How to Solve the Problems of Wireless Microphone?

- Sep 10, 2018-

1. There is always a problem of interference between the systems themselves when using a wireless microphone. Although each system has a frequency or interval of several megahertz, intermodulation distortion (IMD) still causes mutual interference between the 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.

Solution: To avoid intermodulation distortion, select the calculated compatible frequencies. This requires a wealth of transmitter and receiver design knowledge that wireless system manufacturers often have calculated for these frequencies. For example, when only 8 wireless microphones are used together, thousands of calculations are performed to ensure compatibility between the microphones. Digital can only be assigned by frequency, preset 48 UHF optional channels, effectively avoiding signal interference

2. Wireless microphone is compatible, but not enough

There is a different degree of compatibility between the frequencies. If you know the system well, you can use more systems more boldly, but the key is how to balance the compatibility of the whole system.

Most frequency-compatible software has an important assumption in design that all receivers are always on or off (even if some transmitters are occasionally turned off), ensuring that all receivers are not picked up. To the intermodulation signal that may produce noise.

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

3. The wireless microphone is also subject to interference from other sources transmitting from the same spectrum. The most common is usually a TV station.

Solution: Indoors, avoid interference on 40-50 mile TV channels. When working outdoors, keep it within 50-60 mile radius. Since the frequency of each city is different, the suitable frequency of the wireless microphone is determined by the location.

4. Other wireless audio devices such as ear monitors, intercom systems, and non-wireless devices can also cause interference problems. Digital devices (CD players, computers, and digital audio processors) often emit strong RF noise and can cause interference if installed close to the wireless microphone receiver.

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

5. Receiving antenna

The receiving antenna of a wireless microphone is one of the most misunderstood areas. Errors in antenna selection, layout, and routing can result in short distances in the performance coverage area and low signal strength, resulting in frequent dropped calls. The performance of modern diversity receivers is far superior to the performance of individual antenna types, but to optimize system performance and reliability, antenna selection and layout must be correct.

Solution: To ensure good diversity of the system, the antenna space is guaranteed at least one and a half wavelength (about 9 inches 700MHz).

6. Unintentional signals are blocked

The human body may also interfere with wireless signals. The human body is mainly composed of a large amount of water, which can absorb radio frequency energy. In addition, if the user surrounds the hand-held transmitter external antenna, 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 also be affected.

Solution: Keep the transmitter antenna fully deployed and unobstructed for maximum signal transmission for optimal performance.

7. The voltage is not enough

The battery life of the transmitter is a primary concern for wireless microphones, and users are always trying to reduce the cost of the equipment through inexpensive batteries. Rechargeable batteries often seem to be the ideal solution, but most rechargeable batteries provide a voltage that is 20% lower than the disposable battery voltage, even when fully charged.

8. Non-adjustable transmitter

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

Solution: For the best sound quality, the transmitter's input gain should be adjusted so that the full modulation occurs at the highest volume, but without distortion.

9. Receiver output level setting error

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

Solution: Regardless of the microphone level or the line level, the output level should be set to the highest level that is practical and does not exceed the limit of the input of the audio system. This may be indicated on the input channel of the mixer. It can also be judged by listening to the distortion of the sound.

10. Wireless microphone settings

The most troublesome problem with wireless systems is that the waves themselves are constantly changing. Since the beginning of digital TV conversion, the analog and digital TV channel radio waves have been constantly changing.

Solution: It used to be easy to know if the VHF band TV channel in the city where the user is located is odd or even. However, when people install and use wireless microphones (as well as in-ear monitors and intercom systems, etc.), they must periodically check the local spectrum status even when working on a site they are familiar with.



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