Hi @stephenw10
Thanks so much for replying. My initial poor understanding was that the Atheros chip in the Qotom was an AR9382, which information I got from the Aliexpress website, but of course I should have realised that while great on price and shipping and products, technical details from vendors there are very often wrong or missing.
Using dmesg I find that it is actually an Atheros AR9285. From the Atheros datasheet:
Frequency Band 2.4 GHz
Network Standard 802.11b, 802.11g, 802.11n
And ifconfig confirms:
[2.4.5-RELEASE][admin@pfsense.localdomain]/root: ifconfig ath0_wlan0 list channels
Channel   1 : 2412  MHz 11g ht       Channel   7 : 2442  MHz 11g ht       
Channel   2 : 2417  MHz 11g ht       Channel   8 : 2447  MHz 11g ht       
Channel   3 : 2422  MHz 11g ht       Channel   9 : 2452  MHz 11g ht       
Channel   4 : 2427  MHz 11g ht       Channel  10 : 2457  MHz 11g ht       
Channel   5 : 2432  MHz 11g ht       Channel  11 : 2462  MHz 11g ht       
Channel   6 : 2437  MHz 11g ht
[I am so ignorant I never knew ifconfig could list the channels. I ought to read the manpages more carefully!]
So the puzzle is resolved, and thank you.
The next question is, does anybody know if there are appropriate 5Ghz cards for the Qotom Q355G4? It's just standard PCIe is it not?