The performance of wireless microphones is often affected by various factors such as frequency interference and user's erroneous operation, and various failures occur. This article will introduce how to avoid and prevent the most common wireless microphone problems.

 

1.The system itself is not compatible

 

When using wireless microphones, there is always interference between the systems themselves. Although each system has its own frequency or interval of several megahertz, intermodulation distortion (IMD) can still cause mutual interference between microphones. If there is not enough megahertz space between the intermodulation signal and the operating frequency of the device, it is difficult for the receiver to pick up the signal from the transmitter. Typical phenomena are crosstalk between systems, frequent signal loss or excessive noise and distortion.

 

The minimum separation between frequencies depends on the design of the system receiver. Entry-level receivers may need to be 1 MHz from the nearest nearest system. The more expensive receivers usually have a narrower "window" of adjustment, allowing for smaller intermodulation frequency separations between each system.

 

Solution:

 

To avoid intermodulation distortion, select mutually compatible frequencies that have been calculated. For example, when only eight wireless microphones are used together, thousands of calculations are performed to ensure compatibility between the microphones.

 

2. The compatibility of the entire system is not enough

 

There are different degrees of compatibility between frequencies. If you know the system status, you can use more systems more boldly, but the key is how to weigh the compatibility of the entire system.

 

Most frequency-compatible software is designed with an important assumption that all receivers are always on or non-mute (even if some transmitters are occasionally turned off), so that all receivers will not pick up To intermodulation signals that may produce noise.

 

Solution:

 

To balance the maximum number of system devices with high performance, ensure that the level of compatibility between frequencies is appropriate for the system you are using. Keep the transmitter at least 10 feet away from the receiving antenna. If the RF output power of the transmitter is adjustable, use the lowest transmit power to cover the expected distance between the transmitter and receiver.

 

 

3.Interference from other signal sources such as TV stations

 

Wireless microphones are also subject to interference from other signal sources transmitting in the same spectrum. The most common is usually a television station. FCC rules require users of wireless microphones to avoid using the frequencies occupied by broadcasters in the same geographical area.

 

Solution:

 

Indoors, avoid interference on TV channels of 40-50 miles. When working outdoors, maintain normal use within a radius of 50-60 miles. Since the frequency of each city is different, the suitable frequency of the wireless microphone depends on the location. Equipment manufacturers often provide guidelines to inform users of different frequencies in different cities.

 

4. Interference from other digital equipment

 

Other wireless audio devices such as ear monitors, intercom systems, and non-wireless devices can also cause interference issues. If digital devices (CD players, computers, and digital audio processors) are installed close to wireless microphone receivers, they often emit strong RF noise and may cause interference. For transmitters, the most common sources of interference are GSM mobile phones and PDAs worn by moderators.

 

Solution:

 

When choosing a wireless microphone frequency, be aware of other wireless audio devices. Keep the digital device at least a few feet away from the wireless microphone receiver.

 

 

5.Selection and layout of receiving antenna

 

The receiving antenna of a wireless microphone is one of the biggest areas that is misunderstood. Antenna selection, layout, and wiring errors can cause short performance coverage areas and low signal strength, which can cause frequent dropped calls. The performance of modern diversity receivers is far superior to that of a single antenna type, but to optimize system performance and reliability, the antenna selection and layout must be correct.

 

Solution:

 

To ensure good diversity performance of the system, the antenna space must be at least one half-wavelength (about 9 inches 700MHz). The angle of the receiving antenna should be a "V" configuration, which can provide better signal pickup performance when the transmitter is moved or placed at different angles.

 

If the receiver is installed away from the performance area (such as in a device closet or enclosed rack), a half-wave antenna or directional antenna (preferably above the audience) should be installed remotely so that there is a clear Line of sight. Do not install ¼ shortwave antennas remotely because they use the receiver case as a ground antenna. If the antenna is installed far away from the stage, a directional antenna can be used to improve signal reception by picking up more signals in this direction and reducing other angle signal pickups. If a coaxial cable is used to connect the antenna to the receiver, an antenna amplifier may be needed to solve the problem of signal loss during cable transmission.

 

The amount of signal loss depends on the specific length of the cable and the cable type. Therefore, please calculate according to the manufacturer's recommendations. The total net loss of the signal should be controlled within 5dB.

 

 

6, artificial wireless signals are blocked

 

The human body may also interfere with wireless signals. The human body is mainly composed of a large amount of water and can absorb radio frequency energy. In addition, if the user puts his hand around the external antenna of the handheld transmitter, its effective output can be reduced by more than 50%. Similarly, if the flexible antenna on the transmitter is curled or folded, the signal will be affected.

 

Solution:

 

Keep the transmitter antenna fully extended and unobstructed to achieve the maximum range of signal transmission for optimal performance.

 

7, the voltage of the transmitter battery is not enough

 

The battery life of the transmitter is the number one concern for wireless microphones, and users are always trying to reduce the cost of the device with inexpensive batteries. Most wireless manufacturers specify alkaline batteries or disposable lithium batteries because their output voltage is relatively stable throughout the battery's life cycle. This is important because most transmitters experience distortions or loss of signal at low voltages. Rechargeable batteries often seem like the ideal solution, but most rechargeable batteries, even when fully charged, provide 20% less voltage than disposable batteries.

 

Solution:

 

In order to solve the battery problem, the voltage output requirements of the transmitter battery must be carefully compared at any time to ensure the sustainability of the battery throughout the work process. Lithium-ion and rechargeable alkaline batteries usually work continuously, while nickel-metal hydride and nickel-cadmium batteries may last only a few hours. This is especially true for 9-volt batteries, which perform similarly to disposable AA batteries.

 

8.Unadjustable launcher

 

Inherent noise and limited dynamic range of FM transmission make analog wireless audio transmission have its limitations. To overcome this, most wireless microphone systems usually use two audio processing methods to improve sound quality. Add pre-emphasis equipment to the transmitter and de-emphasis equipment to the receiver to improve the signal-to-noise ratio of the signal. The compressor and receiver expander in the transmitter can increase the dynamic range by more than 100dB. This makes the volume setting very important. If the audio level is too low, a chirping sound will be produced; if it is too high, it may cause distortion.

 

Solution:

 

For best sound quality, the input gain of the transmitter should be adjusted so that full modulation occurs at the highest volume without distortion.

 

 

9.The receiver output level is set incorrectly

 

With so much discussion of frequency, wavelength, and antenna, it's easy to overlook the most basic requirements of a wireless microphone system: To replace the connection cable between the signal source and the audio system, the receiver is usually equipped with output level control, Most wired microphones don't. This provides a better opportunity for more accurate matching from the receiver output to the input.

 

Solution:

 

Regardless of the microphone level or line level, the output level should be set to the highest practical level, while not exceeding the input limit of the audio system. This may be indicated on the input channel of the mixer, or it can be passed Judging by sound distortion.

 

10. Setting of wireless system

 

The most problematic aspect of wireless systems is that the waves themselves are constantly changing. Since the transition to digital television, the wave of analog and digital television channels has continued to change. The FCC is trying to figure out a way for consumer products (personal PDAs, smart phones or home devices) to use wireless TV channels for wireless Internet access.