The Advantages of Digital Wireless

Traditional analogue systems use a form of frequency modulation to transmit an audio signal over radio waves.

When you select a UHF frequency for your analogue wireless system to operate on (606MHz for example), this is the centre frequency – it is then modulated above and below. The speed at which it’s modulated is how the audio frequency is embedded in the radio wave. In layman’s terms, if you want to embed a 100Hz audio sine wave within a radio signal, you modulate around that centre frequency of 606MHz 100 times a second.

Each analogue wireless system consumes a chunk of radio spectrum due to the bandwidth required for the modulation. This usually results in a maximum of 12 systems reliably working together within your 8MHz channel 38 (for example) licence.

Digital systems on the other hand use a radio wave to transmit simple 1’s and 0’s. The audio is then embedded via an encoding method.

Digital systems only require a tiny slither of the available radio spectrum as no modulation is needed. In ideal conditions 20 plus systems can be deployed reliably together within an 8MHz channel. Some systems employ a high-density mode that increases channel count at the expense of transmission distance. In HD mode you can expect to achieve 60 plus systems working reliably within your 8MHz channel.

A common reply to this is: “I only need 8 channels” … That might be the case but what happens when another event starts in the conference room next door or a band turns up with half a dozen wireless IEM’s? Are there large video panels at the event? These radiate huge amounts of RF.

You may only need 8 channels of wireless but is there enough clean spectrum available for 6 analogue systems? You could reliably squeeze in more digital systems.

The FM radio signal used by analogue systems has a poor signal to noise ratio, increasing the chances of background noise or hiss. Compander circuits are used to improve this.

These compress the audio signal before transmission and use an expander circuit (in the receiver) to retrieve some of the pre-compression dynamics. Even the very best companders add artefacts to the audio signal. In more cost-effective systems the “pumping” effect of the compander can actually be heard in the audio. There is a noticeable “dulling of the sound” caused by the roll off in the high frequencies.

Digital systems have no need for companders so retain all of the nuances and dynamics of the original audio with no artefacts. The result? A much cleaner and purer sound.

Without the need for companders and other limitations of analogue circuitry, digital wireless systems have a vastly superior dynamic range. For example, Sennheiser’s new EW-D and EW-DX range have an audio input dynamic range of 134 dB which eliminates the need for sensitivity adjustments and preserves every detail. Meaning the system could capture the sound of a jet plane taking off without any distortion – easily giving you enough headroom for loud vocals!

Digital signals can be encrypted. This is vitally important for corporate use where confidential information is being transmitted over wireless microphones.

Users can rest assured that no one will “tune in” to their conversation. Unfortunately, this is not the case for analogue systems and is purely an advantage of digital wireless.

Digital wireless systems from the likes of Shure and Sennheiser utilise AES-256 encryption. This digital encryption method has been around for well over a decade and has proved to be reliable and secure.

Hopefully that makes digital wireless a little clearer? Until next time!

*Written for AC-ET by Steve Eaton | Senior Audio Sales Executive.