@gjmartin 

Hi,

I am unable to answer all of your questions, but I will try to explain some of the "strange" things you've experienced with the 5 GHz band.

In most countries the regulations for the 5 GHz band mandate that before using DFS channels the router must first monitor the channels to be used for the presence of radar signals.

In the "EU" region, for DFS channels 52 to 64 that period is defined as "at least 60 seconds". In the channel range from 100 to 140 it is also 60 seconds for channels not used by weather radar and 10 minutes (not a typo!) for channels that operate on frequencies usually used by weather radar.

My guess is that when you felt like the router never started broadcasting you probably used one of those channels and just hadn't waited long enough.

The channel you select in the router's configuration webpage is the "control channel". If you select a channel width of greater than 20 MHz, then additional adjacent channels will be occupied as well.

Regarding signal strength.

In case your Archer AX72 is an "(EU)" version (check on the label underneath the router), then your observations would make sense.

According to the EU regulations on channels 36 to 64 the transmit power (as emitted by the antennas) must not exceed 200 mW, while on channels 100 to 140 the transmit power must not exceed 1000 mW.

Of course we don't know how much of the permitted power levels the AX72 actually uses, but expect the signal on channels 100 to 140 to be stronger than on channels 36 to 64.

  @woozle 

Yes, I'm in the UK, so using an EU version router.

Thanks for the great explanation of the DFS Channels, I did do some reading up, but it was mostly about events occurring on an already established broadcast, i.e. when an event is detected the router will switch the broadcast to a different channel and then there is the wait time (up to 30 minutes) before it tries to reestablish on the DFS channel.

What you now say makes sense on why it was taking so long to see any broadcast on some channels. Ch 140 is obviously not used for Weather, as that channel comes up quite quickly, and gives me better coverage in the worst room in the house. And with the details on the transmit power, that also makes sense, in the worst room using lower channels I'm getting roughly RSSI -87 on 5GHz, switching to CH 140 that goes to -62, and becomes more stable.

I may investigate a Mesh or OneMesh type system, as I have a hard-wired point that I could use as an Ethernet Backhaul to provide extra coverage in the weaker parts of the house.