Wireless Systems and the 2.4GHz Frequency Band

When using any wireless system, whether it’s for wireless microphones, a wireless in-ear monitoring system or a cable-free instrument system, then you’ll have to work with radio frequencies. These are inherent to the way these wireless systems work, since wireless systems convert audio into code before sending it through the air in the form of a digital packet, so it can be picked up by a receiver where the information is decoded and converted back into audio. The radio frequencies available for this process aren’t infinite, and need to be shared with a range of other users. Since the traffic travelling via these frequencies is only getting busier, new innovations and developments are needed to make some extra room.

Frequencies
The VHF Band
The UHF Band
The 2.4 GHZ Band
The SENNHEISER D1 System
Triple Diversity
The Advantages of Digital Systems
Summary
See also…

Frequencies

The radio frequencies used by most wireless systems can be roughly divided into two groups:

VHF (Very High Frequency): 30 MHz (30.000.000 Hz) tot 300 MHz (300.000.000 Hz)
UHF (Ultra High Frequency): 300 MHz (300.000.000 Hz) tot 3000 MHz (3.000.000.000 Hz)

The UHF band includes the 2.4GHz band, which is also known as the WiFi band. WiFi doesn’t only work on the 2.4GHz band, but more and more often, it’s transmitted over the 5.0GHz band. Every band comes with its own scope, and therefore its own set of advantages and disadvantages.

The VHF Band

This band is used by FM radio, for maritime and aviation communications, military communications, police communications and civil communications (think taxis, amateur radio operators and wireless microphones). The biggest disadvantage of using this band is that it has a relatively narrow bandwidth that’s shared with a lot of signals that are often sent using really powerful transmitters.

The UHF Band

This band is used by a lot of different devices, so it’s really busy. Besides wireless microphone systems, the UHF band is used for digital television, wireless internet connections and mobile phones. While all that traffic is certainly a disadvantage when using the UHF band, a big advantage of using this band is that the frequencies within it have a really short wavelength, meaning that you can get away with using a relatively small antenna.

The 2.4 GHZ Band

The 2.4 GHz band, which is also used for network connections and a lot of other wireless equipment, can also be used for any compatible wireless microphone systems. A major advantage of using the 2.4GHz band is that, in principle, the bandwidth is unlimited, so multiple systems can work seamlessly alongside each other and in close proximity. The big disadvantage of using this band is that an unbelievable amount of devices will be using it too. This will include phones, laptops, tablets, wireless lighting systems, smart thermostats and other similar household systems. So, imagine using a microphone system in a large hall, packed with a crowd of 1,000 people all armed with mobile phones and probably a host of other wireless 2.4GHz-compatible gadgets.

The level of stability you get when using the 2.4GHz band depends on the manufacturer. When using a good system, you can usually quickly and inaudibly switch between available frequencies that are clean of any RF interference, so you’re working with a stable system.

Since a lot of wireless devices are starting to switch to the 5GHz band, there’s a big chance that the 2.4GHz band will get a lot quieter over the coming years. However, the disadvantage of using the 5GHz band is that, in theory, the signal isn’t able to travel that far, but the bandwidth is incredibly wide, which results in better signal stability. Because of this, it’s ideal for household systems and devices, so will probably be pushed more and more by the manufacturers of routers, phones and tablets.

Until the mass migration over to the 5GHz band has happened, 2.4GHz band users still need to take frequency traffic (depending mainly on the range of routers and so on) into account – especially during soundcheck. It might be that a 2.4GHz band system works perfectly during soundcheck, but as soon as the room is filled with a thousand smartphones, each searching for available space in the WiFi signal, it might start running into trouble.

The SENNHEISER D1 System

One of the manufacturers taking a deep dive into the 2.4GHz band is Sennheiser, the result of which is the D1 system. To counter any possible drop-outs and interference, this progressive system has been kitted out with a range of intelligent features.

Triple Diversity

To really ensure that their new system would be as reliable as humanly possible, Sennheiser developed their own Triple Diversity technology. This three-way approach is made up of antenna-diversity, frequency-diversity and time-diversity. Antenna diversity is a familiar feature of analogue systems where the receiver is fitted with two antennas and constantly measures the reception of both antennas so it can switch to the strongest at any moment, always guaranteeing the best signal.

Frequency diversity is new. This system continuously scans the environment, and if any interference is detected on the current frequency, it automatically switches to a different one. Time diversity is also new, where the D1 system uses two audio channels so that, as soon as one channel is compromised in any way, it can immediately and automatically switch over to the backup channel.

Another extra function, which was previously exclusive to the more expensive analogue systems from Sennheiser, is the ‘walk test’. With the help of this smart function, you can test the reception quality of the wireless connection in the space you’re working in. This way, you can check the range of the wireless connection and pinpoint any areas where the reception is poor or drops out completely.

The Advantages of Digital Systems

Digital systems do come with a few advantages that analogue systems just don’t. Because you’re using both a digital transmitter and receiver, the data is uncompressed, and therefore has a big dynamic range. The transmitter and receiver can also exchange data. For example: the display on the receiver might be able to show the microphone status, like the battery level and the microphone capsule that’s being used (the Sennheiser system is compatible with various different capsules, including the e835, e845, e865, e935, the e945 and the e965). And, when using multiple systems at the same time, it’s easy to see which transmitter is linked to which receiver.

Besides handheld microphone systems, Sennheiser also offers an instrument microphone system, a clip-on microphone system and a headset system. All of the D1 system transmitters are powered by standard AA batteries or the compatible rechargeable battery pack which is sold separately.

Besides the stabilising methods mentioned earlier, the Sennheiser D1 wireless system includes a few other smart functions:

Automatic setup: this function searches for all free frequencies, makes sure that the gain is set correctly, and tunes multiple systems to one another.
Built-in audio effects: this includes a de-esser, auto gain, 7-band EQ and a low-cut filter.
Adaptive Transmission Power: here, the receiver continuously informs the transmitter of how much RF power it needs to transmit to maintain a stable signal. The closer the transmitter is to the receiver, the less signal strength is needed. This saves on battery power and expands the transmitter range.
The whole system can be controlled via an Apple and Android compatible app.
Minimal latency.

Summary

When picking out a wireless system, it’s essential that you go for a system that’s able to hold its own in a wireless world that’s only getting busier. This applies to VHF and UHF systems, as well as 2.4GHz systems. Manufacturers like Line 6, Shure, AKG, Samson, Sony, Audio Technica and Sennheiser all offer systems that operate over the 2.4GHz frequency band. So if you do need to get a system that works over this licence-free band, then you’ll have plenty to choose from across an array of price ranges. All you need to be aware of is that all frequency bands come with both advantages and disadvantages, so make sure to pick a system that best matches up with what you need to use it for. Here, you’ll find all of these wireless systems complete with full specifications so you can make a fully informed decision.