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There are wireless microphone frequency bands that are acceptable and some that are prohibited.
Microphones and other devices that have wireless microphone frequency bands within a specific range may have to be replaced or have their frequency settings changed.
But before we look into that, let’s see what a microphone is.
A microphone is a hardware device and a very important component in electronic devices such as hearing aids, voice recorders, radio broadcasting, and other communication tools.
Basically, the electrical signal generated by the microphone is very low, therefore a signal amplifier is needed which is usually called an amplifier.
If you look at the basic way it works, a microphone captures sound waves and converts them into analog signal electrical vibrations to be further amplified and processed as needed.
Table of Contents
- What Wireless Microphone Frequency Bands Are Legal?
- Characteristics and Types of Microphones
- Types of Microphone Based on Their Uses
- How Does Wireless Microphone Work?
- Wireless Microphone Frequency Bands
- Regulation of Wireless Microphone Frequency Bands
- Final Thoughts
What Wireless Microphone Frequency Bands Are Legal?
It should be noted that each type of microphone has a different way of converting its energy form, but they all have something in common, the diaphragm.
Let’s get right into it and see which wireless microphone frequency bands are legal.
Characteristics and Types of Microphones
There are 10 common types of microphones in the industry, you don’t really have to know what the mechanics and science behind each type is.
You only need a basic understanding of how they are unique and which one is best used in different situations.
Liquid microphones, invented by Alexander Graham Bell and Thomas Watson, were among the first microphones worked on being developed, and they were the pioneers for what would later become condenser microphones.
Early liquid microphones used metal cups filled with water and sulfuric acid.
The diaphragm is placed over the cup with a needle on the receiving side of the diaphragm.
The sound waves will cause the needles to move in the water.
A small electric current runs to the needle, which is modulated by sound vibrations.
Liquid microphones are not functional devices, but they are a great scientific experiment.
The oldest and simplest microphones use carbon dust.
This is the technology used in the first telephones and is still used in some phones today.
Carbon dust has a thin metal or plastic diaphragm on one side.
Once the sound waves hit the diaphragm, they squeeze the carbon dust, which changes the resistance.
By running a current through the carbon, the resistance causes a change in the amount of current flowing.
Fiber Optic Microphone
Fiber-optic systems, which use super-thin strands of glass to transmit information instead of metallic cables, have revolutionized the field of telecommunications in recent years, including microphone technology.
Unlike conventional mics, which are often large and send an electrical signal, fiber optic microphones can be very small, and they can be used in electrically sensitive environments.
They can also be produced without metals, which makes them especially useful in magnetic resonance imaging (MRI) applications and other situations where radio frequency interference is a problem.
A dynamic microphone takes advantage of the electromagnetic effect.
When a magnet moves past the wire (or coil of wire), the magnet induces a current to flow in the wire.
In a dynamic microphone, when the sound waves hit the diaphragm, the diaphragm moves either a magnet or a coil, and the motion creates a small current.
Electret microphones are the most widely used microphones on earth.
Because they are cheap and relatively simple, electric microphones are used in cell phones, computers, and hands-free headsets.
An electret microphone is a type of condenser microphone in which the external charge is replaced by an electret material, which is by definition, in a permanent state of electrical polarization.
A laser microphone works by picking up vibrations off an airplane, such as a windowpane, for example, and sending the signal back to a photodetector, which converts the reflected laser light into an audio signal.
When the sound hits the window glass, the sound bends and causes the laser beam to bend, which can be translated into sound using a photocell.
In recent years, scientists have developed a new type of laser microphone that works by streaming smoke in a laser beam aimed at a photocell, which is then converted to an audio signal.
If you’re looking to record sound that’s located on the front and the side of the mic – but not behind it – the cardioid microphone is for you.
A polar plot for the gain of the heart-shaped, highest sensitivity cardioids is located directly in front of the mic, and slightly to the side.
