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Sound Advice

Wireless Microphone System Frequency Coordination & Planning Primer BY Colin Bernard


When I was first approached to write this article, I must admit my mind did reflect back to the late ‘80s and early ‘90s. During this time, sound designers of mainstream theatre musicals had just started using 24-channel systems that I, as the supplier, was ultimately responsible and on the hook for if they experienced RF interference.That was considered a lot of wireless channels in those days; however, we did have the luxury of a lot more of the RF spectrum being available, utilizing the VHF band and then migrating to the UHF 470-698 MHz and 698-806 MHz bands.

The next challenge with which I was involved was in 1993 – a major 32-channel musical which toured 20 US and Canadian cities including Broadway in New York and then ventured to Asia. During that era, this production would not have been possible without large chunks of TV “white space” being unoccupied. Several North American productions touring with 48-channel systems were next to depart our shores. They were crazy times, with some systems moving every six weeks!

How time flies, though. It’s now 23 years later and the spectrum landscape certainly has changed quite substantially with the Federal Communications Commission (FCC) in the US outlawing all use of wireless microphones in the prime real estate range of the 698-806 MHz bands. Additionally, the FCC has adopted new rules and opened opportunities for new unlicensed “white space devices,” or TVBDs, for future use in the 470-698 MHz TV bands while establishing essential protections to prevent interference and disruption to important incumbent services, including broadcasting and wireless microphones.

Industry Canada is yet to rule on this issue and has been conducting consultations, for which I was one of many parties that were contacted. In January 2010, Industry Canada permanently allocated the UHF chunks 764-776 MHz and 776-794 MHz for “exclusive public safety use.” As a result, no wireless microphone users were permitted to operate in that range as of March 31, 2011.

In the remaining UHF bands (698-764 MHz and 776-794 MHz), “these devices will be allowed to operate until a later date, which will be announced by the department” states the January 2010 document. No more wireless mic device certifications in the 698-706 MHZ bands have been permitted in Canada as of that date.

So here we are now in June 2012. Monopolists like the Googles and Microsofts of the world have their eyes pinned on the 470-698 MHz “beachfront property” for possible use for new wireless “SuperWiFi” white space device usage. This range of frequencies provides good propagation characteristics with low power and practical antenna sizes for these types of future devices. Today, Industry Canada informs me they expect to inform the industry of “their firm policy decision on future TV white space activity in the summer of 2012 in respect to the 470-698 MHz frequency band.”

With respect to the below 698 MHz analog to DTV transition in Canada, most major broadcasters in the urban population centres in Canada have completed and vacated their temporary DTV test transmission channel assignments and are now permanently broadcasting in digital, mostly on their original “old” analog TV channel allocations. In some cases, this shifting has freed up some previously occupied TV channels for our use.

In dealing with these ongoing shrinking RF spectrum challenges, manufacturers are utilizing high-end, very sensitive selective receiver technologies that utilize extensive front-end filtering combined with frequency agile transmitters that incorporate variable power. Receivers with built-in scanners are a great tool when in a pinch on location and useful if ever in the need to get out of trouble.

Utilizing intermodulation analysis software frequency coordination programs and portable RF spectrum analyzers, there is a growing need for qualified Frequency Coordinators. The coordinators are punching out many more compatible frequencies than they did 23 years ago, as the growing demand for more and more IEMs and IFBs including communication systems continues, pushing some productions to the limit.

If you plan on expanding your existing set-up or purchasing new systems, you need to be aware of the potential for outside interference; however, with thorough initial planning/scanning and more and more readily affordable frequency coordination programs like IAS and RF Guru coming to market, creative productions using more and more wireless devices will prevail!

[i]Colin Bernard is an industry veteran with 23 years in pro audio in Canada and seven years prior to that Managing Sennheiser South Africa followed by a stint managing the Pro Audio Dept of Neumann and Sennheiser in Canada. As the Director of Canadian Operations of Lectrosonics Canada since 2006, Colin specializes in supporting all aspects of the design, sale, deployment, and implementation of wireless microphones, IFB, IEM, and DSP automixer systems in the broadcast, film, theatre, staging, touring, and AV markets. He is always willing to discuss and help out with RF management, so you can contact him at 416-768- 2220 or [url=mailto:colinb@lectrosonics.com]colinb@lectrosonics.com[/url][/i]

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