Re: [Discuss-gnuradio] wx_fft_sink block

Hello Abhilash,

That is because the power level is relative. Unless you use a absolute power level (dBm/Hz, etc), the comparison of the power level magnitude is meaningless. The spectrum analyzer is probably giving you dB'm' readings, but the USRP is not.

You cannot get absolute power level readings from USRPs unless you calibrate them amplitude-wise (by yourself). Even then, USRP is not a perfect replacement of a spectrum analyzer (generally better than cheaper SDRs, though).

Regards,

Kyeong Su Shin

On Fri, Feb 2, 2018 at 2:39 PM, abhilash b <abhilash2606@gmail.com> wrote:

Hello,

I am using USRP N210 with CBX daughter board.

In the GNU radio I use USRP_source block followed by wx_gui_fft sink block. I input a power of -60dB to the USRP.  The input power is measured using a spectrum analyzer.

The RF gain in the source block is kept at 0 dB, sample rate of 25 MHz and center freq of 2.4 GHz

But the fft block shows the power to be -40dB. 

Could you please tell me why such a huge offset.

--

-Regards
Abhilash B

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