It is possible to return the wireless radio information using the following command and substituting either "wlan0" or "wlan1" for the 2.4Ghz or 5Hgz radios. Note this command uses the "/cgi-bin/luci/rpc/sys URL
curl --data-binary '{"params": ["iwinfo wlan0 info"], "jsonrpc": "2.0", "id": 1, "method": "exec"}' -H 'content-type: application/json;' https://192.168.1.1/cgi-bin/luci/rpc/sys?auth=<your authorisation token>