I tested it last night. My modem is the new T3200M from Telus. My iPhone is 3 ft away from the modem using 5G connection
channel 44: download 33Mbps upload: 22 Mbps
channel 161: download 50Mbps upload: 18 Mbps
Upper channels give stronger signal in close range.
What happens when the clear channels are not showing up in my settings?
These channels are known as DFS channels. These channels are automatically selected by the router because the spectrum that they reside in is shared by radar systems. The T3200M scans the environment and if the channel is being used by a rader, it will automatically either adjust the broadcast power or switch over to a different channel. Since the spectrum is shared, you cannot "select" one channel from the list of DFS channels. You need to let the router choose one for you. Hope this makes sense.