How To Choose Wireless Microphones
2. What makes wireless microphones different from each other?
TYPES OF WIRELESS MICROPHONES - Handheld Wireless Microphones vs. Handsfree Wireless Microphones
Handheld wireless microphones are literally held in the hand of a presenter or a vocalist. In this way the microphone can be used as a prop in a performance. Most importantly, the distance between the sound source (e.g. the mouth) and the microphone can be varied with a resultant change in volume and fidelity. This allows for a number of special effects in a performance to emphasize different phrasing. Think Frank Sinatra!
Here's an example of a top drawer vocal microphone from Shure.
Handsfree wireless microphones come in three popular configurations, or if you will sub-categories: lapel (or lavaliere) wireless microphones, collar wireless microphones and headband wireless microphones.
All three types of handsfree wireless microphones, as the name implies, leave the presenter with maximum freedom of movement. This is especially helpful for those who want to talk with their hands (e.g. sign language interpreters), operate multimedia equipment while they speak (i.e. using computers or projectors during presentations), operate heavy equipment (e.g. construction workers) or engage in self-defense or combat (self-explanatory). In addition, handsfree wireless microphones fix the distance between the sound source and the microphone which gives you a consistent volume level; this is especially useful when miking novice speakers in a public setting.
The Anchor Audio UHF 6400 is an example of a wireless microphone which has the option to be bundled with all three types of handsfree options (as well as a handheld wireless microphone).
TYPES OF WIRELESS MICROPHONES - VHF Transmitters vs. UHF Transmitters
All wireless microphones must overcome problems of transmission, especially when interference muddies or blocks a signal from the transmitter to the receiver. Transmission is affected by the wavelength of the signal and the type of antennae used in the receivers (receivers are discussed in the next section below).
VHF (Very High Frequency) radio signals in the range of 49MHz to 216MHz are the least expensive solution to wireless transmission. This is because in the VHF range your transmission works with a single antenna and does not require diversity antennae (discussed below).
The FCC divides VHF into a low band (49MHz to108MHz) and a high band (169MHz to 216MHz). Low band VHF is used by cordless telephones, walkie-talkies, radio controlled toys, television channels 2 through 6, and wireless assistive listening systems.
High band VHF is FCC approved for wireless microphone users. The first part of this high band spectrum, from 169MHz to 172MHz, includes eight specific frequencies, known as low band VHF. These are often referred to as "traveling frequencies" because broadcast television is excluded from them. The primary users of this band include businesses and government operations such as digital paging services, hydroelectric power stations, and the U.S. Coast Guard.
The downside of wireless microphones in this low band VHF range is radio frequency interference (RFI). Although broadcast television is excluded from the low band VHF range, the volume of traffic on these frequencies, and the spacing between them, makes using wireless microphones subject to interference. The interference problem becomes virtually intolerable when using three or more wireless microphones in this range.
The high band VHF range, 169MHz to 216MHz, is designated by the US government for broadcast and commercial film/video production. Within the high band VHF range audio transmission is significantly improved. Interference is less than that of low frequency radio waves. As a result, wireless microphones can be made with manageable antenna sizes that produce good results in almost any part of the US.
The Ultra High Frequency (UHF) range contains several bands portions of the electromagnetic spectrum from 470MHz to 806MHz that have been set aside by US government for wireless microphone systems.
The shorter wavelength of the UHF radio waves creates higher energy transmissions that punch through interference. Greater bandwidth is allowed for UHF signals (eight times more than the High Band VHF), permitting a larger number of available frequencies without compromising the intervals between frequencies. This allows more systems to operate simultaneously - a significant benefit in complex setups and concert applications. By the way, you can also run both UHF and VHF systems in the same location without mutual interference.
A drawback of the shorter UHF wavelength in wireless microphones is a reduced range for a UHF signal compared to a VHF signal. In addition, UHF transmitters work better when there is a "line-of-sight" between transmitter and receiver operation. Both of these limitations have to do with the way that the shorter wavelengths of the UHF band reflect from small metal objects and move around obstacles such as corners or intervening barriers. The susceptibility of UHF transmitters to interference and dropouts is best addressed by diversity receivers discussed below.
Historically when High Band VHF transmitters were the dominant type of wireless system, a relatively simple single antenna was sufficient. But with the greater capability of UHF transmitters a better antenna was needed to take advantage of the greater potential of the system. Thus the birth of the diversity receiver.
A true diversity system goes one step further by using two separate receivers housed in a single unit each of which is paired with one of the antennae. Whichever receiver detects the stronger signal is the one that is used.
TYPES OF MICROPHONES - Radio Frequency vs. Infrared Transmission
For a discussion of Radio Frequency (RF) vs. InfraRed (IR) transmitters see our separate article.
Although they are based on different technologies (lightwave vs. radiowave) infrared wireless microphones and UHF/VHF
wireless microphones share many similarities. Here are some useful tips:
Is UHF always the better choice compared to VHF transmitters? Not necessarily. Your needs and your budget are the deciding factors.
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