Related technical terms of wireless microphone
1. Squelch
When the receiver of the wireless microphone does not receive a signal, or the signal is weak, in order to avoid output noise, it will automatically cut off the output signal, this function is called squelch. If there is no squelch function, or if the squelch function is poor, noise will be emitted from the speaker speakers. Noise will affect the sound quality, destroy the atmosphere of the scene, and even damage the amplifier equipment.
2. Dead point
Also called dead zone. During the movement of the wireless microphone, the signal received by the receiver will vary in strength due to differences in distance, relative position, or obstructions. In some positions within the normal use distance, the too weak signal will make the squelch circuit in the receiver act and cut off the output signal; after leaving the position, it can receive and output normally. This position is called the dead center or dead zone.
3. Diversity reception
It means that the wireless microphone receiver can receive the signal of the same wireless microphone from two antennas, and select the stronger one through the internal circuit. This method can greatly eliminate the receiving dead zone and avoid mute or dead spot noise. There are two ways to receive diversity: antenna diversity and mid-range diversity.
In the antenna diversity mode, there are two receiving antennas, a set of control circuits and a set of receiving circuits. When the received signal is weak during operation, the control circuit will automatically switch to use another antenna.
In the medium amplifier diversity mode, in addition to two antennas and a set of control circuits, there are two complete sets of receiving circuits, which work at the same time, and are tracked and switched by the control circuit to output a better audio signal. Since this method tracks strong signals at any time, the effect is better than the previous method, but the circuit is complicated and the cost is high. This diversity method is often referred to as double tuning, true diversity, and so on.
4. Multi-channel
In general wireless microphones, the carrier frequency is fixed, and the user cannot change it during use. Since the wireless microphone transmits sound signals through radio waves, when there is an external signal with the same or close to its carrier frequency in the working environment, interference will occur, reducing the receiving distance of the receiver, outputting noise, or even failing to receive microphone signal.
5. Signal-to-noise ratio
Refers to the ratio of the original audio signal to the noise signal in the output signal when the receiver receives a signal of a specified strength (usually 60dBμV), expressed in decibels (dB). The larger the value, the purer the signal and the better the machine performance.
6. Receiving Sensitivity
In a radio or walkie-talkie, the receiving sensitivity refers to the size of the minimum RF signal that needs to be input when the receiver outputs a signal with a specified signal-to-noise ratio. The smaller the value, the higher the receiving sensitivity of the receiver. In wireless microphones, it should be represented by the value of the input RF signal when the receiver is critically squelched, because when the input signal is lower than the squelch point and the receiver is in the squelch state, no signal is output.
7. RF output power
Refers to the size of the signal energy that the wireless microphone transmitter transmits to the space, usually expressed in milliwatts (mW), generally between 5 and 50 mW.
8. Effective working distance
Refers to the maximum distance that the wireless microphone can transmit signals normally. Most of the parameters indicated on general products are in open fields or ideal conditions. Because the actual transmission distance of the wireless microphone is affected by the actual environment, it cannot be accurately marked. Only indicators in open field or ideal conditions can provide reference and can be compared with each other.
In fact, to measure the transmission capability of a wireless microphone, it depends on the transmit power and the reception sensitivity at critical squelch. After these two indicators are converted into the same unit, the greater the difference, the longer the effective working distance in the same environment. Combined with whether the receiver is a diversity type, and which diversity method it is, the effective transmission distance of different products can be clearly estimated and compared. Generally speaking, the effective distance of the diversity receiver is larger than that of the non-diversity receiver, and the receiver of the medium amplifier diversity is larger than the receiver of the antenna diversity.
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