Re: [Discuss-gnuradio] Maximum value of samples

[Sebastiaan Heunis]

Don

> In fact, at
> 10dBm input and 20dB PGA gain I expect your ADC is clipping.  Have you
> looked at a plot of your recieved waveform?

I agree with you on this.  According to the ADC datasheet, we need a
2Vp-p signal at the ADC to utilise the full dynamic range.  One of the
graphs on the datasheet also shows that the input impedance of the
ADC, when the input signal is between 20MHz and 60MHz, varies between
220 and 230 ohms.

This means that anything above around 7dBm should cause the signal to
get clipped.  With input=10dBm and PGA gain = 20dB, I captured a
signal and plotted it in Matlab.  It's just a normal sine wave with
its peak around 8600.  No clipping, which is surely wrong?

I just need to figure out how efficiently the TVRx uses the dynamic
range of the ADC, so I want to compare the maximum sample value that I
get using the TVRx with the maximum possible sample value.

Thanks for the help.

Sebastiaan