thanks for the link, I analyzed the Q1-Q4 article
Q1: What are the conditions for an AP to fall back to 20 MHz?
Q2: Is the fallback done on a frame by frame basis or by static mode switch?
Q4: Do non Wi-Fi sources, i.e. Bluetooth, baby monitors, microwaves trigger fallback?
Q5: How do I know if my router will fall back?
I have on this access point running on 40MHz devices, as far as I understand this is not my case
Q3: Does the neighboring network need to be active?
I ran a speedtest on the phone to check
How can I check?
Q1: What are the conditions for an AP to fall back to 20 MHz?
2) A client device with its 40 MHz ("fat channel") intolerant bit set is detected
An example of another cause for fallback is that if an 802.11n station sends a “20/40 BSS Coexistence” management frame containing one “20/40 BSS Intolerant Channel Report” element to AP. If the report includes a channel in its channel list that is within the +/- 40 MHz of its set channel, the AP will fall back to 20 MHz mode.