Atheros wireless card keeps losing signal when signal is too weak

[Sam Leffler]

Paul B. Mahol wrote:
> On 3/25/09, Yuri <yuri at rawbw.com> wrote:
>   
>> I have Linux box sitting next to FreeBSD box that has a very cheap
>> Airlink 101 card but it has no problems connecting to my WiFi network.
>>
>> Every time when Linux box says that quality of connection drops below
>> 10/100 FreeBSD box shows "status: no carrier".
>> Linux connections still function ok.
>>
>> I even bought a large WiFi antenna for FreeBSD box but still have this
>> problem.
>>
>> Is there some 'sensitivity' parameter that driver may be setting too low
>> on the card?
>>     
>
> I'm only aware of roam:rssi & roam:rate
>
>   

Those parameters control the roaming algorithm.  The OP didn't identify 
their card, freebsd version, or provide any info about their setup or 
why ifconfig reports "no carrier".  It just sounds like there's a loss 
in the signal and freebsd gets a beacon miss and tries to reconnect 
while linux does not.  Once the rssi drops to "10" (presumably 5dBm) 
minor variations in the environment can become significant (e.g. 
orientation of a laptop, obstructions, antenna quality) and it's 
impossible to comment on what's happening w/o detailed information such 
as provided by athstats.

FWIW cardbus cards that follow the reference design closely typically 
work pretty well and don't benefit from an external antenna.  Vendors of 
cheap designs often scrimp when it comes to the antenna.  When wireless 
is inside a case (e.g. a PCI card) then it's worth remoting the antenna 
but you need to be careful about routing the pigtail(s) and I can't 
count the number of times I've tracked problems down to faulty cables 
and/or connections.

    Sam