Wireless Microphones Technology Showcase
May 13, 2011 4:50 PM, by Mark Johnson
Given the recent and ongoing changes in FCC wireless system legislation, those looking to buy any quantity of wireless systems would be well-served to do their due diligence prior to making a purchase and familiarize themselves with the current rules regarding wireless system usage.
Among other things, such as keeping up to date with the regulations regarding licensing, it’s also important to know just what frequencies are available for a given geographical area as mandated by the FCC . And it’s important to know what frequencies are available given the usage in the local area, say a 50-mile radius of the location.
Fortunately, many of the major wireless manufacturers offer tools—online and otherwise—to help with frequency availability and by posting or linking to the latest updates from the FCC . Many of the systems available have the ability to scan for clear channels. But for more indepth information about what the airwaves look like in your local area, there are professional services that will perform frequency scans. For those with a bent toward DIY , there are scanners available for purchase or rental. Whatever your fancy, with the wireless landscape in pretty much a state of flux for the foreseeable future, it’s a good idea to periodically run checks to see what’s happening in your geographical region.
What’s the frequency?
Beyond all of that, you still need to find a wireless microphone system that will suit your particular requirements. There are many options to choose from, and some manufacturers offer multiple types within their product lines. With the tightening of available UHF spectrum, manufacturers are producing products that operate in other areas of the UHF spectrum, such as the 900MHz ISM or in the 2.4GHz bands. There are, of course, VHF systems that function in the frequencies below 300MHz, as well as systems that operate in the SHF frequencies above 3GHz. While the bulk of the systems available are analog UHF systems, some manufacturers have invested in digital transmission technology. Infrared (IR) technology is also available in some systems.
Frequency allocation in the UHF range is broken up into TV channels 14 through 51 (470MHz through 698MHz); what is now known as the 700MHz band (698MHz through 806MHz) for digital services and public safety; the 900MHz ISM band (902MHz through 928MHz) named but not limited to applications for industrial, scientific, and medical usage; and the 2.4GHz band (2400MHz through 2483.5MHz) for Wi-Fi and Bluetooth devices.
Each of the technologies carries its own set of strengths and weaknesses. For example, IR transmission can be very secure (the signal cannot be transmitted through walls); however, it requires a clear line of sight between the transmitter and the IR receiver. So it’s a good idea to be clear regarding what your particular goals and needs are in a wireless system. Again, manufacturers’ websites and customer support lines can be a great resource in helping to determine what type of system will serve you best. Since only an example or two from each manufacturer is highlighted in this article, be sure to check the websites listed for additional models and systems.
AKG offers the WMS 4500, which features an integrated data interface for PC controlling and monitoring. Also featured are AutoSetup, Environment Scan, and rehearsal functions. Transmitters can operate for up to 15 hours on AA–size batteries or 12 hours with optional rechargeable battery pack.
The company’s DMS 700 digital microphone system features proprietary signal encryption and 40 preprogrammed frequencies and the ability to operate up to 100 channels simultaneously. Low-cut filter, three-band EQ, and dbx compressor/limiter are integral.
Audio-Technica makes a couple of transmission choices available with its SpectraPulse Ultra Wideband technology—which operates outside of the TV channel spectrum— as well as UHF systems. The SpectraPulse system includes the drm141 digital receiver module, up to two aci707 audio control interfaces, and up to 14 mtu101 or mtu201 microphone transmitter units.
Also available from Audio-Technica, the 5000 series UHF system features a dual receiver configuration, IntelliScan automatic frequency scanning, and Ethernet 10BASE -T data/control connection for remote computer monitoring and control.
The RAD-360 wireless microphone system from Audix is a UHF system that operates between 614MHz and 662MHz with 193 selectable frequencies (per system group of 24MHz, spaced 125kHz apart). The handheld transmitters feature a -6dB, -12dB, or -24dB pad and can use interchangeable microphone head assemblies from Audix’s OM series.
Taking a different tack, Azden’s IR-CS infrared classroom system comprises the IRR-30P receiver/amplifier that allows use of two microphones (the handheld IRH-15c and neck-worn IRN-10). Also included are the external IRD-60 infrared sensor and ACS-6.5 in-ceiling speaker.
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