The other information that's relevant is that we have a range extender to boost WIFI in our offices (previously our children's bedrooms). We usually connect via cable here - but phones and tablets obviously don't.
So when we use InSSIDer we see our two signals. but even with the new router we still get periodic drops (although less severe) in the signal - although mainly from the extender. Even with the old one the two drops kin the two signals weren't always "synchronised" as I expected - now almost not at all. The drops don't seem to affect our connections noticeably - so I assume this is normal? But I have no idea so would appreciate an opinion from someone with more skills than me (which is probably everyone here).
The other question is over channels. Our new router doesn't go above 9 - yet InSSIDer shows us using channels 11+7. I thought we chose channel 6 - I now see when I look again at the router via our browser it's on Auto and says current 11 (interference severe). There is another device in the area showing 11+7 - but it's less strong than the next door signal. Again any info to help us understand what is happening would be appreciated.