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Wireless microphones and frequencies

Wireless microphones and frequencies

mercoledì 10 maggio 2017 da Lizanne | Bax-shop

If you're thinking about investing in a wireless microphone or another wireless system, you'll find out there is plenty to consider when making the right choice. There is quite a bit of contradictory information online with regards to the use of wireless systems, but never fear, we're here to help! This article contains information about frequencies in general as well as which frequencies are applicable to you and your personal situation. After reading this article, you will be able to make an informed decision and invest in a flexible system that you can enjoy for years to come!

Choosing the right wireless microphone

If you’re planning to purchase a wireless microphone, we recommend reading the Wireless Microphone Buyer’s Guide first. It contains information on different types of microphones including handheld, headset and lavalier models as well as the connection possibilities and the various frequencies. If you want to find out even more about wireless frequencies, read on below.

Microphones, audio signals and radio signals

Technically speaking, a conventional microphone converts sound into an electric signal, which is then sent through a cable to a sound system. A wireless microphone, however, converts an audio signal into a radio signal that is sent through the air to a receiver via a transmitter. The receiver is connected to a sound system and the transmitter can either be integrated into mic itself (in the handle of a handheld mic, for instance) or worn as a beltpack (for headsets and wireless instrument microphones). All wireless systems have a receiver that is connected to a sound system by means of a cable and converts the radio signal into an audio signal. Wireless in-ear systems work exactly the opposite - the transmitter is connected to the mixer and the musician or speaker wears a beltpack receiver.

Even though wireless systems solve the age-old problem of tangled, cumbersome cables on stage, it is not 100% problem-free. Each wireless system sends and receives data at a specific radio frequency so it's extremely important to choose a system that operates on the correct band for your situation and location. Combining random frequencies can cause problems because different systems compete and interfere with each other, which can cause disturbances like noise and dropouts. The UHF band is shared with telecom providers for wireless internet and digital TV stations, so it's vital to know which frequencies you're allowed to use and which ones may cause interference due to a large number of other users.

Intermodulation

Intermodulation is caused by non-linear behaviour due to signal processing of wireless microphone systems at specific frequencies. In other words, if signal 1 is sent at 824.1 MHz and signal 2 at 824.7 MHz, then intermodulation distortion (IMD) will occur both in and outside these frequency bands because the frequencies react to one another, causing small peaks and interference when outside their range. To prevent this, maintain a margin between the two frequencies. Wireless systems with multiple channels usually do this automatically. The more systems you use simultaneously, the greater the margin needs to be. If there were a third microphone added to the example mentioned above, then the margin would need to be twice as big. Another thing to keep in mind is that if a wireless system is equipped with 16 channels, it does not mean you can use 16 microphones simultaneously.

Multiple wireless microphones at once

There are countless wireless microphones on the market that vary greatly in price and functionality. One of the most important factors to take into consideration when investing in a wireless system is how many additional microphones it can facilitate at once. Budget systems usually operate on a fixed frequency, but buying two sets to use at the same time is not a viable solution. More expensive systems usually allow you to configure multiple frequencies so that you can use multiple systems at the same time. Which frequency bands the system operates on is usually indicated in the name of the product; for example, the Sennheiser XSW 2-835 (E: 821-865). Please note, each brand has their own way of indicating the frequency. Professional systems often come complete with software so you can see which frequencies are available in your location. Sennheiser offers the Wireless System Manager and Shure offers the Wireless Workbench. Sometimes, brands also offer free tools that help you find available frequencies in your areas, such as Sennheiser's online FrequencyFinder tool and the Frequency Xpert app.

Frequencies, VHF and UHF

The most commonly-used radio frequencies that most wireless systems operate on are roughly divided into two groups:

- VHF (Very High Frequency): 30 MHz (30,000,000 Hz) to 300 MHz (300,000,000 Hz)
- UHF (Ultra High Frequency): 300 MHz (300,000,000 Hz) to 3000 MHz (3000,000,000 Hz)

Most wireless microphones and monitor systems operate on the UHF band, which is split up into channels 21 through 70 (see figure 1). Each channel covers 8 MHz except the ISM band and the 1G8 bands. This distribution is used worldwide to indicate which frequencies are allowed for use per region.

