Re: [Discuss-gnuradio] Question about the FFT

[Kóczián Gergely]

Hello!

Thanks for the help. Now the frequency is correct. But the amplitudo
is wrong. I messauring in the real life a triangle signal and it's not
similar.

Attached picture:

http://img7.imageshack.us/img7/8049/messung9.png

The second peak have to be:

                                           Frequency: 3kHz
                                           Amplitudo: -45dB

The amplitudo of the first peak also not correct.

Best regreads

2009/10/22 Josh Blum <address@hidden>:
>
>
> Kóczián Gergely wrote:
>>
>> Hi all!
>>
>> A have a little probleme with FFT.
>>
>> I use the GRC without USRP. I would like to messeaure a triangle
>> signal, but i never becam the right effect. I attached the picture
>> about the measuring.
>>
>> The problem are the followed:
>>
>> I don't why but, i have allways a peak at 0Hz. - Independent from the
>> type of signal
>
> The imaginary part of your signal has a dc offset.
>
>> On the picture i messaure a triangle, but the next peak in the FFT
>> failed at 12kHz.
>>
>
> Try making it a real signal (float outputs, not complex outputs).
>
>> Attached picture:
>> http://img8.imageshack.us/img8/5620/messung5.png
>>
>> Have you any Idea?
>>
>> Thank: Gergely
>>
>>
>> _______________________________________________
>> Discuss-gnuradio mailing list
>> address@hidden
>> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>



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