Re: [Discuss-gnuradio] GNURadio FFT Plot and UBX Maximum Input Power

[Marcus Müller]

Dear Ali,

as you've noticed, the dB scale in digital samples just means "relative
to an arbitrary value", and not "relative to a milliwatt". I think
we've talked about that before?

So, in any reasonably constructed signal chain, distortion would start
to appear close to 0 dB Full-ADC-Scale. So all this is alright.

Best regards,
Marcus

On Thu, 2018-01-11 at 13:51 +0300, Ali wrote:
> Hi to all,
> 
> I have an X310 USRP and a UBX-160 on it. There is also an antenna
> connected. I am transmistting some signal by a handheld radio and
> plotting the FFT plot of IQ data in GNURadio. It seems that power
> reaches almost 0dB. If I close too much the spectrum fluctuates, it
> does not look good. I think it saturates.
> 
> When the peak at FFT Plot is -10 or -20 dB, the spectrum's shape is
> good. But the UBX is said to have max. input power of -15dBm which
> -45 dB. Do I give harm to my daughterboard in this case? I am
> confused. It does not look that I am harming.
> 
> Best,
> Ali
> 
> 
> 
> 
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