Because of this, cardioid mics are ideal for recording live performances without picking up too much crowd noise.
Furthermore, many handheld microphones used to amplify vocals are cardioid mics.
Certain crystals change their electrical properties as they change shape.
By attaching the diaphragm to the crystal, the crystal will create a signal when sound waves hit the diaphragm.
As you can see, almost every technology imaginable has been harnessed to convert sound waves into electrical signals.
The one thing it has most in common is the diaphragm, which collects sound waves and creates motion in whatever technology is being used to create a signal.
A condenser microphone is basically a capacitor, with one capacitor moving in response to sound waves.
This motion changes the capacitance of the capacitor, and this change is amplified to create a measured signal.
Condenser microphones usually require a small battery to provide the capacitor voltage.
In a ribbon microphone, a thin ribbon – usually aluminum, duralumin, or nanofilm – is suspended in a magnetic field.
Sound waves move the ribbon, which changes the current through the band.
Ribbon microphones are two-way microphones, which means they pick up sound from both sides of the mic.
The RCA PB-31 was one of the first band microphones.
It was produced in 1931 and changed the audio and broadcast industry by setting new standards for sound clarity.
Several other microphone makers make comparable models, including the BBC-Marconi Type A and ST&C Coles 4038.
Based on the characteristics of the sound vibration reception pattern on the microphone, it consists of:
Omnidirectional Microphones can pick up sound from all directions with the same quality.
So it’s suitable for recording orchestras or choirs and is commonly used for live music in the studio because it requires the sound of the room too.
Unidirectional microphones have a very good sound capture sensitivity from one direction only.
It’s so named because the response form is similar to the shape of the heart (cardio in medical terms).
The microphone with polar pattern cardioids is very sensitive to the sound source from the front and less sensitive to the sound from behind.
This type of microphone is more directional than the cardioid.
So when the microphone is turned towards the sound source, the annoying sound (usually located off-axis) tends to be muted.
This polar pattern is similar to the polar pattern for hearing our ears, where we often change the direction of our head to make it clearer for the sound we want to hear.
Bidirectional microphones are sensitive to the sound from the front and the back just as strongly but this mic character rejects the sound coming from the side.
This type is not commonly used in live studios but is often used in making the Blumlein pair effect (stereo recording).
Types of Microphone Based on Their Uses
It’s usually used by one person, it’s a one-man microphone.
It’s generally small and equipped with a clamp or a flexible system when used.
This is the kind of microphone used by reporters, pilots, presenters, announcers, and the likes.
This type of microphone is used for recording.
There are many sound recording scratches and the most common one we find is in the music industry.
The recording microphone is very sensitive and has little noise.
The type of microphones used is usually a condenser or piezoelectric microphone.
This s generally used in large locations such as open spaces, large auditoriums, and also during ceremonies in the field.
Generally, this type of dynamic microphone has thick and dominant sound characteristics at low and medium frequencies.
How Does Wireless Microphone Work?
In the wireless microphone system, there are sets of electronic devices that act as an intermediary or liaison medium for signals sent using a transmitter and receiver using an air medium known as Radio Frequency (RF).
This radio frequency functions as an audio carrier (signal carrier) which is infiltrated with the radio signal.
This radio band with a certain frequency range sends audio signals from the microphone transducer.
In detail, you can see how the microphone below:
When we speak, our voice will form sound waves and go to the microphone
In the microphone, these sound waves hit the diaphragm (diaphragm) which is a very thin plastic membrane.
The diaphragm will vibrate according to the sound waves it receives and the coil of wire (voice coil) located on the back of the diaphragm will vibrate according to the vibration of the diaphragm.
A small permanent magnet (fixed) surrounded by the coil will create a magnetic field as the coil moves.
The movement of this voice coil in this magnetic field will generate an electric signal.
The resulting electrical signal then flows to an amplifier or voice recorder.
