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Once analog TV transmissions cease, it’s going to be a different spectrum landscape for the makers and users of wireless microphones and intercoms.

When the DTV transition ends February 2009, the 700 MHz band will no longer be available, as the FCC has plans to reallocate channels 52 to 69 (698–806 MHz) for other services, and may even put them up for auction.

“In many ways, this is a continuation of spectrum loss that began with the introduction of DTV several years ago,” said Karl Winkler, director of business development for Lectrosonics, a developer of wireless mic and audio processing systems based in Rio Rancho, NM. But at least that’s a given.

What’s still up in the air is what’s going to happen to the so-called white space channels. White space is a term that has developed to denote TV channels that won’t be allocated to a particular station in a given market when analog transmissions are turned off. The FCC is considering allowing both fixed and unlicensed wireless consumer personal portable devices in these bands, and Congress has gotten in the act as well, with competing bills in the House and Senate.

Proposals for fixed frequencies are geared towards providing rural broadband, while personal portable use could include such consumer wireless applications as computer networking, cell phones, and personal digital assistants. Currently, many of these products operate in other RF bands, such as 2.4 GHz.

“The bottom line is that less spectrum will be available, and the general RF noise floor will be higher than it is now,” Winkler said. “This will change the number of wireless channels that can be operated simultaneously in some markets, and it will also likely reduce the range of many wireless systems.”

Makers of wireless pro audio systems are not taking this situation lightly. They’ve been proactive on two main fronts—working to sway policy makers to achieve a favorable outcome as they see it, and developing new products and technologies or modifications to existing ones to work in the new milieu.

New Products Address White Space IssueNEW YORK
Even as they lobby Congress and the FCC, wireless mic and intercom companies are increasing their R&D efforts for new products and technologies that could work around potential white space problems. A few of these have been announced.

Audio-Technica introduced at InfoComm 07 its SpectraPulse Ultra Wideband (UWB) wireless microphone system that transmits signals using a series of short nano-second pulses which occupy an instantaneous bandwidth of 500 MHz within the 6 GHz frequency spectrum (see “Audio-Technica Launches UWB Mic System,” Aug. 22). The first product, geared towards boardroom and conference room applications, is audio bandlimited to from 100 Hz to 12 kHz, but Steve M. Savanyu, marketing manager for broadcast, theatre, installed sound for Audio-Technica U.S. said that future generations of UWB products from the company will have the specs that broadcast and live sound applications require.

This system bypasses any white space problems by operating on a non-white space frequency, and the nature of the transmissions makes it less susceptible to either causing or receiving interference to other RF devices.

Lectrosonics is developing new technology that will sidestep the white space problem, as well, according to Karl Winkler, director of business development for the company.

“Existing products will be made in new frequency bands that don’t appear to be affected by the spectrum loss,” he said. “Our products have always been very selective at the receiver, and our higher-powered transmitters work well even with a fairly high noise floor. These things will be advantages to users as the spectrum continues to shrink.”

By the end of the year, Lectrosonics will introduce several new transmitters (UM450, SMA, SMDA, SMQA), IFB systems (IFBT4, IFBR1a) and the Venue modular receiver system for the 944-952MHz band.

“Other new technology will be a digital modulated wireless system operating in the ISM band between 902-928MHz,” Winkler said. “That’s about all I can say about it at the moment.”

Avoiding both the white space frequencies and the 700 MHz band, Clear-Com has two product lines for wireless intercom.

The CellCom series operates in the 1.9 GHz band and employs digital enhanced cordless telecommunications (DECT) technology that’s similar in operation to cell phones. The Tempest 2400 is a digital wireless intercom system that currently operates on the 2.4 GHz band, but in early 2008, a version will also be available for the 950 MHz band, according to Ed Fitzgerald, director of North American sales for Clear-Com in Alameda, Calif.

Ciaudelli from Sennheiser said he couldn’t be too specific about new products and technologies at this time, but provided some hints.

“You’ll see more efficient use of available spectrum and better equipment that will aid end users in choosing available frequencies,” Ciaudelli said. “These products will find free frequencies and self-coordinate with other channels in the system.”

At the same time, “there’s no magic bullet,” he added. “We’ll look at other areas of operations, but there’s a reason why TV broadcasters and wireless mic users are in the UHF band. The propagation characteristics are very good. If you use a different band, you’ll need more power, or if you use lower frequencies, you’ll need a larger antenna.”

As for Shure, Brunner said, the company “is exploring all of the technical options in an attempt to be prepared for whatever the future landscape holds. While most of the pro audio wireless manufacturers may be exploring other technical options or are planning modifications to current products, it’s hard to do with certainty until we know what the landscape will be. The FCC ruling will direct future products and designs developed by the pro audio community and the consumer personal portable community, and will determine the magnitude of the challenge.”


