Speed variations - noise margin?

[locky]

Thanks for all suggestions. Changed channel to 11. No other networks seem to appear/disappear.

I will monitor speeds over next few days.

Would upgrading to a wireless n card make any significant improvements?

Is a draft n spec card OK to use with the router which I assume is not draft n spec?

[Isitme]

You would benefit from upgrading to an N standard card. A draft N may work, but there is no guarantee. Manufacturers supplied what was termed 'Draft' devices before the N standard was finally ratified. Each manufacturer had different ideas so they are not necessarily compatible with the full N standard. If you are getting the Draft N card free, it is worth trying it, buy I would not recommend buying one. If your Lappy has a Mini PCI connector then one of these would be fine -
[ame=http://www.amazon.co.uk/gp/product/B0017YHYFM/ref=pd_lpo_k2_dp_sr_3?pf_rd_p=103612307&pf_rd_s=lp o-top-stripe&pf_rd_t=201&pf_rd_i=B00194XKXA&pf_rd_m=A3P5 ROKL5A1OLE&pf_rd_r=0DCGJVCZXSTPZTY35VAB]TP-Link TL-WN861N Wireless N Mini PCI Adapter: Amazon.co.uk: Computers & Accessories[/ame]

The USB version is only a tenner -
[ame=http://www.amazon.co.uk/TP-Link-TL-WN821N-Wireless-USB-Adapter/dp/B00194XKXA]TP-Link TL-WN821N Wireless N USB Adapter: Amazon.co.uk: Computers & Accessories[/ame]