Wireless Microphone Frequency Bands
There are frequency bands used in wireless microphones that use the VHF (Very High Frequency) band and the UHF (Ultra High Frequency) band.
These two radio bands have their own privileges and there are also some disadvantages.
VHF (Very High Frequency)
VHF (Very High Frequency) has the character of being able to transmit far in the air and even has a wider range of UHF frequencies, but the VHF frequency is for use in places with many obstacles such as buildings, trees, walls, and obstructions.
The VHF frequency has a frequency rating of between 136 to 174MHz.
VHF is more suitable for areas where there is vegetation, where signals can pass through objects.
For this reason, VHF radios are ideal for outdoor use.
The VHF range of radio spectrum is a band that extends from 30 MHz to 300 MHz.
The wavelengths corresponding to this limit frequency are 10 meters and 1 meter.
In the VHF band, electromagnetic fields can be obtained by the earth’s ionosphere and troposphere.
Ionosphere propagation occurs routinely at the lower end of the VHF spectrum, especially at frequencies below 70 MHz.
In this mode, the communication range can sometimes be extended across the earth.
The troposphere can cause communication, ducting, and scattering, extending its range significantly beyond the visual horizon.
Auroral, meteor-scatter, and EME (earth-moon-earth, also called moonbounce) propagation takes place on occasion, but these modes do not offer reliable and attractive communication especially for amateur radio operators.
The VHF band is popular for two-way radio cellular communications.
Much of the satellite communication and broadcasting takes place on VHF.
Wideband modulation is used by several services, the most common example being fast-scan television broadcasts.
Typical industries that use these frequencies include farming and agriculture, road and bridge construction, volunteer public safety, paging systems, and long-haul trucking services.
UHF (Ultra High Frequency)
UHF (Ultra High Frequency) can transmit through physical obstacles, such as buildings, trees, cliffs, or just a wall.
UHF frequencies have a frequency rating of between 330 and 400 Mhz.
There are also those at the frequency level of 400 to 520MHz, but this frequency and higher more are often used by government officials because special permits are needed.
UHF (Ultra High Frequency) generally offers better building penetration and is therefore suitable for indoors as well as for high building density areas (cities).
Where applications require a combination of indoor and outdoor use, UHF radios are preferable.
The UHF range of the radio spectrum is a band that extends from 300 MHz to 3 GHz.
The wavelengths corresponding to this limit frequency are 1 meter and 10 cm.
In the UHF band, signals from earth-based transmitters are not returned by the ionosphere to the surface; they always come into space.
In contrast, signals from space always penetrate the ionosphere and reach the surface.
Global “shortwave” propagation is familiar to users of unknown lower frequencies in UHF.
The troposphere can cause bending, ducting, and scattering in UHF, extending the range of communications significantly beyond the visual horizon.
Auroral, meteor-scatter, and EME (earth-moon-earth, also called moonbounce) propagation are sometimes observed, but these modes do not offer reliable and attractive communication especially for amateur radio operators.
At the top of the band, the waves can be focused or collimated by parabolic antennas of modest size.
The UHF band is widely used for satellite communications and broadcasting, in telephone and cellular paging systems, and with third-generation (3G) wireless services.
Due to the high frequency and very wideband (2.7 gigahertz range from low end to high end), wideband modulation and spread spectrum modes are practical.
Typical industries that use these frequencies include manufacturing, factories, and warehouses; hotels, hospitality, and retail stores, building construction, schools, dorms, and education facilities and healthcare, hospitals, and care homes
What is the difference between VHF (Very High Frequency) and UHF (Ultra High Frequency)?
VHF radios have been around for a long time and are quite cheap compared to UHF.
Because of this, there are many existing VHF radios in comparison to UHF.
Pair this with the fact that VHF has a narrower spectrum and fewer channels, which leads to congestion and a greater chance of having interference from other radios in the area
The higher frequency of the UHF radio directs to the shorter antenna, allowing manufacturers to produce more compact models.
