03.13.2007 08:00 AM
Originally featured on BroadcastEngineering.com
Bill to protect wireless mics advances DTV protection effort

Congressman Bobby Rush, D-IL, introduced a bill March 5 aimed at protecting users of wireless mics from harmful interference that could be generated by proposed unlicensed consumer electronics devices that would share TV channel spectrum.

H.R. 1320 acknowledges that introduction of such devices "without adequate safeguards" would interfere with "other existing television band devices already operating on the unassigned, non-licensed television channels." It further states that these existing devices "require protection to preserve their important operation."

The bill outlines requirements for the FCC to follow in allowing such devices to be used, including:

  • Limiting operation to fixed locations in rural areas;
  • Allowing operation on unassigned, non-licensed TV channels between 54MHz and 698MHz; and
  • Permitting no such use before Feb. 17, 2009.

It also spells out how the commission must protect wireless mics and other such devices from harmful interference generated by these new devices. Steps include:

  • Certifying that these unlicensed devices have successfully completed lab and field tests by independent labs demonstrating that they do not cause interference to low-power auxiliary devices like wireless mics;
  • Preventing these devices from operating on channels used by incumbent certified low-power devices; and
  • Consideration of other ways to protect incumbent certified low-power devices, such as reserving TV channels for their exclusive use.

The bill gives those concerned about protection of wireless mics a voice in the debate in Congress over the unlicensed TV band devices, said Jeff Krull, VP of product development for Shure. The company, which has taken a leadership role on the issue, is “engaging” other Congressmen, seeking additional sponsors for the Rush bill.

Key to the argument of those wishing to allow the use of unlicensed TV band devices is the ability of “smart technologies” to detect the presence of other frequency users, like wireless mics, IFBs and DTV signals, before transmission. If a particular channel is being used, the TV band device looks for an unoccupied slice of the TV band to use before transmitting.

Smart technology doesn’t yet exist, however, so it’s not proven, Krull said. Additionally, even when it does, there’s no guarantee that it will be effective in detecting wireless mic use. “Wireless mic operation is fairly intermittent,” he said. As a result, smart technology could miss the presence of wireless mic operation, commence transmitting and cause interference. He also questions how good TV band devices will be at detecting the presence of wireless mics and other devices.

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