The FCC, DTV and Wireless Mics

This was something that I wasn’t aware of until this week. If anyone uses wireless mics for your group or church, you may need to adjust your frequencies after the DTV transition is complete. I’ll be honest and say that I know very little about sound equipment, so maybe some of you tech-heads can clue me in with further details about how the new DTV channels will affect wireless signals. Maybe this will at least make a few of you aware and give some insight on possible future techinical difficulties.

Here is a note from Shure that I found informative:

What Digital TV Means to Wireless Microphone Users
The introduction of Digital Television (DTV) service in the U.S. will result in more intensive use of all TV spectrum, both VHF and UHF, as new digital signals come on the air. In addition, the FCC has reallocated four UHF TV channels for use by Public Safety stations, and plans to auction off the remainder of the 700 MHz spectrum for other wireless services.

However, the FCC has ruled that wireless microphones may continue to use all presently unoccupied TV channels until the end of the DTV transition

Here is a brief summary of how the FCC plans to implement Digital Television service:

The FCC has established a “transition period” which will last through February 19, 2009. During this time, existing TV stations will be assigned a second TV channel on which they will begin broadcasting in the new digital format. This means that some television channels that are now vacant may be filled. Wireless microphones operating on these TV channels may or may not encounter interference from the DTV station’s signal.

During the transition period, public safety agencies will begin to use TV channels 63 – 64 (764 – 776 MHz) and 68 – 69 (794 – 806 MHz) for two-way radio communications. As these frequencies gradually become busier, wireless microphones operating on these TV channels may encounter occasional interference.

After February 19, 2009, TV channels 60 – 62 (746 – 764 MHz) and 65 – 67 (776 – 794 MHz) will be opened up for use by new commercial wireless services. Licenses for these new services will be awarded by competitive bidding. Some of these auctions have already occurred, but the winners will not be able to use this spectrum until it has been vacated by the television broadcasts.

Wireless microphones may continue to operate on all of these frequencies, just as they do now. However, wireless microphones that operate on frequencies above 698 MHz should not be used after February 19, 2009.

In order to determine which TV channels will be used for DTV broadcasts in your area, you may wish to refer to the FCC’s Sixth Report and Order; DTV allocations. A complete list of U.S. cities and TV channel allocations appears in the Appendix of this report, beginning on page B-6. This document can be downloaded from the FCC’s web site, at: http://www.fcc.gov/dtv. Additionally, the Shure Wireless Frequency Finder (www.shure.com/frequency) includes DTV channel listings for every city in the United States.

Users who experience interference from DTV will notice the same performance issues caused by other forms of interference, namely increased signal dropouts, decreased operating range, and undesired noises. Wireless microphones that are used indoors, with line-of-sight between transmitter and receiver, may operate normally depending on the strength of the interfering signal. Wireless microphone users who do experience interference (whether from a DTV station or another user) have the same option that has always been available: change the operating frequency of the wireless system. Frequency-agile systems can be retuned by the user; fixed-frequency systems, depending on their age, can be reworked by Shure’s Service Department at moderate cost.

Effective use of wireless microphones has always required awareness of the primary users (television stations, wireless data services, etc.) in a particular city or area. Knowing which frequency ranges are occupied in your local area will become even more important as use of the RF spectrum increases. Used knowledgeably, Shure wireless systems will remain valuable – and legal – audio tools for years to come.