We’ve written many times about how crowded the 2.4GHz frequency band is becoming these days, and how that can affect the reliability and speed of your wireless network.

There are so many devices and routers now using the unlicensed space between 2,400MHz and 2,475MHz that finding a quiet, undisturbed channel for your network to reside on is nigh on impossible. That’s why we recommend anyone upgrading their wireless router chooses a dual-band model — one that gives you the option of connecting in the less congested 5GHz frequency band.

This can be a difficult concept to grasp without visual aids, so let me show you exactly what we mean when we talk about RF congestion.

Using our recently-acquired Wi-Spy spectrum analyser (kindly supplied by Metageek for use in a forthcoming wireless router Labs), combined with the firm’s Chanalyzer 4 radio frequency (RF) analysis software, we recorded the above graph.

It shows all the RF activity in the vicinity of the PC Pro office, and can detect not only nearby wireless networks – of which there are an alarming number — but also other devices using the 2.4GHz band.

Look closely and you’ll see that, on channel 8, there’s a non-Wi-Fi source of interference, represented as three bright stripes in the bottom “waterfall” window: I’ve not tracked down the culprit yet. To the right, the broad red/green stripe flanked by two narrower vertical green  lines shows you the devastation a cheap wireless video sender can wreak.

While this might seem a rather extreme example, I’m sure that many living in densely populated urban centres will be surrounded by a similar level of congestion and interference. Just imagine how many baby monitors, cordless phones and wireless routers there are in a modern, central London block of flats, and you’ll get the idea.

It’s frequency band bedlam out there, and the effect is slower, more unreliable wireless networks. Now take a look at the 5GHz band at the same location:

The difference is quite staggering — an oasis of calm by comparison, with only PC Pro’s own dual-band wireless router interrupting the tranquil RF landscape.

If that doesn’t get you hankering after a dual-band router, then nothing will.