In many cases, you will need a licence to operate a wireless microphone system. You can request a licence in the country where you'll be using the system. The rules vary greatly per country, so make sure the system is permitted for use in the region where you will be using it.

Licence-free frequencies

There are a number of frequency bands that can be used without a licence throughout Europe and even the world. For starters, there's something known as a band gap or Duplex Gap (822 - 830 MHz), which is basically a buffer between the uplink and download frequencies belonging to mobile providers. It's a very narrow gap, which makes it unsuitable for using multiple systems at once. There is also a higher risk of intermodulation because there are so many mobile phones in the area. This also goes for the 863 - 865 MHz band, which is just above the frequency range used by mobile phone providers. The 822 - 832 MHz band can be used pretty much throughout Europe without a licence.

Systems that operate on the 2.4 GHz band (2400 - 2483.5 MHz) have a great advantage in that they can be used anywhere in the world without a licence. Unfortunately, this also means it's a very popular frequency band that is used for anything from microwaves to connectivity services like WiFi and Bluetooth. Many consumer appliances that have been built in the last five years now operate on the 5 GHz band, which will hopefully create some room on the overcrowded 2.4 GHz band in the future. Another disadvantage of this frequency is that it has a very short wavelength, and the shorter the wavelength, the smaller the range. You'd probably only manage a range of up to 30 metres and would only be able to use six wireless microphones or in-ear systems simultaneously on the 2.4 GHz band.

Further developments

As a result of new developments in mobile technology, the frequency landscape is constantly changing and making more and more room for wireless audio. In early 2016, the 800 MHz range was designated for use throughout Europe for mobile phone providers, so microphones that used to operate on that frequency band will no longer work. Now, the same thing is likely to happen for the 700 MHz band. It is projected that by the year 2020, any frequency between 694 and 790 MHz will no longer be available for wireless microphones.

Licences in the United Kingdom

In the UK, you can use the following frequencies without a licence:

863 - 865 MHz, max. 10 mW e.r.p.
173.8 - 175 MHz, max. 50 mW e.r.p.

There are two types of licences obtainable in the UK, both of which can be requested via the OFCOM (Office of Communications) website.

With a Standard Licence, you request permission to use a fixed frequency in a fixed location at a fixed time. The advantage of this is that OFCOM coordinates the frequency band in such a way that users don’t interfere with one another. The frequency bands available for this type of licence are 470 - 790 MHz and 1780 - 1800 MHz.

With a UK Wireless Microphone Licence, you receive permission to use a frequency band for the duration of 1 or 2 years. Once licensed, you can use this frequency band anywhere in the United Kingdom. The use of these bands is not coordinated by OFCOM, so some interference from other users may occur. Unlike a Standard Licence, you are allowed to switch to another frequency with the UK Wireless Microphone Licence. The available frequency bands for this type of licence are UHF channel 38 (606 - 614 MHz) and VHF (175.250 - 209.800 MHz).

Licences for The Netherlands

In the Netherlands, you can use the following frequencies without a licence:

195 - 202 MHz, max. 50 mW e.r.p.
470 - 604 MHz, max. 50 mW e.r.p.
614 - 694 MHz, max. 50 mW e.r.p.
823 - 826 MHz, max. 20 mW e.i.r.p. (for handheld), 100 mW e.i.r.p. (for beltpack)
826 - 832 MHz, max. 100 mW e.i.r.p.
863 - 865 MHz, max. 10 mW e.r.p.
1785 - 1805 MHz, max. 20 mW e.i.r.p. (handheld), 100 mW e.i.r.p. (beltpack)

The 470 - 694 MHz band is not fully available everywhere in the Netherlands as it is also shared with the digital broadcasting network. The use of frequencies for the broadcasting network differ per region. This means the availability of frequencies for wireless microphones is also different per region. If you’d like to know which frequencies can be used in any specific location in the Netherlands, use the Microfoonbanden app by Agentschap Telecom (Telecom Agency).

Licences for Belgium

As well as the 822-830 MHz, 863-865 MHz and 2.4 GHz bands, the 518-526 MHz and 534-542 MHz bands can also be used without a licence in Belgium. 606-614 MHz is reserved for radio astronomy. All other frequencies require a licence. You can request a licence at the Belgisch Instituut voor Postdiensten en Telecommunicatie (Belgian Institute for Postal Services and Telecommunication). You can download a list of the available frequencies per region.