A key strategy is to educate regulators and legislators that the TV spectrum isn’t as “white” as some may like to think. Shades of gray may be more like it, especially in spectrum-congested metropolitan areas.

“The term white space is born out of a fundamental misunderstanding that the space between TV channels is unused,” said Mark Brunner, senior director of public and industry relations for Shure. “Those in pro audio know that it’s not. Metro areas could suffer the most if unlicensed wireless consumer personal portable devices are allowed to operate. There are little or no available channels left in the first place, and the sheer population of these areas almost guarantees large usage of such devices.”

Shure has been engaged with this issue for nearly four years. “It’s been a long haul, but we felt early on that it was important to take a leadership role in this issue,” Brunner said. “This year especially, Shure has been very active in meeting with the FCC about the complexity of wireless usage in pro audio applications. We have enjoyed a good longstanding relationship with the FCC and we have worked very constructively with them on this topic.”

Part of the urgency is that per the FCC’s timetable for Docket 04-186, the commission plans to issue rules for so-called white space devices this October. Meanwhile in Congress, one bill, H.R. 1597, proposes to speed up the authorization process, while another, H.R. 1320, proposes to take things slower, and not allow portable wireless devices until three years after fixed devices have been operating without interference. This bill also stipulates that new portable wireless devices not interfere with existing users. The Senate too has taken up the issue with S. 234 and S. 337. At this writing these bills remain in committee.

Shure has filed several formal comments with the FCC, assembled a coalition of industry wireless users and providers to provide comments to the FCC and legislators, and is a member of two IEEE work groups related to this issue.

According to Brunner, Shure joined these groups to help represent the interests of incumbent TV spectrum users and to develop a standard that will help prevent interference to wireless microphones.

In addition, Shure received a Part 5 experimental license from the FCC and a special temporary authorization to conduct interference tests using a simulated wireless broadband signal in the TV band. Shure presented the results of these tests to the FCC and gave live demonstrations to House and Senate staff members, according to Brunner.

Sennheiser is participating with industry groups, channeling their comments and evaluations of proposed technologies for wireless personal portable devices through those groups. Sennheiser successfully persuaded its congressman, Joe Courtney, a Democrat representing Connecticut’s Second District, which includes Sennheiser’s headquarters in Old Lyme, to add his name as co-sponsor of the house bill (H.R. 1320) that is favorable to incumbent wireless users on the TV bands.

“We feel this [H.R. 1320] is a very intelligent approach to allow technology to move forward and not wreak havoc with existing systems,” said Joe Ciaudelli, industry team manager professional products, Sennheiser.

Sennheiser has been encouraging people to write their own legislators about this issue, even providing a letter template. “White spaces started with the idea that we need to bring broadband into rural areas, but the way the white space legislation is currently written, it goes way beyond broadband to rural areas,” said Volker Schmitt, senior applications engineer for Sennheiser.


Fixed broadband service to rural areas isn’t a major issue for incumbent wireless users since they would be fairly easy to frequency coordinate. But the random nature of transmissions from personal portable devices wouldn’t allow for such coordination, and one huge concern is they could cause interference to incumbent users and at the most inopportune times.

Sennheiser is “communicating with legislators making them aware that the term ‘white space’ is a misnomer since broadcasters, film producers, and professional entertainers have been using licensed devices, such as wireless microphones and monitoring systems, in this spectrum for years,” Ciaudelli said. “Major news, political, sports and entertainment events would not be able to operate reliably if the spectrum was randomly flooded by new unlicensed devices.”

To address this concern, the FCC could require personal portable devices to incorporate various technologies like a listen-before-talk function, a geo-location database, and a local beacon device.

But Schmitt cautioned that “these devices are vaporware and undefined. That’s why creating legislation before the devices are truly defined is setting a really dangerous precedent.”

Sennheiser is investigating and consulting on proposed solutions and compromises for coexistence with new devices, according to Ciaudelli. “Each of these solutions has merit. However, we are trying to develop an optimized proposal with other industry leaders that is both economically and technically feasible,” he said.

Early test results haven’t been encouraging. In late July, the FCC Office of Engineering and Technology issued test results for two submitted prototypes, not actual consumer products, of personal portable devices (see “Devices Fail FCC White Space Tests,” Aug. 22). The report concluded, “the sample prototype… devices… do not consistently sense or detect TV broadcast or wireless microphone signals. Our tests also found that the transmitter in the prototype device is capable of causing interference to TV broadcasting and wireless microphones.” Brunner noted that this emphasizes the need for testing of any new device in real world situations to see how they affect incumbent users.

“Without demos,” he said, “the FCC should proceed cautiously.”