/ Technology

What the *bleep* is spectrum?

Rainbow waves symbolising spectrum

With telecoms regulator Ofcom recently making a song and dance about its ‘largest ever single auction of additional spectrum’, we’re asking ‘what’s the big deal about spectrum?’

Ever asked a seemingly simple question expecting a simple answer, just to receive such a long-winded or complicated reply that you wished you’d never asked? Questions like: Why is the UK switching to digital TV? And why can’t mobile operators make their mobile internet services better and faster?

A key part of the answer to both is one word: spectrum. Even among my Which? Tech colleagues, the word ‘spectrum’ elicits blank looks. So what is it, and why is it so important? As someone who’s struggled to get to grips with it for years, I’ll try to explain.

On the airwaves

It might sound like geek speak, but spectrum is the virtual life-blood of all UK wireless services. Without it, many services we take for granted – mobile phone conversations, for example – wouldn’t be possible.

Simply put, spectrum is the airwaves that carry information from one place (say a mobile phone mast) to another (say your mobile).

You might think that the apparently boundless airwaves have unlimited capacity, unlike the physical wires of traditional broadband. Hence questions around why mobile operators can’t just make their mobile internet better. But it’s unfortunately not that simple.

Turn up the frequency

Spectrum comes in many different frequencies. Some are better than others at delivering particular types of service. Lower frequencies travel much further than higher frequencies but can’t carry as much information. The most in-demand spectrum frequencies for digital consumer services are somewhere in the middle range.

Each spectrum frequency, like physical wires, has limited capacity. As our demands on this increase, you’ll get jams. Hence the poor reputation mobile broadband has for speed and reliability, particularly for data-heavy things like watching online video.

Of course, coverage and quality aren’t just about spectrum – company investment in transmitters and masts is also vital – but without the right spectrum, no number of transmitters and masts will suffice.

Spectrum and the switchover

Come 2012 the whole UK will have switched over from analogue to digital TV. Not everyone’s happy with this, but it does bring an important positive. Digital TV uses far fewer airwaves than analogue, so the switchover is freeing up swathes of spectrum.

Firstly, this means that all UK residents will have access to Freeview  (bar a tiny percentage). And secondly, the freed-up spectrum can be used to improve mobile broadband services.

This is why Ofcom is auctioning off two frequencies – 800MHz and 2.6GHz for the geeks among you. The 800MHz was freed up by the digital switchover. The 800MHz combined with the 2.6GHz frequency has the potential to bring fast, 4G mobile broadband services to 95% of us.

So that’s spectrum in a nutshell. Everything crystal clear?


There’s still many fingers wrapped in burn dressing in the Mobile industry. There won’t be any hedonistic bidding at this auction.