Global txpower in ath

Sam Pierson samuel.pierson at
Tue Aug 23 15:59:32 GMT 2005

On 8/10/05, Sam Leffler <sam at> wrote:
> Sam Pierson wrote:
> > I noticed that when I control the signal strength through
> > ifconfig, I can effectively reduce the signal when I set it
> > as something like:  ifconfig ath0 txpower 1.  I have read
> > that this input is device driver dependent and I couldn't
> > find anything in the interface that handles txcontrol.  Are
> > these values taken in exactly or are they rounded to some
> > less fine-grained control number?  Thanks,
> The current support has a limited number of settings for the tx power.
> I don't recall how many there are but it's chip dependent and possibly
> also frequency-specific.  5212 parts are capable of controlling txpower
> on a per-packet basis but getting it "right" has proven very hard and is
> not yet supported.
>         Sam
I read that the Atheros chipset supports up to 60 different txpower
options and like you said, it seems to be limited, to about 45 different
settings at this point (ie: only txpower 1-45 are respected).  The thing
that has been bothering me is that the card is supposed to be capable
of transmitting at like -90dBm (practically nothing, only good for 
communication at a few meters with normal wireless cards) and at
its lowest power setting, transmits like a -50 or -60 dBm signal. This
ends up going like 60m before any significant signal loss.  Are there
_any_ cards at this point which support a global variable rate txpower
and can transmit a signal only good for a few meters?  Or is the support
for these cards just not at that point yet?  Even the cisco cards that I
tried, which can supposedly transmit at 101 different levels, send like
a -60dBm signal at its weakest strength.


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