REW Beta Release Question about RTA

[maverikc]

Good morning. I have a question about the data displayed by the RTA "Show distortion" window. Using the generator I produced a 1Khz and -80 dbV signal which I sent to RTA.
The "Show distotion" window, the cursor and the value displayed in RTA practically all coincide at -80dbV.

Then I generated a 1kHZ but -120dbV signal. The cursor and the value displayed in RTA practically coincide (-119.7dbV) but the "Show distortion" window provides a completely different value (-111.16 dbV).

Where am I wrong? Thank you all

 

[John Mulcahy]

The fundamental level is based on power within a 1 octave span, per the AES-17 standard notch filter definition. When the fundamental approaches the noise floor the overall level within that span will be raised by the noise floor. You could use coherent averaging to lower the noise floor.

 

[maverikc]

Thank you John

 

[John Mulcahy]

I'll add a distortion setting in the next build to choose whether to use the AES17-2015 standard notch, it would be better not used when the fundamental is very low.

 

[maverikc]

I'll add a distortion setting in the next build to choose whether to use the AES17-2015 standard notch, it would be better not used when the fundamental is very low.

Very good. Thanks