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by John Carlson, Systems Engineer, Sound Vision, Inc.
If you're like many wireless mic users, you've been reading stories about the reassignment of the analog TV frequency spectrum with some dismay. When analog broadcast TV shuts down (now delayed until June 12, 2009), a large number of "white spaces" will disappear – that is, unused TV channels that the audio industry has used for at least 20 years to carry wireless mic signals.
On November 4, 2008, the FCC finally announced their decision about how these portions of the spectrum will be managed. The bad news is that many wireless mic systems will eventually have to shut down.
There is good news, however, and this news is much better than what many feared.
- The FCC will accommodate wireless mics in the future, and the new FCC regulations appear to be practical and well-considered.
- At least half of existing wireless mic systems should be fine.
- Most of the systems adversely affected will not need to shut down immediately.
Since the decision affects so many Sound Vision clients, we want to make sure you understand it and what it will mean to you.
Background
The issues we're facing today have their roots in the 1930s, when the Federal Communications Commission began to assign licenses for broadcast television. Given the technology of the era, adjoining frequencies could not be assigned in the same geographical market because of the possibility of interference from one station to the next. So channels 2, 5, 7, 9, and 11 might be assigned for VHF broadcasts, but 3, 4, 6, 8 and 10 would not. When the first UHF channels went on the air in 1949, more "white spaces" in the spectrum were left open.
Fast forward to the 1980s, when wireless microphones were being perfected. The audio industry, with the FCC's consent, began to take advantage of these white spaces to carry microphone signals.
When the FCC announced the move to digital television, it consolidated the broadcast spectrum, leaving what became known as the "digital dividend," the frequencies between 698 and 806 MHz, free for other uses. With digital technology, there was no longer a need to keep TV stations off adjoining channels, and though some white spaces would still exist, the UHF spectrum could be cut approximately in half.
Unfortunately for mic users, the FCC took more than ten years to decide how the digital dividend would be used, eventually auctioning the "700 MHz band" in April, 2008. When it became clear that mic users would no longer have access to these frequencies, manufacturers stopped supplying systems using them. But that was not until the spring of 2007.
By the end of that year computer equipment manufacturers were lobbying to use the remaining white spaces for new broadband Internet and portable communications devices. The audio industry, in turn, lobbied to ban these devices, fearing they might create so much interference that wireless mics would not work at all. This controversy was not resolved until the FCC announced its decisions on November 14.
Some of our customers have asked why the audio industry continued to make UHF microphones at all when it was obvious that something was going to change. The problem was, and is, that the industry operates under the guidelines of the FCC. Until they knew where they would be allowed to operate, it was impossible to make any decisions about what to manufacture. Only now that the FCC guidelines have been announced can the industry move forward with confidence.
The FCC decisions
To understand how your wireless mics may be affected, it's important to realize that there are two parts to the FCC decision affecting different sections of the spectrum.
First, AT&T, Verizon and some smaller telecommunications companies have licensed the 700 MHz band, UHF channels 52-69, for digital network devices. They have exclusive rights to these frequencies.
Second, unused portions of the remaining television spectrum, which will vary from city to city, will be available to a number of different types of user. These include the frequencies 55-72 MHz, 77-88 MHz and 175-216 MHz in the VHF range plus 512 to 698 MHz, or UHF channels 21 through 51. These frequencies will be used by new "white space devices" in three ways.
- New mobile network devices, such as cell phones and wireless cards for laptops, will communicate in certain UHF frequencies.
- In Chicago and 12 other cities, open frequencies in UHF channels 14 through 20 will be dedicated to public safety use by police and fire departments.
- Digital broadband services will be allowed to operate in UHF and VHF frequencies. These will offer fixed point-to-point communications between antennas with a range of several miles and homes and businesses.
How these changes will affect you
According to Chris Lyons, Manager of Educational and Technical Communications at Shure, it's a little unclear how users of 700 MHz mics will be affected.
"The FCC is saying they want wireless mic users out of the spectrum quickly, but we don't believe AT&T or Verizon will be ready to operate before the end of 2009 or longer." Most likely if you have 700 MHz mics, they will continue to operate for several months at least, but you will need to shut them down eventually.
For mics operating in channel 51 or lower, the news is much better. The FCC announced that a new online database will be set up to keep track of the users of various frequencies, and that new white space devices will be required to check with this database at least daily to make sure that they don't interfere with others. Owners of existing wireless mics will be able to register their systems and thus reserve the channels they use for their particular geographic area.
"This is a great solution," says Lyons. "A church will be able to say, ‘hey, we're using these channels, and they would be off limits for any new devices."
The FCC will require the portable devices to include a GPS circuit, so that they can access the correct portions of the database to avoid interfering with local users. "They will also scan the various frequencies as a secondary protection," Lyons adds. "So even if you're not in the database, they will hopefully detect your microphone and avoid that channel."
In most cities there will be a few empty channels where there are no digital white space devices at all. "For people who don't need too many wireless mics –less than 20, say– they can just operate in those channels, ignore the database and not worry," Lyons explains.
No doubt there will be some rough spots. For example, organizations located in areas where TV transmissions from two different cities overlap are already having problems finding open channels. That issue should improve in June when analog stations go off the air, but some re-coordination of frequencies may be necessary. In any event, Lyons says that "the decision is favorable enough that we believe there will be plenty of operability for wireless mics for the foreseeable future."
Help in this transition
Several manufacturers are considering trade-in programs to help users who have microphones that will no longer be operable. "We have announced a rebate program at Shure," Lyons says, "because we hope that people will buy some new gear now and minimize the problems they may have later."
The Shure program offers a trade-in credit of up to $1,000 for any Shure 700 MHz wireless mic system purchased before February 1, 2007, when Shure stopped regular sales in these frequencies. They also offer a smaller trade-in on most 700 MHz systems from other manufacturers. The amount of credit varies with the new system purchased, with a higher value applied to gear traded for costlier Shure systems.
In addition, various manufacturers are looking at different spaces for new wireless products. One or two have introduced 2.4 GHz spread-spectrum products. Audio Technica is offering a system based on UWB or Ultra Wide Band technology, which operates in the 6 GHz band using a series of digital pulses. Lyons says that Shure believes the UHF frequencies will continue to be the best option, but they are working on ways to improve their UHF microphones. "We will put more effort into squeezing more frequencies into fewer TV channels, so our products will operate even more efficiently than they do now."
Sound Vision remains committed to helping you get through this transition as smoothly as possible. We can't make this go away, but we can help in most cases. For example, we can come out to your location with our RF spectrum analyzer and find out what frequencies are available for microphone use. When the FCC announces how to register on their new database, we expect to be able to provide that information or handle the registration process for you.
For now, the best thing you can do is to simply identify which channels your mics are using. If you have systems in the 700 MHz range, you should start thinking about how and when to replace them. If your mics are using frequencies below 698 MHz, hopefully you're in good shape, but it is possible that you will need some help with them in 2009.
If you're having any issues with or questions about your mic systems, please call us and we'll do our best to help.
Read the Shure White Space FAQ for more details
Read the text of the FCC November 4 order regulating white spaces
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