This is desirable as a smaller model that is more portable and less awkward to manipulate.
Even though both types of radios can reach great distances, VHF radios suffer from signal degradation due to internal resistance.
These obstacles can range widely from mountains, hills, trees, and even buildings.
This will reduce the VHF radio range greatly, especially in urban areas.
UHF waves can penetrate these barriers much better and be affected less.
UHF radios often tend to consume their battery much faster than VHF because of the higher frequencies used.
This may be bad for people who are away from the charging station for an extended period of time.
Both radios are good but certain situations may cost you a better price than others.
In rural areas where there are few buildings and even fewer tall ones, you can settle for a cheaper VHF radio.
The fewer number of people in the area also reduces the possibility of distraction because there are fewer competing users
UHF radios are the best choice when you intend to use them within city limits where you are surrounded by many tall buildings and your signal is expected to pass through several walls
The wider UHF frequency spectrum also reduces the possibility of interference from other users, which is very likely due to a large number of people in a relatively small area
Regulation of Wireless Microphone Frequency Bands
Wireless microphones and similar devices are designed to tune and operate on specific frequencies known as the “Spectrum Band”.
Most wireless microphones today operate in various parts of the broadcast television band that are unused, including the VHF and UHF channels.
The FCC (Federal Communications Commission) allows wireless microphones to operate either on a license basis or not and has limited the amount of spectrum available to wireless microphone users.
To determine whether a transition affects the continued use of a particular wireless microphone, operators need to know the specific frequency their microphone uses.
Contacting the manufacturer is perhaps the most effective way to determine if a particular wireless microphone is affected by a transition and may need to be modified or replaced.
Also, information about the frequency used may be provided in the user manual of certain models.
In particular, the FCC allows users to continue operation on the 600 MHz service band under certain conditions until July 13, 2021.
However, the user must not cause harmful interference, either to the operation of existing broadcast television or to the operation of the 600 MHz service wireless license receiver in the band.
Transition out of the 600 MHz Band
To meet the growing demand for wireless broadband services nationwide, the FCC recently auctioned off the spectrum that has been licensed to broadcast television stations operating on TV Channels 38-51.
The auction result (completed April 2017) affects the availability of spectrum for the operation of wireless microphones at the 600 MHz frequency corresponding to the TV channel, in particular, the frequency 614-698 MHz.
Most of this 600 MHz frequency has been reused for the wireless operation of the new 600 MHz service (in particular, the frequencies 617-652 MHz and 663-698 MHz).
Prohibition on use of the 700 MHz band
In 2010, the FCC prohibited the use of microphones and wireless devices on unused broadcast channels in the 600 MHz service band and the 700 MHz band – particularly in the frequencies between 698 and 806 MHz.
This was done because use may cause harmful interference to disrupt or degrade communications in spectrum bands that have been released for use by public security networks and licensed commercial wireless services.
In conclusion, users of wireless audio equipment such as microphones, in-ear monitoring systems, and public announcement systems can only operate at frequencies: 520 – 694 MHz and 1790-1800 MHz.
In particular, almost all of the spectrum in the 600 MHz band has been reused and wireless microphones operating on the frequency must stop operating before July 31, 2021.
Also, wireless microphones are prohibited from operating in the 700 MHz band, which is reserved for public service entities such as police, fire, and emergency services, as well as for some commercial wireless broadband service providers.
If using Wi-Fi and Bluetooth, the wireless microphone frequency bands it can work at are either between 915 – 928 MHz, 2.400 – 2.4835 GHz, or 5.725 – 5.875 GHz.
This change does not necessarily affect all wireless audio equipment, as some of them are already working at a predetermined frequency.
Some tools can work in a wide selection of frequencies so that in this case the user only needs to change the frequency setting.
Unfortunately for those who use wireless audio whose transmission cannot be changed according to the existing regulations, they have to buy a new device.