Microphone Mythbusters Vol. 1 – UHF Spectrum

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by Gino Sigismondi

In Microphone Mythbusters Vol. 1, Gino Sigismondi from Shure addresses questions on the UHF Spectrum.

Welcome to the first edition of Microphone Mythbusters! My name is Gino Sigismondi, Technical Training Manager at Shure Incorporated, and I will be your guide as we attempt to separate fact from fiction regarding the crucial input stage of the sound system. I have been part of Shure Applications Engineering for the better part of 12 years, and a “sound guy” for longer than that. It would be a complete fabrication to say I didn’t believe many of the myths we’ll be discussing when I first came to work at Shure, because I learned the sound trade the way I’m sure many of us did – on the job. This is how legends get passed down. But I’ve had the extreme good fortune to work with a number of really smart people here at Shure, and soon learned that many of the “facts” that I held as truth turned out to have little scientific basis. And judging by many of the common questions we get on a daily basis, many of these myths still perpetuate.

As I wrestled with which misconception to tackle first, I figured the best place to start might be with something timely – spectrum issues for wireless microphones. Given that the June 12th deadline for ending wireless microphone operation above 698 MHz has just recently passed, it seems like a good time to take stock of all the issues on the table and how you might be affected. Since the dawn of the DTV transition in the late-90’s, fear and misinformation have been the name of the game in the UHF spectrum. (Anyone remember “DTV Cometh?” Well, DTV cometh, analog TV went-eth, and lo and behold, UHF wireless microphones still work-eth!) Let’s break it down:

Myth #1: I’ve heard the FCC is taking away spectrum from wireless microphones. Is this true?

This is actually a more complicated question than it seems, because the answer is actually yes and no. Most people who ask this question mentally insert the word “all.” As in, “The FCC is taking away all spectrum from wireless microphones.” This is simply not true. However, the 700 MHz auctions and Public Safety reallocation has resulted in 108 MHz of the UHF television band being repurposed for other services. With AT&T, Verizon, Qualcomm, and other regional providers who purchased the rights to use different blocks of the 700 MHz spectrum,  gearing up to roll out their new services soon, this past January the FCC finally issued a report and order officially “booting” wireless microphones out of 698 to 806 MHz (TV channels 52 – 69). This includes the sale, marketing, distribution AND operation of 700 MHz wireless microphones (or in-ear systems, or comm systems…you get the idea). This means that if you or someone who know has a wireless audio device that operates on these frequencies, they need to stop using it. And don’t even think about trying to sell it on eBay. That is illegal, too.

Many people wonder, rightfully so, how the FCC plans to enforce these rules. Enforcement at the FCC has largely been complaint driven, which means someone would need to figure out you’re operating on frequencies you shouldn’t be, and file a complaint with the FCC. In this case, the complainer could be an entity as large as Verizon. Choosing to ignore these rules simply because, “It’s extremely unlikely that I’ll get caught” is akin to speeding down an open highway late at night because, “There probably won’t be any cops way out here this late.” That may be true, but if you get caught, you will still be punished. From an FCC press release issued on May 28th: “Because any operation in violation of these rules creates a danger of interference to important radio communications, users who operate wireless devices in violation of these rules may be subject to monetary forfeitures, seizure of the radio equipment, or criminal sanctions.”

Obviously, there’s a substantial amount of equipment out there that operates in this frequency range. Many manufactures are offering generous rebates on the purchase of new equipment if you return 700 MHz systems to them, but time is running out, so better now than later.

Myth #2: I heard the FCC is making wireless microphones illegal. Can they do that?

First of all, within certain boundaries, the FCC can do anything it wants! Many users of wireless equipment in general fail to understand that purchasing said equipment does not guarantee you the right to operate it in perpetuity. By purchasing the equipment, you are not purchasing a license to use the frequencies the systems operate on. Some devices require licenses in order to operate, some do not (more on that later). If the FCC decides to change the rules in such a way that it would make it illegal to operate your system, they can do that.

That said, the only wireless microphones that are now illegal to use are ones that operate in the 700 MHz spectrum, as outlined above. There has not been any indication from the FCC that they plan to further restrict wireless microphone operation in the remainder of the core television band (which now stands at 470 to 698 MHz, or TV channels 14 – 51). If anything, they’ve done the exact opposite. Also back in January, the FCC issued another report and order that essentially reclassified wireless microphones that operate in the TV bands as “unlicensed” devices, according to the Part 15 rules. This statement may be confusing to those who don’t realize that prior to the January ruling, an FCC license was required to operate “low power auxiliary stations” (i.e. wireless mics, ears, etc.) in the TV bands. Wireless microphones were classified as secondary users, with primary users being the actual broadcasters. Furthermore, the eligibility requirements for a LPAS license were fairly restrictive, meaning that a large number of wireless microphone users who may have wanted to get a license weren’t eligible anyway. In recognition of the realities of the current situation, the recent FCC action allows anyone who uses or plans to use a wireless microphone the ability to do so, without any concern of operating illegally, and without the need to obtain a license. For those users who are able to obtain a Part 74 license (referring to the rule part that governs secondary usage of LPAS), that is still an option. It is important to note that these rules are considered “temporary” as the FCC considers the future of the broadcast television spectrum. To help ensure that wireless microphone users are apprised of the situation, the FCC has issued a consumer alert that must be displayed on wireless microphones operating in the broadcast bands. Please note, manufacturers must place this text on the outside of the box, but anyone who sells a wireless microphone is also responsible of displaying this notice at the point of sale.

Consumer Alert: Most users do not need a license to operate this wireless microphones system. Nevertheless, operating this microphone system without a license is subject to certain restrictions: the system may not cause harmful interference; it must operate on a low power lever (not in excess of 50 milliwatts); and it has no protection from interference received from any other device. Purchasers should also be aware that the FCC is currently evaluating use of wireless microphone systems; and these rules are subject to change. For more information, call the FCC at 1-888-CALL-FCC (TTY: 1-888-TELL-FCC) or visit the FCC’s wireless microphone website at www.fcc.gov/cgb/wireless microphones.

There are a few key points here. Most importantly, notice that using a wireless microphone without a license means you are not entitled to any interference protection. Secondarily, you may not operate at power levels above 50 mW. This last point is a good reason for obtaining a Part 74 license; with a license you can operate up 250 mW, the maximum allowed by the FCC for wireless microphones. Obtaining a license as a secondary class user also affords a greater level of interference protection (vs. “none” for unlicensed users), which could be important when and if the unlicensed “white space” devices come to market. More on that next time… In the meantime, rest assured that as long as your wireless microphone does not operate above 698 MHz, whether you have a license or not, you are legal.