Re: [Discuss-gnuradio] Changing Bandwidth USRP

[Marcus Müller]

This is a completely different problem, is it? Bandwidth is orthogonal to the 
concept of dynamic range and amplitude values.

Anyway, your FFT plot knows about complex samples; therefore, it displays dB relative to 
the numeric value of "1.0"; this has nothing to do with your input signal 
power. But since USRP/daughterboards tend to work linearly over most of their available 
power range, you can just add a multiply_const to your signal processing flowgraph and 
get your value.
The factor, however, depends on your ADC/daughterboard combination, on the gain you set 
for the RF frontend, a little bit on temperature, the tuner, the impedance matching of 
your RF input to the Daughterboard etc.  So if you already know what you're putting in, 
just use this as a reference and "calibrate" yourself.

Hope that helped clear things up,

Marcus

On 10/04/2013 01:05 PM, Antmrt wrote:
> Thanks Marcus, my problem is how to calibrate the scale on the FFT plot. e.g:
> I'm feeding a signal of -30 dBm to the usrp and on the plot the value
> becomes about -10 dBm
>
>
>
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