Be the Expert: Wireless Microphone Systems | Petra.com

Mic check 1, 2: Checking the ins, the outs, and the commonly asked questions about wireless microphone systems

Wireless microphone systems are common today. But once upon a time, wired was the only option. Microphones, or the idea for them, have been around since the mid 1850s. Many noted inventors of the day worked on concepts. In 1877, Emile Berliner invented and patented the carbon-disk or carbon-button wired microphone.

Alexander Graham Bell liked it so much that a year later he bought Berliner’s patent and used the device in his telephone. Shortly thereafter, a dispute over the patent. It was finally settled by the U.S. Supreme Court in 1892. The result was that Thomas Edison was given credit for the carbon microphone. However, at least one Berliner idea still remains undisputedly his—the lateral-cut disc record, or what we know today as the phonograph record.

Baby steps toward wireless

According to musiciansfriend.com, wireless microphone systems started appearing in the mid 1940s. They were DIY kits for hobbyists. The Shure Brothers claim to develop the first wireless system for performers. It had a range of 15 ft. In 1957, the forerunner of Sennheiser released a system with a range of 300 ft.

In 1964, electrical engineer Raymond Litke obtained Patent 3,134,074 for a microphone transmitter having a lavalier type antenna.

That 1964 patent’s opening paragraph contains an apt summary of the main advantages of wireless microphone systems, still valid today:

• User is free to move about without trailing wires
• Transmitter, power supply, and antenna can be inconspicuously worn
• Has high fidelity response

Later that same year, Vega Electronics marketed a version of his system. Sony introduced its first system in 1958. Nady developed “companding” technology in the mid 1970s. And finally in 1996, an Emmy was presented to Nady, CBS, Sennheiser, and Vega for “pioneering the development of the broadcast microphone.”

How today’s wireless microphone systems work

A wireless microphone system has three distinct components.

1. Microphone or pickup device
2. Transmitter
3. Receiver

The microphone sends its signal via wire or hard contact to the transmitter. The transmitter converts that to a radio signal and broadcasts it. The receiver picks up the radio signal then changes it back to an audio signal. That audio signal is then fed via cable to a sound system, usually a mixer or sound board. Therefore, a wireless microphone system is distinct from the rest of a sound system.

How wireless microphone systems can vary from each other include:

• Which radio frequency or frequencies are used
• Kind of microphone
• Whether the system is analog or digital

Beyond these basic differences, there are additional features to consider such as:

• Number of antennas
• Ability to choose radio frequencies
• Operating range

What wireless microphone frequencies are legal?

One of the first things your customers will notice is that systems are generally labeled either VHF (49–608 MHz) or UHF (470–805 MHz). The FCC regulates which radio bands are available for different devices or broadcasters to use. Over the past few years, they’ve auctioned off a number of bands in the UHF spectrum. Currently, the FCC has designated these frequencies for use by wireless microphone systems: 

• VHF and UHF frequencies on TV channels 2­–36, which fall below 608 MHz
• Certain frequencies in the 600 MHz guard band: 614–616 MHz
• Certain frequencies in the 600 MHz duplex gap: 653–657 MHz for licensed use or 657–663 MHz for unlicensed use

Licensed operators include “licensees of AM, FM or TV stations, broadcast networks and cable-television system operators, and venue owners/operators and professional sound companies that routinely operate 50 or more wireless mics for events and productions at large venues such as large sports stadiums and arenas, music centers, or major theaters.”

The FCC also opened up some bands that are not TV bands:

• Licensed operators: 169–172 MHz band, portions of the 900 MHz band, and the 1435–1525 MHz and the 6875–7125 MHz bands
• Unlicensed operators: 902–928 MHz band, the 1920–1930 MHz band, and portions of the 2.4 GHz and 5 GHz bands

Compliance went into effect July 13, 2020. But auctioned frequencies (617–652 MHz and 663–698 MHz) are used by a number of older wireless systems. Consequently, if your customers are caught using those bands, they can be forced to cease and desist. So be sure to ask your customers to review their current systems!

VHF vs UHF wireless microphone systems

Advantages and disadvantages of VHF systems

• Less expensive
• Operate on a single frequency channel
• Ideal for use in small spaces with fewer competing signals
• Susceptible to interference from assistive listening wireless systems, walkie-talkies, RC toys, FM radio stations and TV channels 2–6

According to sweetwater.com, high-band VHF frequencies 169–172 MHz and 174–216 MHz are FCC-approved for wireless microphone users. The first grouping is called “traveling frequencies” and are theoretically good throughout the US. The second group is used for broadcast and commercial production. This is where the highest quality audio and transmission can be found when it comes to the VHF bands.

