A wireless microphone
wireless microphone or wireless microphone, audio equipment of the transmission of sound signals, composed of two parts of the transmitter and receiver, often referred to as a wireless microphone system.
Transmitter battery-powered sound, the microphone is converted to audio signals, after the handling of internal circuit, will contain the audio information of the radio wave launched into the space around the receiver general municipal electricity supply received by the receiving antenna to the radio transmitter sends wave, after the processing of the internal circuit, to extract the audio signal and output signal line to the PA system, complete the wireless transmission of audio signals. a receiver usually consists of a set, 2 sets or 4 sets of receiver circuit ,cheap nike shoes, respectively, to receive a 2 or 4 wireless microphone signals, were referred to as two most common models on the nature of the wireless microphone is a one-way wireless communication system.
1.1 UHF band
wireless microphone system is a sound signal by radio transmission equipment, wireless microphone and receiver to send and receive high and low frequency, can be divided into different frequency bands commonly used FM, VHF, UHF, several bands of the FM band refers to the public FM radio with 88 ~ 108MHz frequency band near the band, usually only some simple wireless microphone the mining acenaphthene the band to the VHF band, divided in accordance with international standards is 30 to 300MHz frequency band, the FM band of the above-mentioned fact, included in the VHF band, but by Ju close to the public FM radio (referred to as FM) band, so called the UHF band to the FM band to the VHF band wireless microphone is much more expensive than Acenaphthene 170 ~ 260MHz band, often referred to as the VHF high band (VHF HIGH BAND)., refers to the 300 ~ 3000 MHz band, wireless microphones generally adopted acenaphthene 400 ~ 830MHz frequency band, more than 830MHz band less mining acenaphthene, Ju 830 ~ 960MHz band GSM and CDMA mobile phone interference, diffraction ability of more than 960MHz band becomes worse, so the most popular UHF band 800MHz band (740 ~ 830MHz)
several terms terms to understand the performance characteristics of the wireless microphone, it is necessary to first understand the specific meaning of the basic terminology and key performance indicators of the wireless microphone wireless microphone in addition to the same wired microphone audio indicators, but also unique terminology, and performance indicators, the following one by one introduced.
, Squelch: wireless microphone receiver did not receive the signal or the signal is weak, in order to avoid the output noise will be automatically cut off the output signal, which feature is called mute (Squelch) If there is no mute function, or adverse squelch function when no signal or weak signal, the speaker cone will emit noise noise will affect the sound quality, destruction of the atmosphere, and even damage amplification devices.
dead: also known as the dead zone or blind spot. wireless microphone during the move, the receiver receives the signal due to distance and the relative position of the different obstacles blocking changes in the strength of certain locations in the normal use of distance, too weak signal makes the receiver squelch circuit action, cut off the output signal; after leaving that position, but also the normal reception and output. the location known as the dead points or blind spots. wireless microphone close to or exceed the effective distance, inevitably there will be dead, if the circuit design is reasonable, is dead, just no sound; if poor design or manufacturing, not only did not sound normal , but the noise.
diversity reception: refers to the wireless microphone receiver, respectively, from the two antennas to receive signal with a wireless microphone, choose to use a strong signal all the way through the internal circuit in this way can greatly eliminate the receiver dead zone, to avoid the noise of the mute or dead. diversity reception there are two ways: antenna diversity and put diversity in the way of antenna diversity, there are two receiving antennas, a control circuit and a receiver circuit, reception is weak in the work, the control circuit will automatically switch to a new antenna. put in in the way of diversity, in addition to the two antennas and a control circuit, there are two complete receiver circuit simultaneously. track switch by the control circuit to output a better way audio signals. by Ju at any time to track a strong signal, thus the effect is better than the former, but the circuit complexity and high cost of this diversity in a manner often called dual tuner, true diversity. general in live performances, studio and other important occasions, we must use a dual tuner true diversity of products, to ensure that in the practical operating distance is not a dead point.