Licences for France

In France, you can use wireless microphones and in-ear systems on the following frequency bands:

174 - 223 MHz, max. 50 mW e.r.p.
470 - 694 MHz, max. 50 mW e.r.p.
823 - 826 MHz, max. 20 mW e.i.r.p.
826 - 832 MHz, max. 100 mW e.i.r.p

As long as you do not exceed the maximum output, you do not need a licence to use these frequencies. If you require more output for a large-scale event, for example, then you can request a licence from the French government ARCEP (Audio Programme Making and Special Events), which is valid for a maximum duration of two months.

Licences for Germany

In Germany, you can use the following frequencies without a licence:

174 - 230 MHz, 50 mW e.r.p.
823 - 832 MHz, 100 mW e.i.r.p.
863 - 865 MHz, 10 mW e.r.p.
1785 - 1805 MHz, 82 mW e.i.r.p.
1795 - 1800 MHz, 20 mW e.r.p.

You will need a licence to use the 470 - 694 MHz band, which you can request by downloading a form at the official Bundesnetzagentur (Regulatory Authority for Telecommunications and Post) website. The licence is valid for a specific location only for a maximum of 30 days.

Licences for Sweden

In Sweden, you can use the following frequencies without a licence:

823 - 826 MHz, max. 10 mW e.r.p. (handheld), 50 mW e.r.p., (beltpack)
826 - 832 MHz, max. 50mW e.r.p.
863 - 865 MHz, max. 10mW e.r.p.

For the frequency bands below, you will need to request a licence from the Swedish government institution PTS.

174 - 240 MHz, max. 50 mW e.r.p.
470 - 694 MHz, max. 50 mW e.r.p.
1785 - 1800 MHz, max. 20 mW e.r.p., (handheld), 50 mW e.r.p., (beltpack)

Licences for Spain

In Spain, you only need a licence if you plan on exceeding the maximum e.r.p output level. You can request a licence on the website of the Spanish government. The maximum output levels per frequency are listed below:

174.100 - 179.300 MHz, max. 50 mW e.r.p.
188.100 - 194.500 MHz, max. 50 mW e.r.p.
470 - 786 MHz, max. 50 mW e.r.p.
823 - 832 MHz, max, 20mW e.i.r.p. (handheld), 100mW e.i.r.p. (beltpack)
863 - 865 MHz, max. 10mW e.r.p.
1785 - 1805 MHz, max. 20mW e.i.r.p. (handheld), 50 mW e.i.r.p. (beltpack)

Licences for Italy

In Italy, you only need a licence if you plan on exceeding the maximum e.r.p output level. You can request a licence on the website of the Italian government. The maximum output levels per frequency are listed below:

823 - 832 MHz, max. 10 mW e.r.p.
863 - 865 MHz, max. 10 mW e.r.p.
174 - 230 MHz, max. 50 mW e.r.p.
470 - 786 MHz, max. 50 mW e.r.p.
786 - 790 MHz, max. 12 mW e.r.p.
1785 - 1805 MHz, max. 20 mW e.i.r.p. (handheld), max. 50 mW e.i.r.p. (beltpack)

Border regions

The circumstances in border regions with regards to wireless microphone systems are very unique. You must adhere to the rules and use the permitted frequencies in the country you are physically in. This does not mean you may not experience interference and IMD from users on the other side of the border. Even if someone is using the same frequency as you with exactly the same system, chances are your continuous signal will be stronger and more stable than the 'rival' signal, which should keep IMD to a minimum.

In conclusion

Despite the fact that you should be able to make an informed choice based on the information above, the actual wireless system you decide on is still dependent on a number of factors. One of the most important factors is multiple users on the same frequency band. Large-scale events where multiple systems are in the air at once mean that a good allocation of the available frequencies is vital. Make sure you have the licence you need in order to prevent unexpected surprises!

Should you need help with your specific situation, please get in touch with one of our product specialists via telephone or e-mail. They are happy to advise you! You can find the contact information and opening times here.