The Wi-Fi channel nobody changed: why the line chokes at 8pm, and the thirty-second fix

The evening slowdown has a physical explanation that no speed-test company will spell out: the 2.4GHz band is a single shared room. Your router, the bar across the road, and six neighbours' boxes all talk in it at once, and a microwave runs its own loud broadcast on the same frequencies. When the street gets home, airtime gets rationed - and the one free remedy is the channel number nobody has ever changed on the box.

The map, in the order it matters

• There are three roads, not thirteen: the channel list (1-11 or 13) is an illusion - each channel's signal is wide enough that adjacent ones overlap. The non-overlapping set is 1, 6 and 11. Two neighbours on 1 and 4 are both on the same road; 1 and 11 are not.
• Width is the other half: a 40MHz-wide 2.4GHz signal is double the road space - which on a congested street means double the collision chance for no real gain. 20MHz on 2.4 is the tuned setting; the wide channels belong to 5GHz, where there are many more non-overlapping roads and far fewer boxes using them.
• 'Auto' is a snapshot, not a habit: most routers pick a channel at boot and then keep it for months even as the street changes around them - which is exactly how a box that was smart at 3am becomes the router on the same channel as the new hotspot at the corner. A manual pick, re-checked a few times a year, beats the setting most homes actually own.

The thirty seconds, done as the pros do it

A free Wi-Fi analyzer app on the phone is the whole toolkit: stand at the flat's own wall, not the window, and read the neighbourhood - every SSID, its channel, its signal strength. The rule is not "choose the quietest channel number" - it is choose the channel with the fewest loud signals, and if 1 is empty but the corner shop's box sits next door at full power on it, 11 with one medium neighbour may carry better. Enter the pick in the wireless settings on the router page (the same login as the password change), set 2.4GHz width to 20MHz, reboot, and re-run the analyzer at 9pm to confirm your live choice. Then move the devices that can carry 5GHz onto it - phones, laptops, the console - because the band's shorter range is an honest cost for its real gift: your street is almost certainly not congesting it.

The honest ceiling

Channel changes redistribute the fight; they do not end it when the whole street is loud - a building where nine boxes stack on three roads will still see evening teeth, and that is the physics behind the mesh-with-wired-backhaul and ISP-upgrade conversations, not router-brand advertising. And one router setting that quietly worsens everything under load: QoS turned on with a fake or guessed bandwidth number throttles the line on a lie - if you don't know your real profile, leave QoS off. The free 80 percent of this fix is the channel, the width and the 5GHz nudge; the rest is a bigger pipe or a cable, said with no apologies to either side.