Hi List,

I am trying to find the spectrum symmetry of a modulated signal.

That’s why i use the fft block on GRC. (The flow i used is attached).I

use AM modulation as an example. And i write a block that finds the

left and right side of the spectrum and make the calculation

P = (PL - PU)/(PL+PU).

But every time i run the flow the point of the carrier is changing. I

use 2048 point fft, hence i expect to find a carrier at the 1024th

point and every 2048 point after (3072, 5120, etc) until i stop the

flow.

But this value changes any time i run the code( some values i take as

an ex: 1010, 1012, 1018, 999, 1045, 1044, etc). I also attached the

code for the calculation. I couldn’t figure out what i did wrong.

Thanks for any help.

Mehmet.