Wireless Management
Some manufacturers have developed a systems approach to their higher end wireless offerings, including networking via Ethernet, real-time detection and communication of transmitter and receiver parameters, remote control of the wireless equipment, system setup and modifications, and even monitoring and on-the-fly changes on a computer screen.
Supplementing the basic transmitters and receivers, other devices manage the interconnection and communications among all the system components and oversee the RF environment and frequency allocations moment by moment.
For example, the new Axient system from Shure provides continual wide-band RF monitoring and calculates/deploys a set of compatible frequencies plus backup frequencies, while taking into account any new interfering signals.
These frequencies are passed to the receivers and transmitters, which are capable of seamlessly and simultaneously switching channels if necessary in response to interference.
The handheld can be set to transmit on two channels at once, with the 2-channel receiver assigned to both of those channels and “blending” the results (and if needed changing both Rx and Tx to a clear backup channel).
The combined effect is seamless audio transmission without glitches or dropouts. Enough redundancy and intelligence is built into this system that it will continue to function even if the network goes down.
Wide-Spectrum Receivers
A very useful feature of the newer venue/ touring class wireless systems is that the receivers cover a very wide bandwidth, so that they can be used anywhere without having to predetermine which frequency “splits” to travel with.
Just a few years ago, a frequency-agile system might cover a bit over four UHF television channels – about 26 MHz. Shure Axient covers the entire 228 MHz spectrum between 470 to 698 MHz, while the AKG DMS 700 has a 155 MHz tuning range. It gives the potential of many channels of wireless being used without interference in the same venue, even in a crowded RF environment.
Scanning & Syncing
Virtually all of the new wireless systems, whether digital or analog, have powerful algorithms to scan the relevant RF band for interfering signals, perform intermod calculations, and return a set of “good” frequencies for the present location.
A few even display the spectrum graphically. Many offer pre-determined groups of channels which are mutually compatible and fit into the existing radio environment of wireless mics, devices, and television sources.
Once these channels are determined, the transmitters can be synced with the receivers, often using a close-range infrared link; a spare transmitter can be substituted rapidly using the syncing technique.
Audio-Technica SpectraPulse: 14 channels in 2 rack spaces; no frequency coordination required; 500 MHz bandwidth; 6.35 GHz center frequency; 16-bit AD/DA; 24 kHz sampling rate; 3 ms sync/re-acquisition time; 75-foot range; AES level 3, 128-bit encryption; contact closure input/output (on Audio Control Interface) provides control interface with external devices.
Some of the higher end systems sync using digital transmissions on the carrier frequency. Communication between the transmitter and the receiver also can send battery status and other information to the receiver (or a monitoring computer).
These new systems make setup much easier than before, though it’s always a good idea to double-check the settings and also to walk the coverage area.
Security & Encryption
For some wireless applications, audio quality and reliability is not enough. The proceedings are so sensitive that no information traveling on those channels can be allowed to be detected and/or decoded.
Several wireless microphone systems have been designed with various levels of encryption so that even if the signals are captured, no usable information can be extracted from the data stream.
With some of the 128-bit encryption schemes, only the designated receiver that has been immediately synced with the transmitter is able to return the signal to audio. Even the engineers who designed the system, another receiver of the same type and brand, or a super-computer can unscramble it.
As digital technology meets wireless, the ideal of wired reliability and sound quality is coming closer to reality.
These innovations in digital wireless, and others still on the drawing board, will help ensure that the benefits of wireless will more and more outweigh any disadvantages.
Author’s Note: Thanks to Erik Vaveris of Shure, Karl Winkler of Lectrosonics, and Don Boomer of Line 6 for their time and input for this article.
Gary Parks has previously served as wireless product manager for Clear- Com and has also worked with wireless product management at Electro-Voice. He is currently with EDX Wireless and is a freelance writer.