[Discuss-gnuradio] FFT bin ordering

[Dirk Gorissen]

Hi All,

This should be a simple question. I have the following:

sdr -> decimation/filters -> stream to vector -> FFT -> complex to
mag2 -> log10 -> python block - > ...

The FFT block is configured as:
type: complex
Direction: Forward
Shift: yes
length: equal to input vector length

The python block should be trivial in that it just snips out a subset
of the FFT bins (around the center frequency).

My assumption was that the center frequency is at the middle bin
(Shift = True) and that if I want +/- 500Hz (for example) I can just
take the bins (middle bin index - 500) -> (middle bin index + 500)

However that does not seem correct. Perhaps there is a bug somewhere
else but just wanted to check Im doing the right thing.

Cheers
Dirk