No interference for years until now.

I think I am having problems with interference, though I am not certain there aren't other factors involved.

Until recently I had not much more involvement with wi-fi (802.11) than watching the various laptops and other wifi appliances in the household connect automatically. But more recently I had problems and started to delve and it has left me with some unanswered (possibly unanswerable questions). I am a real newbie, but I am beginning to learn some stuff, so please forgive me.

My router (thomson TG585v7) has been on auto channel selection for like years and worked fine. Recently found no devices (except plc ethernet (homeplug)) could connect. Raised a ticket with the isp who said select channel manually. I install insside 2.0 take a look at the channels and found I was sharing the channel with quite a few APs, so I selected channel 4 that no one (as far as I can see) was on and all was well again. After a few days again no one can connect, so I take a look in insside 2.0 and it shows my AP only appears for a few seconds every couple of minutes, but still no one on channel 4. I raise another ticket with isp and they say it'll be interference from non-802.11 products. So I switch to channel 13 (no APs on that either) and all is well again.

Here are my questions.

1. If I could use software, look and see which channels were free and pick one manually and solve the issue (at least in the first problem event) then why can't auto channel selection do that for me. Or even know that noone can connect due to other interference and switch channel automatically. This is after being on auto for years with trouble free wifi.

2. Can I get any free software that may give a rough indication which channels have non-802.11 interference.

3. Nothing new has been brought into our house and nothing has changed operational state. What could a neighbour have possibly turned on that would completely kill off channel 4 on to all intents and purposes a permanent basis. No improvement for days. No pockets of normal connectivity. This is after years of trouble free wifi.

4. What other advice can any one give, eg my router is b/g maybe get 11n? try to avoid overlapping channels? What are they? Etc.....

Any help or advice for this newbie greatly appreciated.

no. the radios in wifi gear are channelized and designed to receive specific kinds of modulation. there is no way to manipulate them to behave like a spectrum analyzer

a wireless video camera

inSSIDer will tell you what channels are in use. It's not terribly bright, and only seems to show channels that are broadcasting a SSID. Using this can tell you what channels are present in your area.

Another possiblity is that the radio chip on your wifi is cooking itself. They have only a finite lifespan. This can be checked by borrowing someone else's AP, and seeing if it makes a difference.

Check for location changes. If you get less interference when the laptop is close to the AP, it is more likely to be interference. If it's no better close than it is at the otehr en of the hosue, then the AP may be dying.

Power supplies are also a suspect. A power supply usually has capacitors in it that level out the AC to DC (oversimplifcation.) The can leak as they get older, and the result is that you get DC that has a bit of AC ripple on it. This can interfere with the function of the AP.

If you can find a compatible power supply (same plug, same voltage, same or somewhat higher current capability) you can try that. Given the lack of standards, this is problematic, but Radio Shack does sell some universal wall warts that cover most of the common situations.