Wider audio bandwidth
One quite beneficial aspect of this capability is audio bandwidth. The typical 24-bit/44kHz or 48kHz sampling rate can yield a virtually flat frequency response from 20Hz to 20+kHz, with any variation coming from the behavior of the particular mic capsule used with the transmitter. Also, companding circuitry with its potential to color the sound — a necessity with analog wireless — is no longer an issue. With digital wireless, high-definition sound joins HD video.
Digital transmissions require a lower signal-to-noise ratio to provide a useable signal. Several benefits arise from this characteristic. Range is usually greater in a digital wireless system for an equivalent RF signal strength from the transmitter.
A number of manufacturers offer variable-level transmitters, allowing the user to select an output sufficient to cover the distance without overly adding to RF congestion. Even the highest output levels are usually below the 50+mW typically used in analog transmitters — leading to a longer battery life of 10 or more hours.
Since the audio signal has been converted to numerical data before it is transmitted and meets error-correction algorithms within the receiver, it is much less prone to signal degradation that affects analog wireless mics. At the receiver output, audio is either excellent or gone. So, possible buzzes, hums, distortions and compromised audio bandwidth are no longer a factor. Greater interference resistance also leads to enhanced reliability, and signal encryption is widely available.
Finding open frequencies
The flexibility that analog frequency-agile wireless brought has been increased with new digital systems. A system that spanned 20MHz to 25MHz of UHF spectrum was the norm, yet new digital systems will operate over a much wider bandwidth. Some cover “only” 64MHz within a single receiver band, while others go beyond 150MHz. With such wide coverage, finding usable wireless channels, even in a crowded RF environment, is assured — without having to carry different bands of receivers and transmitters.
Frequency-agile systems usually have a scanning function that uses the receiver to run through its entire bandwidth and detect existing RF signals and clear spectrum. When the scan completes, it either offers or automatically sets a clear channel, which will then be synced wirelessly via an IR link or manually with the transmitter.
Typically, one frequency from a pre-coordinated group will be selected. Then, additional wireless mics can be set to the group’s other clear channels. In some systems, frequencies can be evenly spaced in open spectrum without interfering with one another.
Monitoring and control
Most professional digital (and analog) wireless receivers have the ability to be networked for monitoring and control. This control can stretch beyond the connected receiver, so frequency and other parameter changes can be made on transmitters without touching them. One new wireless system even has a bi-directional link,with the capability to put a transmitter that is on the talent into sleep mode to conserve battery life.
Some systems are even smart enough to monitor RF environments for problems, select backup frequencies and automatically switch a particular system to a clear channel. Supporting this networking software, both wireless mic manufacturers and third-party vendors provide powerful tools for RF analysis, site surveys and frequency coordination, including: spectrum analysis, visual depiction of your transmitters within the spectrum and alarms that notify of potential problems.