...but I don't know what it can be.
I sought advice in here about a month ago about a poor signal from my SMC barricade running 802.11b and was pointed in the direction of NetStumbler, which showed a non-constant signal/noise ratio (the display on NetStumbler for my network looked like a comb compared to the two other WLAN signals in my area which were nice steady green blocks).
I've now replaced the SMC Barricade with a Belkin Pre-N 802.11g router, and whilst the network signal is stronger than before, the diagram in NetStumber still resembles a comb.
I've changed channels to see if the signal improves on both the old and WLAN routers but there is no noticeable improvement. The other WLANs I can pick up emit a consistent signal whereas mine doesn't - even when in the same room.
It's not the cordless phone and I don't have a microwave. The router's position is on the top of a shelf unit.
Any other ideas or suggestions gratefully received.