Advantages and disadvantages of UHF systems

• Generally used by higher-end systems so tends to be more expensive
• Available as single frequency units but many have the ability to choose from multiple frequencies, so they are less susceptible to interference
• More frequency choices also mean more systems can operate simultaneously
• Uses more power resulting in shorter battery life
• Ideal use in large spaces or in areas where the chance of interference is greater

How to choose between a VHF wireless microphone system and a UHF wireless microphone system

To sum up, as sweetwater.com suggests:

“Consider VHF if:

• …less than 5 systems at the same time
• …performing in “open” radio environments, free from interference
• …do not have line of sight between transmitter and receiver
• …budget is limited

“Choose UHF if:

• ...travel and perform in several different cities
• …use more than 5 or 6 wireless systems at the same time
• …play in “crowded” radio environments, meaning there is a strong presence of other radio activity all around your location
• …willing and able to spend a little extra”

Kinds of wireless microphones

Microphone choices include handheld, lavalier/lapel, headset, and instrument pickup. Some systems come with a single microphone while others may allow you to mix and match.

• Handheld mics often have the transmitter built into the handle for ease of use.
• Lavalier or lapel mics use a small cable to connect to a bodypack transmitter. They attach to clothing and are available in many different shapes and sizes.
• Head-worn mics use a headband of some sort to hold them in place and are ideal for active performers. They too connect to a bodypack transmitter.
• Special clip-on instrument mics feed a bodypack transmitter. A guitar pickup plugs into an instrument’s output jack and then plugs into a bodypack. Furthermore, some pickups even have the transmitter built in.

Pickup pattern also defines microphones.

• Omnidirectional picks up sound from all directions and are ideal for quiet environments
• Cardioid or directional picks up sound primarily from the front but also some from the sides so they are ideal for use in noisier environments
• Unidirectional picks up sound from the front only so they too are ideal in noisier environments

Handheld microphones

When it comes to handheld microphones, there are two basic kinds—dynamic and condenser. Not only are the operating principles distinctly different (read here for more information on that), they should be used for distinctly different purposes.

• Dynamic: Rugged. Inexpensive. Ideal for loud, strong sounds in a live setting or outdoors. Does not require supplemental power.
• Condenser: More expensive and sensitive. Better for studio use. Ideal for more complex, higher frequencies. Requires battery phantom power or preamplification.

UHF analog vs. digital wireless systems

Both kinds of systems convert sound into radio waves. The difference is what is transmitted through those waves. Analog systems often use “companding” to compress transmitted signals to use up less radio wave space due to the limited number and capacity of wireless channels. The receiver then expands it back. Consequently, this can create noise.

Digital systems, however, convert the audio signals to digital ones and zeroes. This completely eliminates radio frequency interference and signal degradation. These signals can also be encrypted. But digital units take up more frequency space and can introduce latency or lag. They are also more expensive. But for setups where more than 16 microphones are used, they are the preferred choice.

However, as sweetwater.com notes, “High-quality analog wireless systems can rival digital wireless systems in audio quality and ease of use, but, as always, you should factor in all of your needs when choosing the best wireless microphone system for you.”

Additional system features to consider

One of the biggest problems with wireless systems is dropout. When the microphone’s transmitter and receiver’s antenna lose contact with each other, dropout occurs. Reflective surfaces and physical obstructions are often to blame. As a result, this is where the “diversity” feature can help.

• Diversity involves the use of two antennas. The simplest form uses diversity circuitry. However, a true-diversity receiver is more sure-fire. It has a radio module for each antenna and will auto select the one with the strongest signal. In contrast, a system with just one antenna is called a non-diversity system.
• Frequency agility is a feature that allows the user to pick and choose from multiple frequencies to avoid interference from other systems or devices. This is ideal when there are many microphones in play, as each should have its own distinct frequency. A system with automatic frequency selection eliminates the guesswork.
• Operating range. Most experts recommend choosing a system that claims twice the distance of what you need.
• Display legibility. How easy is it to read? Does it indicate battery life? Signal strength? Which channel is being used?
• Kinds of receiver outputs. Are they compatible with the mixer system with which the microphones will be used?
• Microphone controls. Are there separate power and mute buttons? Because it’s handy to keep a microphone’s frequency on yet mute the sound for sneezes or private conversations.
• Rechargeable batteries. Some systems use rechargeable batteries while others use standard disposable ones.

4 commonly asked customer questions

1. Can a wireless mic work with any receiver?

No. You cannot mix and match. The transmitter and receiver are specifically tuned to each other. Plus, transmission technologies and even frequency designations vary from manufacturer to manufacturer. Certainly always use matching components from the same company.

2. Can you plug multiple mics into one receiver?

No. Each microphone has its own transmitter which talks only to its matching receiver. Above all, if multiple microphones were able to be fed into a single receiver, signal chaos would ensue.

3. How can I avoid wireless microphone interference?

There is no easy answer to that. That’s because there are many variables and requires a lot of troubleshooting. We suggest you check out these articles by mspot.com, rfvenue.com, and shure.com.

4. What about wireless Bluetooth microphones?

Bluetooth microphones are their own entity. They do not work like traditional wireless systems work and are not in the same category. They are often used to connect directly to computers, speakers, amps, karaoke systems, or PA systems—assuming those devices accept Bluetooth signals. Furthermore, some handhelds even have their own speakers built in!

Cutting the cord by using wireless microphone systems

Wired systems are the gold standard of audio in terms of sound quality. There is no compression and there are no radio transmissions in play. However, cabling is often not practical.

Here at Petra, we recognize the place of both. So for your wireless microphone systems and hardwired microphones, turn to Petra. We’ve got all the channels covered.