raw to dBm conversion

[Dan Williams]

On Tue, 2006-06-27 at 13:20 +0200, Valerio, Danilo wrote:
> Hi everybody,
> I searched in the mailing list archive for information about the 
> conversion from the raw value of Signal and Noise to a dBm value but i 
> didn't find anything really considerable...
> I'm sniffing via TCPdump, and i need to convert that raw values of the 
> prismII header (or AVS header) to dBm values...
> After having a look into the driver code and making some measurement, i 
> realized that a correct formula seems to be:
> 
> ((raw_value) - dBmAdjust) * (100/255) - 100
> 
> With this conversion, the signal strength can be between -90dBm and -40dBm.

That looks pretty good.  Most cards will bottom out around -95dBm or so,
and -40 is a pretty good signal.  Ideally you should be able to get -20
or -30 at least right next to the AP, but this range looks OK.

Dan

> Is this correct? I'm really getting crazy with this stuff :-)
> Please, let me know if you have additional information about it...
> 
> This is my configuration:
> 
> wifi0: NIC: id=0x800c v1.0.0
> wifi0: PRI: id=0x15 v1.1.1
> wifi0: STA: id=0x1f v1.7.4
> 
> 
> Thanks a lot,
> Danilo
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