TP-Link Deco M4 with 3x units is £95 on Amazon UK
Thanks. This recommendation may turn my head. I've thrown it into the mulling pot while doing some more testing.
I moved the powerline ethernet to an outlet near the media system. The added length of copper ring main dropped the data rate from 55Mbps to 42Mbps, but the connection remains solid and the player is happy. AP3 (TL-WDR3600) is now decommisioned.
Coverage of the whole building using RT-AC66U-B1 as main router (AP1) and a wireless AP on floor 3 (AP2) still looks feasible. The biggest challenge remaining is providing good enough guest network to the basement. There is rockwool suspended by chicken wire in the ceiling void as a fire barrier. This attenuates RF more at 5GHz than at 2.4GHz. The basement mains wiring is on the other side of a sub-meter and distribution board, so forget powerline ethernet.
Existing guest network from RT-AC66U-B1 is assigned to 2.4GHz Control Ch1 Wireless Mode: Auto, Bandwidth: 20MHz. The guest network has DTV, work laptop, a couple of mobile phones. This struggles to deliver acceptable performance when videoconferencing. When I tried forcing Wireless N , Bandwidth: 40MHz, performance dropped to the level of unusable dogmess. And that was on floor 1 around 3m from the router. Compare and contrast with 2.4GHz Wireless N from 10yo AP2 delivering >120MBps tested using 9 + 13 and 5 + 9. Further testing is needed to work out why RT-AC66U-B1 is bad in N mode if I am to gain any useful improvement to the basement Wi-Fi.
RF survey of 2.4GHz using inSSIDer indicates most of the neighbours are using either Ch1, Ch6, or Ch11 in 20MHz bandwidth, b/g/n mode, all in region of -80dB to -90dB signal strength. These antagonist networks are using the "US" and legacy 22MHz spaced set of "preferred" 2.4GHz channels. I can see one maverick plonker using Ch3 and another using Ch10. Am I being a plonker to think that here in the UK they should all be using Ch1, Ch5, Ch9, Ch13 and no other channels? Not that I can do anything to change it though. One of the SSIDs is Eduroam, from a nearby UK university campus, on Ch11.
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