May 7, 2013 4:05 PM, By Mark Johnson
By now, probably the majority of audio professionals are fully aware of the reallocation of available wireless frequencies in the UHF television spectrum by the FCC, and the ensuing relative upheaval to the wireless manufacturing community. To briefly recap: As of June 2010, frequencies in the UHF spectrum from 698MHz to 806MHz, otherwise known as the “700MHz band,” were ordered by the FCC to be made available for exclusive use by public safety agencies such as police, fire, and other emergency responders. Any other systems that operated in that band should have been removed from service and replaced with systems that would operate outside of that band. To further complicate the issue, the increased bandwidth required by the DTV stations just coming online exacerbated the situation by adding to the already crowded airwaves. The good news is the engineering and product development teams at many of the manufacturers have come up with nice options where wireless technology is concerned. Some incorporate digital technologies, and many new wireless offerings operate in the 2.4GHz range, 2.4GHz ISM band (or higher), far outside of the TV band. We’ll be looking at a variety of systems and implementations of wireless technology for production and presentation applications.
Featuring 24-bit/48kHz operation in the 2.4GHz ISM band, AKG’s DMS70 provides true, uncompressed audio transmission. Bidirectional communication between the transmitter and receiver allows for power off from the receiver for all connected transmitters, battery-status monitoring, and out-of-range warning. Available in 2- or 4-channel versions, the systems feature dynamic frequency selection and AES 128-bit encryption for secure operation. The DSR70 receiver features five XLR balanced outputs, one per channel, and one summed output for mixdown of the four channels. Approximate battery life for two AA Alkaline batteries is six hours, and seven hours for NiMH batteries. Operating range is 98.5ft. line of sight. Transmitter options include the DPT70 pocket transmitter and the DHT70 D5 and Perception handheld transmitters.
The Audio-Technica System 10 provides digital 24-bit/48kHz wireless operation in the 2.4GHz range. It is available in multiple system configurations, with handheld vocal microphone transmitters and UniPak bodypack transmitters for use with lavalier, headworn, and instrument microphones, as well as electric guitars. Up to eight channels can be used simultaneously. System 10 provides three levels of diversity: frequency diversity sends the signal on two dynamically allocated frequencies; time diversity sends the signal in multiple time slots; and space diversity uses two antennas on each transmitter and receiver. Automatic frequency selection finds clear frequencies each time the transmitter/receiver system is powered up. The System 10 ATW-R1100 receiver features balanced XLR and unbalanced 1/4in. output jacks with level control. The transmitters use two AA alkaline batteries with a typical battery life of seven hours.
The RAD360 from Audix is a UHF system operating between 614MHz and 662MHz, with 193 selectable frequencies (per system group or 24MHz spaced 125kHz apart) and dual-tuner, true diversity receivers. Transmitter battery life for either the T360 handheld or B360 bodypack transmitters is approximately 12 hours for two AA batteries. The handheld transmitter accepts capsules from the OM series dynamic microphones. The transmitter and receiver are synthesizer-controlled via Phase Locked Loop (PLL). Optionally, the AB-1 antenna booster can be used for increased range and improved signal to noise and the Antenna Distribution System allows up to four systems to be run off a pair of antennas. Rackmount kits for mounting one or two systems are available.
The Azden IR-CS or WS Infrared Classroom Systems are available as two complete systems (including speakers), or separate components are available for customization. The systems include an IRR-30P-powered dual-channel receiver, four ACS-6.5 in-ceiling or AWS-4.5 wall-mounted speakers, IRN-10 chest-worn microphone/transmitter, IRH-15c handheld transmitter, and IRD-60 ceiling-mounted sensor. The receiver provides two stereo aux inputs and up to three additional sensors may be added for larger installations. The handheld transmitter provides six hours of use with two AA batteries while the chest-worn transmitter provides up to eight hours.
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