The latency is also massively better -- I surgically implanted an "ancient" ath9k into my laptop and 5ghz wifi latencies dropped 6x compared to the "modern" broadcom chip on the laptop's motherboard. Still getting 300mbit/sec.
All it cost me was the left speaker, removed to make space for the superior wifi card with open-source firmware.
There are a bunch of these 5ghz ath9k USB sticks, all of which are basically the same ar7010/ar9280 reference design from atheros with different plastic housings around them.
Only if either (a) both networks use the same channel or (b) the networks use different bands (i.e. one is 5ghz and the other is 2.4ghz).
In order to scan usefully you need to listen on more than one channel from each band. Hence, the interruptions.
I suppose in theory if you were using a 5ghz network you could scan all the 2.4ghz frequencies. In practice there is little demand for this, so the proprietary firmwares don't support it (at least some, and often all, of the scan routine happens in firmware).
This is really interesting so I did an experiment.
I connected my iPhone to a 5 GHz-only network on channel 36, and my MacBook Pro to a 5 GHz-only network on channel 48, and I could still AirDrop between them at 300 MBit (which exceeds any real-world speed I've seen on 2.4 GHz), and both devices retained connectivity (an iperf on the MacBook dropped from 600 Mbit to 300 Mbit while the AirDrop was in progress)
After messing around with this and sending around 10 AirDrops, now the feature is completely broken no matter what I do (same network, etc) so who knows (lol)
https://github.com/qca/open-ath9k-htc-firmware