I. Overview

 

Due to the advancement of today's radio communication technology, the quality and functions of wireless microphone products have been relatively improved, reaching mature and practical fields: while the number of manufacturers is increasing, and the price is decreasing due to competition, triggering consumers' gradual love of this product And universal application. The author has eight years of experience in selling and manufacturing professional wireless microphones. Here, I provide the latest technical points on the design of this product, so that consumers can judge how to choose a value-for-money before purchasing this product. Excellent products, but also provide manufacturers' reference to explore how to produce and sell advanced products that satisfy consumers.

 

Understanding the types of wireless microphones

 

Before choosing a product, you should first have a basic concept of the product category to choose a model that suits your needs. The types of wireless microphones can be divided into many different types according to different definitions.

 

1. Distinguish according to the frequency of transmission:

 

QA, FM wireless microphone: commonly known as FM means FM

 

88-108MHz international FM broadcasting band. Early consumer wireless microphones used FM radio to receive. The system was simple and low cost. However, due to the use effect, it can meet the requirements of professional quality. At present, it can only be a toy for children or students.

 

B, VHF wireless microphone: It is divided into two types of low frequency and high frequency band. The former uses the VHF50MHz frequency band. Because the frequency is low, the antenna length is too long, and it is most vulnerable to interference from various electrical clutter. Products have now been replaced by high frequency bands and are gradually disappearing from the market. The latter uses the VHF200MHz frequency band. Due to the higher frequency, the antenna is shorter, and it can even be designed as a hidden antenna. It is convenient, safe and beautiful, and the clutter interference of electrical appliances is greatly reduced. Cheap, so it has become a popular model on the market today.

 

2. Differentiated according to the receiving mode:

 

A. True diversity receiving wireless system: Due to the physical phenomenon of "dead-point" in radio waves, the receiver's sound output has the disadvantage of intermittent or instability. To resolve this shortcoming, professional models must be improved by using the "Automatic switching diversity receiving" method of dual antennas and dual tuners.

 

B. Non-diversity receiving wireless system: Due to the complicated and precise circuit design of the above models, the assembly is difficult and the cost is high. Generally, the low-priced models do not use the automatic selection design. Therefore, it is impossible to eliminate the disadvantage that the wireless microphone generates sound interruption in use. Of course, this model cannot meet the basic requirements for professional use.

 

3. Distinguish according to oscillation mode:

 

A, Qualtz locked models: Quartz oscillators are used to generate fixed and accurate fixed frequencies for transmission and reception. The circuit is simple and the cost is low. It is the standard circuit design of today's wireless microphones. This type of microphone and receiver is fixed for a single frequency pairing and cannot be changed or adjusted.

 

B. Phase-locked frequency synthesis (PLL Synthesized) models: In order to avoid the use of wireless microphones in the event of interference with other signals, or to use multiple microphones at the same time, you need to change the channel conveniently and quickly at any time, so The circuit design of PLL is adopted to meet the requirements of this function.

 

4. Differentiated by the number of receiver channels:

 

A. Single-channel models: A non-automatic or automatic selection receiver with only one channel is installed in the chassis of a receiver. The former has almost no market in Taiwan. Big color goods). The latter is easy to use and has stable characteristics. It is suitable for professional occasions to use multiple channels at the same time to avoid signal interference.

 

B, dual-channel models: In a receiver chassis, two channels of non-automatic or automatic selection receivers are equipped to make full use of the space of the chassis and reduce costs. The former is the so-called "Asian fighter" model, because of its simple design, it has become the main model of Taiwan's mass-produced low-cost manufacturers. The latter because of the complicated mechanism and circuit, it is not easy to deal with internal interference and antenna mixing and matching. Only a few manufacturers have professional models.

 

QC, multi-channel models: In a receiver chassis, receivers equipped with more than four channels are mostly designed with modular receiving modules. Mainly applicable to the use of professional rack mount models.

 

The choice between price and quality

 

Recently, the quality of wireless microphones made in Taiwan has improved significantly due to the increase in consumer requirements: the price has fallen sharply due to fierce competition from manufacturers. Therefore, in order to win orders, some smaller manufacturers are not committed to research and development of more advanced models, but to produce simpler models with lower prices to attract consumers. As the saying goes: "One cent, one cent". Consumers often buy products of poor quality because they are greedy for a little cheaper prices. Some consumers may be misled by excessively superstitious brand names or by false advertising by manufacturers. So the money is not worth the fare. How to choose a good value-for-money model, you should first respond to the quality positioning required by yourself, and further understand how to evaluate the principles of the quality of wireless microphones in order to choose a truly satisfactory product.