multi-channel: wireless microphone, the carrier frequency is fixed, the user can not be changed in the course of Ju wireless microphone signals via radio waves to transmit voice, so when the work environment with the same carrier frequency or close to external signals occurs interference, so that the receiver of the receiver distance decreases, the output noise, and even receive less than the microphone signal. this situation, the manufacturer has developed a multi-channel wireless microphone system. transmitter (wireless microphone) and receiver operating frequency is adjustable, so users can change the carrier frequency of the system in the face of external frequency interference, to avoid the interference signal and normal work; In addition, if using multiple wireless microphone at the same venue, you can also facilitate the adjustment of each microphone in a different frequency without disturbing each other, coordination and most of the large-scale professional theatrical use of wireless microphone is a multi-channel system, 8-channel 16-channel, or even more channels, which The most common is 16 channel multi-channel system is generally adopted acenaphthene phase-locked loop (PLL) frequency synthesizer technology, microcomputer control technology and other related technologies and production of technical requirements, equipment requirements, production costs and product performance are far higher than ordinary models. some products currently on the market, is a fixed frequency of the first products of the same model can be produced into different frequency products, the user can choose the time of purchase, but after the purchase, not use adjust its operating frequency, and some manufacturers this case the nominal as requiring special attention, there are several ways can be distinguished: First, observe whether there is a switch or button to adjust the channel on the receiver panel; see its promotional materials or instructions whether marked with adjustable frequency Road tone letter audio signal and noise signal ratio, expressed in decibels (dB). The larger the value, the signal is purer, the better the machine performance.
receiver sensitivity: the radio or walkie-talkie, the receiver sensitivity is when the receiver machine output provides signal when the signal to noise ratio, the required minimum size of the RF signal input. the smaller the value, indicating that the higher the receiver sensitivity of the receiver in the wireless microphone is critical receiver squelch value of the input RF signal, said signal. Ju is not output when the input signal is lower than the mute point, the receiver is muted, for example,Nike Air Max LTD, the receiver sensitivity of a product labeled as input signal is lower than-90dBm (ie, 7mV), the receiver will enter the squelch state, such a label accurately reflects the receiver to receive some products, the sensitivity of the indicators adopted acenaphthene similar radios, walkie-talkie marked, for example, labeled indicator is much higher than 12dB, so this labeling method does not correctly express the receiving ability of the receiver.
RF output power: the wireless microphone transmitter the size of the signal energy to the space launch, usually milliwatts (mW) said, usually between 5 to 50 mW.
effective working distance: refers to the parameters marked in the wireless microphone can be the maximum distance of the normal transmission of signals. products in general,nike air max, the majority specified in the open or ideal conditions. Ju actual transmission distance of wireless microphones, subject to the actual environmental impact can not be accurately marked. indicators in the open ground or ideal conditions, can provide a reference, and can be compared with each other. In fact, to measure the transmission capacity of the wireless microphone, depending on squelch when the transmit power and critical reception sensitivity of these two indicators are translated into the same unit, the difference is the greater,nike shox, effective work under the same environment the greater the distance, combined with receiver diversity type, and which species diversity the way, you can more clearly estimate the effective transmission distance than the pair of different products. In general, the sub-set receiver distance is more than presumptuous diversity receiver, put the diversity receiver is greater than the antenna manufacturers a few of diversity receiver
market products. UHF band wireless microphones popular products currently on the market, the domestic production of such products are developed in recent years, its own development and production capacity , but the market brand, most of which is listed on the OEM basis. in the UHF band wireless microphone products can be divided into the different types of pocket fertile, the following one by one brief segment products of all kinds of U prepare constitute the water chestnut performance characteristics.
the 3.1 multiplier U-microphone of the multiplier-type products in the VHF band products based on the use of the multiplier circuit, will transmit and receive frequency to 2 to 4 times, the work frequency into the UHF band, product upgrade along with the production of these products easier, costs have increased marginally improved sound; but from Ju increase the multiplier, the total efficiency of the transmitter circuit has declined, likely to lead to power consumption too fast or reduce the operating distance, and such products, spurious emissions, anti-interference ability is not strong, its operating frequency is user can not change the types of products currently on the market mainly in the 550MHz band and 750MHz band. the type of product is U segment of entry-level products.
3.2 multiplier points set multiplier points set on the basis of the above multiplier to increase the antenna diversity circuit, constitutes an octave sub-set of products. technically can also be designed to put the sub-set of products, but in view of the overall grade of such products are generally not designed so that.
text from the US-core blog