Atheros and how to convert RSSI to dBm

[Miroslav Chlastak]

Hello,

   is there a way how to convert RSSI from output of "ifconfig ath0 list 
sta" to dBm?:

[snip]

ADDR               AID CHAN RATE RSSI IDLE  TXSEQ  RXSEQ CAPS FLAG
00:4f:62:1d:d8:5d   14    9  11M 18.5    0  15932  22400 ES   A

[snip]

I my test enviroment I use this function:
noise floor + RSSI*2 = signal of client in dBm

Then i get the same value as from "tcpdump -n -i ath0 -p -y 
IEEE802_11_RADIO":

[snip]

10:41:04.746395 86402611933us tsft short preamble 58.5 Mb/s -61dB signal 
-98dB noise antenna 1 [0x00000012] IP 10.0.0.1.2049 > 192.168.100.2.123: 
NTPv3, Client, length 48

[snip]


Right? Or is this conversion "stupid"? Some better idea?

Is there a way how to get noise floor via "ifconfig"? I get it from 
output of "athstats" :(


-- 
Mira