 

Fourth, the technical background of the manufacturer determines the quality of the product

 

Wireless microphone products are products designed by combining audio and wireless communication technologies. They are completely different from the technology and equipment for manufacturing wired microphones. Therefore, wired microphone manufacturers who also manufacture "microphones" may not be able to manufacture wireless microphones and wireless communication products. Manufacturers may not be able to make good wireless microphones. Only manufacturers with a long-term background in professional audio technology and wireless high-frequency technology can make excellent wireless microphones. A few years ago, the famous SHURE company that made wired microphones often advertised that its wireless microphone could be as good as its wired microphone SM-58, which is a misleading advertisement! The biggest difference between wireless microphone products and other wired products is that the use effect is very closely affected by environmental conditions. Therefore, a high-quality wireless microphone cannot be designed in the laboratory in a short period of time. It also requires long-term use. After the actual use in various environments, the designer will return the gains and losses to the design engineer, and then continue to improve without research and development to produce a truly perfect product. Therefore, to choose a good wireless microphone product, we must choose a person with professional technical background and long-term manufacturing experience.

 

V. An excellent wireless microphone should have the following excellent characteristics:

 

1. The appearance has a design that conforms to ergonomics and aesthetics: The body of a handheld wireless microphone must have a size and beautiful shape suitable for hand control. Generally, the traditional tube is a bamboo tube or trapezoid, which is not only aesthetic, It is also not suitable for grasping by hand, especially for users who are prone to sweat, and it is not easy to grip and slip. The most suitable shape for holding is the double inner curve shape with a smaller middle diameter than the two ends, like a Chinese Guanyin bottle or a woman's waist. It is not only beautiful in shape but also easy to grip.

 

2. The handheld microphone should use advanced hidden antenna design: the biggest difference between humans and monkeys is that there is no tail. Early wireless microphones had an external antenna at the end. Advanced wireless microphones overcome technical difficulties. Instead of using outdated external designs, the most perfect hidden antenna design makes wireless microphones easy to use. The advantages of safety, beauty and no breakage.

 

3. Assemble a good sound head: the quality of the sound head determines the first level of the sound quality of the wireless microphone. There are two types of sound heads: dynamic coil type and capacitive type. The dynamic coil type uses a coil loaded on a diaphragm to convert sound energy into electrical energy signals between high-density magnetic fields. There is a limit to the voice coil characteristics of this voice head. But the basic structure is simple and the price is cheap. It is the most popular model on the market. Condenser microphone is a high-level microphone combined with electronics and structure. Its pronunciation is to use the change of inter-electrode capacitance to directly convert sound into electrical signal with ultra-thin gold-plated vibration film. The most important feature of advanced condenser microphones is that they can display extremely clear original sound quality. The high and low frequency response is very broad and flat. The sensitivity is very high. The directivity and dynamic range are large. Used in professional equipment such as recording studios, professional stages, and test equipment. The only disadvantage is the need to provide bias (Phantom Power), but because the wireless microphone itself has a power supply, the condenser microphone is the best match for the wireless microphone, so that all the advantages are fully exerted on the wireless microphone. At present, Taiwan MIPRO wireless microphones are the only products equipped with advanced condenser capsules.

 

4. The microphone must have the superior characteristics of low touch noise: the hand-held wireless microphone produces frictional touch noise between the palm and the palm, which affects the normal sound quality, especially the wireless microphone itself has a sensitive preamplifier, which makes this kind of Touch noise performance is more serious and becomes a technical bottleneck. In general, wireless microphones have no professional design experience, and in order to reduce manufacturing costs, they use crude circuits, use cheap microphones, poor suspension design, and cheap tube surface treatments. Therefore, the sound quality is unclear and cannot be overcome by the microphone. Touching the noise will degrade the original sound, so when choosing a wireless microphone with good quality, you must pay special attention to selecting features with extremely clear sound quality and ultra-low touch noise.

 

5. It has the function of eliminating the interruption or instability of the sound: the signal transmitted by the wireless microphone is attracted and reflected by the surrounding environment, which causes the phenomenon of the dead angle of the signal received by the receiving antenna, causing the shortcomings of the interrupted or unstable output sound. This phenomenon is not allowed to occur especially in professional occasions. In order to solve this shortcoming, only by adopting the most advanced automatic selection receiving system can the most perfect effect be obtained. Generally, the popular cheap dual-channel receivers on the market do not have this automatic selection and reception function, and the above disadvantages cannot be avoided, so they can only be used in short-range home karaoke occasions. In professional places or users who value the sound quality, they must choose the model of the automatic selection and reception system to meet the sound quality requirements and obtain a perfect performance.

