Re: [Discuss-gnuradio] GRC FFT Plot

[madengr]

I misread you question and thought you were receiving with the USRP.  Same
procedure, just don't let the transmitted signal go past +/- 1.0 or you will
clip the DAC.  In practice keep it backed off 6 dB or more to allow for
crest factor.

Lou
  


madengr wrote
> 1) Send in a CW tone from a signal generator of known power (dBm)
> 2) Read the level from GR FFT (dB)
> 3) Figure out the amount you need to offset (dB) 
> 4) Multiply your samples by a constant value of 10**(offset_dB/20.0)
> 5) The GR FFT will now be calibrated to an absolute power (dBm).
> 
> Note if you change any settings, technically you would have to go through
> this again.
> 
> Lou
> 
>  
> Jan wrote
>> Hi guys,
>> 
>> I transmitted this -30 dB signal (Image 1) using a usrp: The spectrum
>> analyzer displays -50 dBm (Image 2) as its reading. My receiver end
>> picked
>> up the signal with the same peak power at -30 dB (Image 3). I'm confused.
>> How
>> do I convert the dB power in the GRC to the received signal of the
>> spectrum
>> analyzer in dBm? How do I convert the Power (dB) of the FFT to dBW or
>> dBm?
>> 
>> Best,
>> 
>> *Gerome Jan M. Llames *





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