On 2.4 GHz there's only three channels that do not overlap: 1, 6 and 11. using any other channel is almost guaranteed to get interference from a different access point unless you are completely somewhere with no competing access points. I know sitting in my family room using a scanner on my laptop there's over two dozen different access points with a fair or better signal strength. Even accounting for six of them being my own (which I separate channels used manually) there's plenty of chances for interference. Also, on 2.4 GHz Roku devices cannot use channels 12, 13 or 14, so the channel should be set manually to one of the three clear spacing channels (1, 6, or 11).
WiFi speeds vary greatly by frequency (2.4 or 5 GHz) as well as distance from the access point, any structure blocking the signal, and the Roku device itself. My Ultra 4800 is less than three feet away from one of my access points. The maximum speed this device reports is about 225 Mbps, which appears to be a hardware limit of the Roku itself based on playing test files from a USB drive. My Express 4k+ is in a different part of the house, again maybe four feet from the closest access point, and it only returns about 125 Mbps. Since it doesn't have a USB connector for playing my test files, I can't verify if that's a hardware limit to the device or simply not as good of a WiFi signal as my Ultra gets.
Dan
Roku Community Streaming Expert
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