 

6. It has the function of preventing noise and loud noise caused by interference during standby: most receivers have a mute control function (Squelch Control). When the power is turned on without a microphone signal input or the signal strength is lower than a certain signal-to-noise ratio, the mute The control circuit will turn off the output circuit, and the main receiver is completely muted to prevent noise output. When the microphone signal is turned on, the receiver immediately activates the mute circuit to allow the audio circuit to output the sound of the microphone. However, when the microphone power is turned on and off, or when the microphone signal is turned off, occasionally encountered signal interference beyond the intensity of the mute control, the receiver mute circuit will also start to output loud noises due to these impact noises and interference noises. In order to solve this deficiency, the so-called "sound lock mute circuit" is installed in advanced models to suppress it. The principle is to add a fixed super audio modulation signal to the microphone's transmission signal: a discriminator is also installed inside the receiver, so the receiver must receive a microphone signal containing this fixed super audio modulation signal When this happens, the output circuit can be activated to achieve the function of preventing other signals or noise interference. In order to protect your valuable audio system from being damaged by loud noises, you must choose a model with a code lock and mute function.

 

7. Multi-channel non-interference function: the biggest technical bottleneck of using wireless microphones is the problem of signal interference, especially the more the frequency is used, the more serious the interference problem, so the situation of using multiple wireless microphones at the same location at the same time In order to avoid interference, in addition to carefully selecting frequencies that do not interfere with each other and avoiding adjacent external signal interference, the receiver must have excellent selectivity, and the radiated harmonics of the transmission and reception must be filtered to be very clean. In order to avoid mutual interference of signals. Generally, the receiver in the VHF band can be used for 12 frequencies at the same time, and the MIPRO products in Taiwan can use 24 frequencies at the same time without interference, even under specific conditions, specially designed And arrangements can reach more frequencies at the same time.

 

8. To solve the simultaneous use of multiple channels and avoid interference, multi-channel series models that can be digitally locked to change the frequency should be selected: The traditional wireless microphone system is designed to use quartz to lock the fixed frequency. This model is used in situations where multiple channels are used Or in the case of strong signal interference, the desired frequency cannot be replaced arbitrarily, but the entire unit must be replaced. In order to solve this deficiency, advanced models use the phase-locked frequency synthesis (PLL Synthesized) method. Dozens of frequencies pre-stored in the transmitter and receiver can be changed by the user at will, although this advanced design has a higher cost. , But it provides very convenient functions for distribution and users to completely resolve the above-mentioned shortcomings. Taiwan has already produced a complete series of products with the most advanced design and the most reasonable price.

 

9. To avoid frequency "traffic jams" or signal interference, products with digitally locked UHF channel systems should be selected: due to the current use of wireless microphones in the VHF200MHz frequency band, the problems of signal interference and various electrical noise interference are becoming more and more serious. Therefore, the frequency of professional-grade wireless microphones has been gradually increased to 800MHz UHF band recently, and the PLL phase lock circuit is used. The preset multi-channel design can be arbitrarily switched to avoid interference from other signals and general electrical noise. . Because the circuit design of the UHF band is more complicated and the high-frequency parts used are more precise, the current price is still relatively high, and there are fewer manufacturers in mass production. However, UHF models are the best choice for professional quality and have gradually become the future. Popular trend. Taiwan still produces a full range of advanced models and complete peripheral equipment with MIPRO.

 

10. Products with international quality certification and passing telecommunication regulations: Excellent wireless microphone products must be manufactured by factories that have passed international quality certification, and must also be certified by radio regulations in various countries before they can be legally sold and used. Consumers should choose to use certified products to ensure quality.

 

Collection and evaluation of software:

 

The most basic software source for purchasing products is catalogues provided by manufacturers and advertisements for magazines. However, generally small-scale manufacturers with incomplete equipment cannot provide correct values ​​at all, making consumers unable to understand the analysis and comparison from the catalogue. Some manufacturers even use catalogs and advertisements to make exaggerated facts and mislead consumers. But quality is not made out of the mouth, but made. Smart consumers today have developed information, as long as the actual products of the manufacturers are analyzed, tested and compared to get the correct quality evaluation.