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Four Keys to Success in a Crowded UHF Broadcast Band

Are you ready for the future of wireless microphones?

Alex Milne

The official goal for the FCC incentive auctions is now the middle of 2015. A lot of ink has been spilled on doomsday scenarios for wireless microphones.

These are four ways to make spec’ing and installing wireless audio equipment easier and faster in the new, much more crowded UHF broadcast band that’s just around the corner.

Use Wide Band UHF Microphones

Many manufacturers currently sell wireless microphones tuned to sets of frequency blocks located somewhere within the larger UHF band. They allow the user to purchase a block that has the most available frequencies in their area without needing to program channels throughout the entire band.

After the auction, UHF spectrum will shrink and remaining spectrum will become much more crowded. Available channels will be spaced farther and farther apart, and a narrow band may limit the flexibility of channels available. As such, wider band systems will be an advantage and we may even see the old block system phased out.

Approach Other Bands, Especially 2.4 GHz (WiFi), with Measured Caution

Extreme congestion in UHF may precipitate a move away from UHF into other bands, like 2.4 GHz. But the entire spectrum is crowded and no band is future-proof. Careful research on the spectrum in your area alongside collaboration with other wireless users in the building is recommended before purchasing first generation systems using unconventional frequencies.

2.4 GHz is especially vulnerable in corporate environments. WiFi (which uses 2.4 GHz) is ubiquitous and hotel conference rooms, board rooms, and entire business campuses are installing powerful WAPs that can and will interfere with 2.4 GHz microphones.

Use Directional Antennas and Place Antennas Wisely

After the auction some percentage of integrators will suddenly find receivers with stock whips are more prone to interference than they were before. Whip antennas have a coverage area that extends in all directions, raising the probability of interference. Directional antennas allow a larger number of wireless devices to coexist inside a given venue by controlling and focusing coverage.

Related: Spectrum Changes Pose Major Threat to Wireless Microphones

Integrators will need to move antennas out of the AV closet and into the presentation space itself. Once in the space, wall mounted directional antennas can establish line-of-sight and focus reception away from extraneous signals and toward the microphone. If directional antennas are not possible due to architectural restraints, moving the receiving antenna as close as possible to the microphone and reducing transmitter power using attenuators will create a sufficient signal-to-noise ratio. 

Analyze Spectrum Before Installs

The number of competing signals in the new UHF will be higher and their distribution more complex. Integrators will save time by using spectrum analyzers to visualize the radio spectrum and locate open channels before making the decision on which microphone is best suited for the install. Using TV station databases or tuning the receiver to the first clear channel was never ideal, but after the auction that may be totally ineffective. Spectrum analysis also facilitates intermodulation distortion calculation and correction, a necessary step in setting up systems with multiple channels.

Spectrum analyzers designed for research and telecom fields are expensive and contain features that few commercial AV integrators will ever need. But there are some analyzers within reach of even small firms.

One portable model, for example, is the RF Explorer. It establishes an RF visualization for installs, as well as diagnoses wireless interference cropping up on existing installs. RF Venue manufactures a rack mounted unit designed for commercial audio installations to manage and monitor RF conditions on an ongoing basis.

 

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