, most users either did not qualify or simply chose not to file for licensing of their equipment. And, it must be emphasized that the licensing requirement was placed on the user, not the manufacturer and/or the dealer. If that sounds like a copout, it was fostered by the FCC that, by virtue of either an unwillingness or inability to enforce the law, taciturnly allowed the process to proceed unimpeded for better than three decades.

In almost every case (and certainly on the part of the major suppliers of wireless microphone systems), such equipment was duly tested for type acceptance in order to follow FCC regulations and was stringently manufactured with regard to power output and spurious radiation. Which isn’t to say that there wasn’t some real “junk” dumped on the market, but most reputable suppliers proceeded in a due and diligent manner.

Responding To The Change

The cited FCC order stops somewhat short of completely banning the production, importation or use of wireless microphone (and other) lower-power auxiliary devices (refer to FCC Docket 08-188A1). However, the writing is on the wall. (Note: The proposed FCC rules apply only to devices for use within the United States. Devices for use on the 700MHz band in countries other than the US are not currently affected.)

Wireless microphone manufacturers, such as Audio-Technica, Lectrosonics, Shure, Sennheiser and others, have been advising their dealers for more than a year that manufacturing of 700MHz devices would be discontinued, and some have required dealers and/or users to sign waivers absolving the manufacturer from liability for devices that likely will be illegal for future use.

With the likely advent of a total ban of wireless microphone systems in the US 700MHz band, what are the alternatives? Some relief for current 700MHz band customers may lie in the modification of existing equipment into alternative bands. For example: Lectrosonics recently issued the following information to its dealer base:

Lectrosonics has implemented a service plan that allows end users who have current equipment in this band to do block changes. For some products, such as IFBR1a and VRS/VRT Modules, an exchange is the lower cost pathway. While not inexpensive, this plan provides a more cost effective pathway for those who choose to change the blocks of their equipment. These block changes involve entire RF board changes.

Have your customers contact Lectrosonics directly for return authorizations and instructions regarding these block changes.

Older products, such as 200 series, 195 series, etc., will not be covered under this program. Frequency changes may be possible. Call our service department to inquire about feasibility.

In November of 2007, we notified all dealers that we would no longer build blocks 27, 28 or 29 to inventory and that all orders for those blocks would be on a special order, no return basis.

Shure Inc. has issued similar notification to its dealer base and, if they have not already, other manufacturers undoubtedly will be quick to follow suit. All of the manufacturers contacted for purposes of this report offered some form of plan that seeks to ameliorate the effects occasioned by this transition. It would be prudent to contact your wireless microphone supplier(s) to determine what recourse might be available.

Grey Area

An even larger battle is looming on the horizon. Inasmuch as it appears to be a foregone conclusion that wireless microphone manufacturers will shortly have to shun the 700MHz band, they will have to seek out alternative spectrum space to continue meeting customer demand. Given current technology and the immutable laws of physics, this presents a situation requiring some serious equipment alteration or the adoption of some, yet unforeseen, mode(s) of operation. Fortunately, the spectrum from 470MHz to 698MHz remains available to licensed users, as it has been for some time.

The next battle royal shaping up is over use of so-called “white spaces” between active TV broadcast channels. These are niche spaces (outside of the 700MHz band) in the UHF range, and are on different frequencies in each metro area. The insatiable appetite for band-space by WiFi, PDA and other wireless providers is being fostered by some rather well heeled suppliers to the point where the right of wireless microphone users to share these frequencies is under intense attack.

At present, the FCC does not legally recognize “white space.” Inasmuch as the transition to DTV will render a greater amount of available bandwidth (white spaces), it is not inconceivable that such space might be identified and subsequently offered at auction to the highest bidder. Currently, several major companies, including Google and Microsoft, are vying to have unlicensed access to these spaces.

By using known “search and avoid” frequency scanning, interference between co-users could seemingly be avoided (such procedures are already in common use by wireless microphone manufacturers). However, the bandwidth grab by contesting commercial wireless providers appears to have rendered any serious efforts to adopt such technology as moot; in field tests thus far, their “seek and avoid” efforts have failed miserably. Hence, they have chosen to take their battle to the political arena.


In the long run, it is hardly conceivable that wireless microphones will disappear from the AV scene. However, an arduous battle for equality appears to be in the offing. On the bright side, this state of affairs may well spur some intense R&D efforts on the part of wireless microphone manufacturers that will circumvent mutual interference between co-users, and usher in new digital and modulation schemes that will further advance the technology as it applies to this sector.

Stay tuned….

Contributing Editor R. David Read has been involved in AV and RF development for about 40 years.

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