Tuesday, August 26, 2008

White Spaces Debate Outs Wireless Mics

One perhaps unexpected consequence of the increasingly heated discussion over the "white space" TV band spectrum is the outing of "unauthorized" wireless microphone users, such as churches, theaters, corporate lecture rooms and so on. It turns out that many of them have been squatting on unused UHF TV channels for years with nobody being the wiser. Now they'll have to vacate or risk being crushed like bugs by the winners of the 700 MHz spectrum auction when new services start moving into the old analog TV channels next February. What's more, it's becoming increasing less likely that they can simply re-tune their transmitters and quietly slip down into gaps between the new digital TV (DTV) channels.

Wireless microphones are one of those clever technologies that have become insidious over the years. You see them everywhere there is any type of vocal performance. Those microphones you see on televised concerts that don't seem to have any wires connected? That's them. A lot of times you don't even notice the mics. Ever see a microphone pointing at someone on a TV news show? The host and the guests are just chatting like they were in your living room, but you never hear any background noise. They're wearing wireless microphone packs with tiny mics on their lapels. Broadway shows are also extensive users of wireless mics, so that you can hear every nuance of the performance without the actors having to scream. Even your pastor may be using a wireless microphone on Sunday to be able to move around during the sermon.

So if this technology is so insidious, what's the problem? It seems to work just fine. Yes it does, but what you don't realize is that the frequencies many of those wireless microphones are transmitting on are supposed to require a government license and are only for specific types of users. They are regulated as low power auxiliary stations under FCC rules Part 74, subpart H. The key word is "stations." These devices are considered to be lower power radio stations. This part of the rules covers broadcasters, and these auxiliary stations are supposed to be for the use of broadcasters, radio and TV networks, movie and TV program producers, local distribution networks, and cable system operators that produce their own shows.

Oops! No mention of churches, theaters, schools, concerts, lectures, dance clubs, performing arts centers or the like. Yet, they all use wireless mics. So why hasn't the long arm of the law come after them? Mostly because they haven't been causing a problem. There was so much unused space in the UHF TV bands and these devices run such low power that there just wasn't an interference issue. That's about to change.

First thing that will happen is that the new owners of the upper UHF TV channels from 52 to 69 will move in with high power equipment for mobile broadband and other services. Considering the billions spent to gain this valuable spectrum, the chances of large blocks staying quiet are about nil.

On top of that, Google is mounting a public relations campaign called "Free The Airwaves" to drum up support for turning the remaining white space spectrum between DTV channels into unlicensed usage across the board. That would legitimize the continued use of wireless microphones for all performers, but interject the new problem of interference and lots of it.

So what's a poor wireless mic user to do? There are some other frequencies already available for this use. But "broadcast" quality equipment, especially systems that can support many simultaneous microphones, is scarce and unused channels even harder to find. There's also the issue that thousands, perhaps as many as a million 700 MHz wireless microphone systems are already in the field and will be inconvenient and expensive to replace. That argues strongly for protecting at least some of the new DTV spectrum below 700 MHz for wireless microphone usage. Perhaps a good long term solution could be found like the creation of the Wireless Medical Telemetry Service for hospital equipment that might otherwise be a white space squatter.

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