SR71-A Txpower Question

[Shant Kassardjian]

Hello Adrian,

Glad to see you're always there for us! 

I spent countless hours looking for ubiquiti documentation that proves setting txpower 0 turns off the device... 

and found nothing so far. Either way, I still see this as a useful feature to consider :) 

Thanks for the detailed explanation regarding the txpower formula, it makes much more sense now whenever I play with the power transmit settings.

Thanks again!
Shant K

> Date: Wed, 25 May 2011 00:43:21 +0800
> Subject: Re: SR71-A Txpower Question
> From: adrian at freebsd.org
> To: shant at skylab.ca
> CC: freebsd-wireless at freebsd.org
> 
> Hi,
> 
> ifconfig wlan0 txpower 0 merely sets the txpower to 0dBm, which isn't
> "off" strictly speaking. It's actually 1mW.
> 
> The SR-71A also has a TX power offset in hardware. If I remember
> right, the hardware is actually a couple of dBm higher than what you
> configure. So when you configure 19 dBm, you're programming the
> hardware at 19dBm, but the hardware responds by allowing a max of
> 16dBm per channel, which is * 3 (3 TX chains, as per the patch I gave
> you) to give ~ 21dBm. I'd have to check the math to get the exact tx
> power offset but that's roughly what's going on.
> 
> Now, if it's documented somewhere that 0 dBm should be "killing" the
> interface, let me know. :)
> 
> 
> 
> Adrian
> 
> On 25 May 2011 00:24, Shant Kassardjian <shant at skylab.ca> wrote:
> >
> > Hello FreeBSD-Wireless,
> >
> > I've been running SR71-A on FreeBSD 8.1 for quite some time now and it's been running very well. Many thanks to Adrian Chadd who really helped ironing out all my questions!
> >
> > My only problem so far that I've noticed is that when I do:  ifconfig wlan0 txpower 0; this does not turn off power to the wireless as it's suppose to and rather I have to bring down the interface manually to shut it down hence whenever I need to start it up again I have to reconfigure the interface.
> >
> > >From my observation it looks like changing the txpower rate using ifconfig has little to no effect controlling this adapter.
> >
> >
> > My question is that, could it be because I have compiled the kernel with the following modifications as suggested by Adrian Chadd to take advantage of Max 3x antenna transmit power that I am having this problem?
> >
> > Edit sys/dev/ath/ath_hal/ar5416/ar5416.h:
> >
> > #define AR5416_DEFAULT_RXCHAINMASK      7
> > #define AR5416_DEFAULT_TXCHAINMASK      7
> >
> >
> > Does anyone else have this symptom with their SR71-A (AR5416)?
> >
> >
> > Many thanks in advance;
> >
> > Regards,
> > Shant K.
> >                                          _______________________________________________
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