Why Is UHF Spectrum so Important for Wireless Microphones?

Marc Henshall | 12/08/2015

For wireless microphone systems to work, we need  access to clean RF (radio frequency spectrum) - this much is obvious.  What is less well known or understood, is which bands – or sections – of  spectrum are best suited to the operation of wireless microphone and  in-ear monitor systems.

We can't, unfortunately, just use any  spectrum – there are certain physical limitations that leave us with a  clear choice of limited, but effective frequencies that work best for  our application. The most popular bands used for wireless microphones  over the last 50 years or so are referred to as UHF and VHF frequency  bands; UHF (Ultra High Frequency) in particular is the preferred space  in the UK.

uhf-spectrum-importance

Why UHF?

Although  we cannot directly compare radio frequencies to sound waves, one  characteristic they do share some similarity with is wavelength. Much  like sound waves, lower frequencies have a longer wavelength, and,  therefore, their propagation characteristics are stronger, which means  they penetrate surfaces better and traverse greater distances without  the need for a boost.

In a nutshell, UHF bands offer the largest  quantity of good quality spectrum at the best frequencies required for  large professional events.

Additionally, we can easily account  for TV interference in the UHF bands as it is predictable - we cannot  say the same for other parts of RF spectrum as these are often  de-regulated and shared by technology such as WiFi.

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Important changes to UHF Spectrum that affect you.

For  years, professional wireless microphones and in-ear monitor  systems happily shared UHF spectrum from 470 - 865MHz as a secondary  user alongside the transmission of analogue television. Recent years,  however, have bought about remarkable changes that significantly reduce  our access to the all-important UHF space.

The short story is,  back in 2003, the UK government announced it would be switching  traditional analogue television services to digital. The immediate  assumption was that this process would free up large portions of  spectrum, and subsequently, it could be sold for a profit to the highest  bidder. This process, and the income it generated for the UK Treasury  became known as the Digital Dividend Review (DDR). Inevitably, with the  rise in demand for mobile broadband, the majority of auctioned spectrum  was re-allocated for use by the mobile industry to deliver next gen 4G  services.

The first significant portion to go was the 800MHz  band, but it won't be much longer before 700MHz suffers the same  fate. To really bring the point home, it takes us from this:

spectrum-before-ddr

UHF  spectrum before DDR - (Green represents spectrum available to wireless  microphone users. Yellow is dedicated space for PMSE. Blue is  unlicensed, deregulated spectrum)

.....To this

spectrum-after-ddr

(Post DDR UHF with red representing the loss of 800MHz and 700MHz)

As  the above charts demonstrate, the space available to us has reduced  significantly, and while there is space left for now, a pattern is  clearly emerging.

Pac-Phone

Mobile is important too!

From  what we've described so far, it could be easy to assume we're anti  mobile phones - we're really not. We understand the need for internet  access on demand; the benefits this brings consumers, and the  contribution instant access to information has made to our lives.  However, pursuing with a strategy of expansion at all costs, simply  isn't viable.

You can't get away from the fact that spectrum is  essentially a natural resource – just like oil or gas – and if we  continue to consume it at the rate we are, we will eventually run out.  The harsh truth for our industry in-particular is that while the demand  for wireless microphones continues to rise, the amount of space  available to reliably operate them in is actually decreasing.

Ironically,  the prospect of a severely impoverished wireless microphone operating  space actually affects the mobile industry too:

Think about it,  what do people use their mobile phones for (other than to make calls)?  They consume content, right? The very same content that relies on  wireless microphone systems to meet production value expectations. It  might not be obvious to the average consumer, but wireless systems are  everywhere when it comes to producing TV, video, live music shows,  theatre productions, and even YouTube videos from the increasing number  of 'YouTube stars'. To remove wireless microphones from the equation  would mean setting production values back by half a century. This would  make streaming HD content on your phone somewhat less appealing, don't  you think?

The point is, changes to wireless spectrum affect  everyone. Therefore, it is not the sole responsibility of any one  industry or institution to take the entire burden. Demand for spectrum  certainly isn't going anywhere; what's certain is that we need to  achieve more with less (and that goes for everyone). It is in the  interest of new users to recognise, respect, and co-exist with wireless  microphone users to ensure we satisfy modern requirements.

Phones-Statistic

What we're doing to help: spectrum efficiency

One  way we're doing our bit to ensure a more sustainable future is through  spectral efficiency - a journey that started with our flagship wireless  systems, Axient.

Axient pioneered a range of new to the world  technologies – partly centred on the needs of engineers, but also  offering truly exceptional RF performance through features such as  automatic interference detection and avoidance. While limited to our  flagship Axient system at first, our intent was always to replicate  these features – wherever possible – throughout the entire Shure  wireless portfolio. Subsequently, many of the advanced wireless  technology features originally exclusive to Axient are now found across  our wireless portfolio – right down to our consumer level options. Given  the uncertainty of a congested RF landscape, having a spectrally  efficient wireless system is essential – no matter what your budget.

What you can do to help

The  fight to save the future of wireless microphones for future generations  doesn't end with manufacturers; you can do your bit too. Here are three  ways you can get involved:

1. Spread the word

Education  is key to ensuring a sustainable future for all wireless spectrum  users. To help raise awareness of wireless technology and the ongoing  changes, we set up LosingYourVoice.co.uk

The initiative contains a  crucial overview of the current RF landscape and links to useful  resources. By sharing this website, you can help us ensure a more stable  future for wireless audio.

Visit Losing Your Voice

2. Become a Wireless Expert

Parallel  to Losing Your Voice, is our Academy training platform. One of the key  contributions users can make to the wider industry is to learn how to  run their wireless rig as efficiently as possible. Check out our  Wireless Mastered seminar and Spectrum Management Masterclass (How to  master Shure's Wireless Workbench 6 coordination software) to help you  run your next show with complete peace of mind.

Visit Shure Academy for upcoming dates.

3. Support with BEIRG

Engineers and audio industry  professional wishing to get in the trenches so to speak can get involved  with The British Entertainment Industry Radio Group BEIRG.

BEIRG is an independent and non-profit making association, working for the benefit of all those who use radio spectrum.

Visit their website for further detail.

Have your say

Have something to add to this article? How are the changes to RF spectrum affecting you?

Marc Henshall

Marc forms part of our Pro Audio team at Shure UK and specialises in Digital Marketing. He also holds a BSc First Class Hons Degree in Music Technology. When not at work he enjoys playing the guitar, producing music, and dabbling in DIY (preferably with a good craft beer or two).