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Re: [Discuss-gnuradio] Question about the FFT

From: Kóczián Gergely
Subject: Re: [Discuss-gnuradio] Question about the FFT
Date: Fri, 23 Oct 2009 07:21:06 +0000


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

Attached picture:


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

Kóczián Gergely
Neptun kód: XCK220
Telefon: 06-70-637-19-85
skype: koczian.gergely
Műszertechnikai és automatizálási intézet
Automata gyártórendszere modul - F4

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