Setting txpower above the power of your card

Jason Boxman jasonb at
Sun Oct 20 16:47:07 EDT 2002

On Sunday 20 October 2002 10:03 am, Scott Stapleton wrote:
> Hi,
> After setting hostap up, I noticed the default txpower from my card was
> 4dbm ( 2.5mW ). I procedded to set my card to 20dbm ( 100mW ), as this
> is what it outputs ( WL200 ). I noticed the NS graph on my lappy shoot
> up, as expected.
> I then thought I'd try setting it to 150mW to see what happened. I never
> expected it to increase, but it did somewhat. I then proceded to try
> 30mW, then 100mW again. The signal did not increase this time after I
> changed from 30mW to 100mW.

I had a similiar experience with my LinkSys (pre BroadCom chipset) card.  I 
can change the txpower to its max, 32mW, and my signal quality increases on 
my laptop, but then I can change it to anything from 1, to 31mW and there is 
no decrease in signal quality.  It's very odd.  It's like the initial 
increase just maxes the card (or increases it noticably) and then thereafter 
no further modifications are acknowledged.

> Is it possible to overpower these cards? I have not used the card a lot
> since, but it still seems to be working. I only left it at the 150mW for
> 30 sec's max.
> Is it possible I have damaged the card.

I've wondered about that myself.

> A friend did a similar thing previously and left the power set higher
> for a much longer period ( days even ). His card is a Dlink running
> HostAP and the box now dies and a reset is needed to get it working
> again.

I had that happen with the HostAP release immediately before 2002-10-12.  I 
forget I did, it mightly been playing with the power, but I had to turn the 
box off and on a couple times.  The card simply refused to work.  I went back 
to the May release, nothing, then finally it started working again an hour 
later.  I can't explain what had happened.  At the time, the cards seemed 
partially fried, but it's working 100% since it came back to me.

> Whats the chance of damage and if it is possible, why is it allowed,
> either by the card or driver?
> Regards,
> Scott


Jason Boxman
Administrator TrekWeb.COM - Linux Pages

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