WiFi routers will hop to less congested channels automatically these days; the odds that your neighbourhood has lots of WiFi base stations you can see, but there is still a frequency that's almost entirely free is _very_ low.
There are effectively three 2.4 GHz channels and about six 5 GHz channels, but because the range of 5 GHz is so much smaller you should be able to find on open 5 GHz channel even in the densest, tech heavy, apartment building.
As the author said in the comment section: "I usually suggest turning 2.4 GHz off altogether so none of your users will ever connect to it by accident."
As for AP's sharing channels, this is great in concept but our (3 unit) building became so overcrowded in the 2.4 GHz spectrum that devices couldn't connect which caused people to add more routers and repeaters to "boost" the signal making it even worse. If you can't connect, you can't share.
You are correct. Most router these days select channels automatically.
But the automatic channel selection is not very accurate in my personal observation as well as that of a few others on the internet [1]. Wish it were better though. I feel that there are numerous problems in automating the channel selection
1. We have to make sure that this happens without any downtime otherwise there is poor QOS. If the router has to reboot to choose a channel you're out of internet for about 5-10 minutes. It can be very frustrating if it happens often.
2. As if that was not enough you have to draw extra power to scan nearby access points and constantly react to the changing signals. (This would also defeat the point of using low power signals)
In my opinion it is better to tune the routers manually than to set it on automatic channel selection.
> the odds that your [...] is _very_ low
Yes unfortunately that is true. There is little we can do about it. But there is one redeeming factor. As per my understanding interference depends not only on the base access point but also on the client. In other words the channels will deteriorate if the communication link that is the pairing of client with the access point interferes with the signals of another access point.
On low ranges you can create mini line of sight networks that will happily co exist with any number of signals. Example wifi on laptop working with bluetooth mouse.
[Router] --------- [laptop]
|
|
[mouse]
It is not such a good example because signals at such a small distance are strong enough to overcome any interference but the principle stands in other conditions as well.
