Re: [Discuss-gnuradio] problem about the value of spectrum_sense's power

[Nick Foster]

On Mon, 2011-03-28 at 09:23 +0800, george1012 wrote:
> Hi,all
> i have been studied usrp_spectrum_sense for a while and acquired some 
> achievements of spectrum sensing. But there is still a problem confused 
> me,that is the value of my output power spectrum. i use bluetooth signal
> as my source signal because of its frequency range. i also look up the 
> specification of this bluetooth signal's power, it's about 20dBm. However, my 
> received signal from usrp value is large more than 20dBm,
> it's about 70dBm. i do not know what should i modify from spectrum_sense.py. 
> Is it the gain control cause? i am now in trouble,any help would be 
> appreciate.
> 

The USRP doesn't give you absolute power in dBm, it gives you relative
power in dB. If you want calibrated values, you'll have to use a signal
source with a known power output to obtain a reference level, and
compare your Bluetooth signal to that.

--n

> Regards
> 
> 
> 
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