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Brother, Can You Spare a Frequency?
By: Carl Cordes

The economy is not the only place where you may experience some belt tightening over the next several months. The available UHF spectrum for wireless microphones is shrinking, too. The DTV transition, 700MHz spectrum auction and rules allowing new transmission devices in unused UHF channels have converged to make life a bit harder for wireless microphone users. While your equipment will not suddenly stop working, knowledge of the facts and a review of the frequency range of your equipment is essential to cope with the changes. Prudent selection of new or replacement wireless is more important than ever, whether you use one channel or 100 channels in your church.

It started with the push in the late 1990s to change television broadcasting from its traditional analog format to the high-resolution digital format commonly referred to as DTV. The characteristics of DTV vs. analog TV signals allow channels to be more densely grouped in a given market, which resulted in a plan to reduce the total number of available television channels in the UHF band. Congress mandated that the FCC auction off the "extra" channels no longer needed. AT&T, Verizon, and others paid more than $19 billion last year for channels 52-69 (698MHz to 806MHz) for broadband, cell phone, video streaming, and other telecommunications services. Also, a portion of the spectrum was reallocated for public safety use by police, fire, medical, and disaster response. 

In August 2008, the FCC proposed a rule change prohibiting all Part 74 devices (this includes wireless microphones, intercom, and in-ear-monitors) in the 700MHz band as early as February 18, 2009. As of this writing, the final rule, and thus a specific date, has not been issued. The new owners of the spectrum are urging the FCC to require Part 74 devices migrate out of the spectrum no later than February 18, 2010. It is not a question of IF a ban will be imposed but WHEN. Technical presentations to the FCC have indicated there is a strong possibility of interference between Part 74 devices and the new commercial and public safety uses.

If you have equipment in this spectrum, there are several reasons you should be migrating out of the 700Hz band at your earliest opportunity. 1) You do not want to risk interfering with public safety life-saving operations 2) Most 700MHz gear for the U.S. market is outdated and you will benefit from new features and bandwidth. Many manufacturers are also offering trade-in rebates or re-banding services. 3) Replacement parts are already becoming obsolete as reputable manufacturers curtailed or eliminated U.S. models operating in this range two or more years ago. 4) The financial impact will be immediate if you wait till you receive interference or a "violation" notice. Planning, budgeting, and replacing over the next few months will mitigate the burden on church finances.

I often get asked, "Will the FCC really come looking for devices operating in the 700MHz band?" The short answer is YES. Unlike other countries, the FCC does not have a fleet of detector vans searching cross-country for violators. Enforcement will mostly be based on complaints received from the new owners of the spectrum. The FCC already has a presence at major events, so it is reasonable to assume they will be monitoring the 700MHz band for unauthorized use. The FCC can also utilize selective detection/enforcement localized around a geographic or high-profile area. It is extremely important to understand that FCC fines are steep, typically starting at $10,000. Should you ever find the Enforcement Bureau knocking on your door, you are well-advised to cease doing whatever brought them there and avoid a repeat visit.
An example of the interference problems you may encounter in the 700MHz band already exists. Qualcomm bought TV channel 55 (716-722MHx) nationwide in a previous auction and has already deployed a video streaming service call Media Flo or Flo TV in 40+ cities/areas. That number is likely to double by the end of 2009 and significantly increase coverage in 2010. Other users of the spectrum are expected to deploy similar broadband transmissions that if it is close enough and strong enough, you will not find a usable frequency in that channel.

Most users with 700MHz band equipment have upgraded or will upgrade to equipment that operates in a portion of the remaining UHF TV channels 14-51 working around DTV signals. Planning and research by you or a company well-versed in RF issues are essential to getting the right frequency range for your church location. Many church campuses expanding or building new facilities now include an RF Sweep in the design process. This identifies specific sources of potential interference penetrating the confines of your sanctuary or classroom. This data is then used to establish a band plan for the facility. Establish a realistic budget for your wireless equipment. Cheaper is definitely not better. Cheaper will have fewer frequencies, be more susceptible to interference, have shorter range, and have limited repair options. A key consideration to your system selection will be the type of front-end filtering it employs. A tracking filter scheme is more expensive but provides better results.

Good remote antennas and antenna coax are also important to getting the best coverage out of your systems. I recommend you not use the whip antennas that came with the system if you have four or more channels of wireless. Upgrade to an antenna distribution and you will upgrade to better RF. An important note for those with 700MHz equipment currently using antenna distribution and active antennas—they may be frequency specific and will need to be replaced, too. By following these guidelines, you are positioning your RF equipment to deal with the next spectrum threat – The White Space Devices (WSD) or Television Band Devices (TVBD), as they now want to be called.

The FCC has established the rules for the new TVBD broadband devices that will operate below 698MHz in the second report and order of ET Docket NO. 04-186, "Unlicensed Operation in the TV Broadcast Bands." Petitions and lawsuits are in play now to change the rules and no new device is ready for certification or sale. So, it is premature to get too in-depth in this article. Suffice to say, there will be more competition for spectrum next year or the year after. But the rules as they stand now offer hope that some level of protection will be given to existing wireless microphone users.

Carl Cordes is general manager of Professional Wireless Systems, www.ProfessionalWireless.com.









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