Why can’t I connect to my office router when it works OK at home?

Q I have recently rented a desk in a shared office, where access to a communal Wifi hotspot is available as part of the deal. However, I seem able to connect to this only sporadically.

Sometimes the connection will work first time and work without problem all day. At other times, though, my laptop refuses to ‘see’ the router.

As this same laptop works perfectly with my wireless router at home, I first thought that perhaps it was the office Wifi equipment – it’s a BT Business Broadband Hub, model number BT2700HGV.

However, other colleagues in this shared office stay connected all the time and never seem to have a problem. I’ve even sat side-by-side with someone using a different laptop and their PC picks up the Wifi signal while mine doesn’t, even when sitting right next to the router.

The laptop runs Windows XP and I use an old USB wireless adapter that was given to me by an American friend who was upgrading (though as I said, I have never had any problems with it at home). Any ideas?
Jim McMahon

A We think the clue that points to the answer is to be found in the last sentence of your email – the wireless adapter given to you by your US pal.

To explain, it is necessary to understand that Wifi signals are broadcast over different channels in the 2.4GHz part of the radio spectrum. There are a total of 14 available channels but, because of differences in the way that bandwidth is allocated by the various authorities around the world, these are not universally available in all countries.

In the UK, for example, it is illegal to use channel 14; though this band is allowed in Japan. More to the point, in America, only channels one through to 11 are sanctioned for most Wifi equipment (there is a small exception to this rule but this is immaterial for the purposes of our answer).

We are guessing that your second-hand wireless adapter was, at the point of manufacture, hardware-limited to meet the Wifi requirements of the US market. In other words, we think that your American wireless adapter is able to send and receive signals on Wifi channel numbers up to and including 11.

This is relevant because, in common with many routers sold in the UK, the BT2700HGV is capable of broadcasting over Wifi channels one to 13. In addition, this router’s default channel setting is ‘Auto’, which means that the router is free to chop and change the channel it uses (probably based on an algorithm that detects the channels used by other nearby routers to combat wireless congestion).

Regardless, when the router decides that channel 12 or 13 is the best one to use, your wireless adapter will no longer be able to detect the signal – a theory that fits with the described symptoms.

There are a few things that can be done to resolve the problem. If you or the person letting the desk to you has access to the router’s password, then use a web browser to log in to the administration screen and fix the channel number at 11 or below.

Alternatively, it is possible that your wireless adapter’s settings can be tweaked to allow it to communicate on channels 12 and 13. As you told us nothing else about the device we can’t offer precise instructions but, in XP, click Start followed by Control Panel.

Now click the Performance and Maintenance link followed by System. In the System Properties window, click on the Hardware tab followed by the Device Manager button. Click to expand the Network adapters section then right-click the entry for your wireless adapter and choose Properties.

Click the Advanced tab then explore the list under the Property heading: if you see an entry labelled ‘Channel’ or ‘WZC IBSS’ click it to see if there’s an option available for channel list or country.

Finally, if all else fails buy a new wireless adapter: they are pretty affordable these days and any model bought in the UK should be able to communicate on all 13 legal Wifi channels.