Re: how to auto detect peak frequency in QT FFT sink

Hi Kyle,

many thanks.

i successfullly run fft peak it can get the index of peak but i want the frequency value not only the fft index. it seems it is difficult to use gnuradio block to compute the frequency from fft index because it need to deal with the top half part and the bottom half part of the band. so i think of modify fft peak block. the source code of fft peak block is all python and i don't know how to insert my code. it seems the max fft index connect to a null sink named null_1. how to insert code between the connection? and i also need to pass the center frequency and the frequency band to the block which seems defined in the xml file?

From: Kyle A Logue <kyle.a.logue@aero.org>
Sent: Wednesday, December 2, 2020 12:48 AM
To: james jordan <james.jordan.999@hotmail.com>; discuss-gnuradio@gnu.org <Discuss-gnuradio@gnu.org>
Subject: Re: how to auto detect peak frequency in QT FFT sink

just did a quick test, couldn't be simpler

max_i reports the argmax of the fft, with wrapping

So in the above example:

1 kHz -> 1
5.5 kHz -> 5
-1 kHz -> 31
-8 KHz -> 24

increase from 32 to increase resolution

Kyle

From: james jordan <james.jordan.999@hotmail.com>
Sent: Monday, November 30, 2020 18:37
To: Kyle A Logue <kyle.a.logue@aero.org>; discuss-gnuradio@gnu.org <Discuss-gnuradio@gnu.org>
Subject: Re: how to auto detect peak frequency in QT FFT sink

Hi Kyle,

is there any document for how to use the block in gr-fhss-utils especially for fft peak block. what is the two output of fft peak?

From: Kyle A Logue <kyle.a.logue@aero.org>
Sent: Friday, November 20, 2020 12:26 AM
To: james jordan <james.jordan.999@hotmail.com>; discuss-gnuradio@gnu.org <Discuss-gnuradio@gnu.org>
Subject: Re: how to auto detect peak frequency in QT FFT sink

cmake version is too low so i can not build gr-fhss

gr-fhss has a 3.7 and a 3.8 version if you check the tags on github

how to store max result to a gui label?

qt-number-sink maybe

From: james jordan <james.jordan.999@hotmail.com>
Sent: Wednesday, November 18, 2020 22:07
To: Kyle A Logue <kyle.a.logue@aero.org>; discuss-gnuradio@gnu.org <Discuss-gnuradio@gnu.org>
Subject: Re: how to auto detect peak frequency in QT FFT sink

Hi Kyle,

Thanks. my cmake version is too low so i can not build gr-fhss. i try to use fft->max but how to store max result to a gui label?

From: Kyle A Logue <kyle.a.logue@aero.org>
Sent: Thursday, November 19, 2020 4:05 AM
To: james jordan <james.jordan.999@hotmail.com>; discuss-gnuradio@gnu.org <Discuss-gnuradio@gnu.org>
Subject: Re: how to auto detect peak frequency in QT FFT sink

2 things that come to mind:

stream -> fft -> argmax
in sandia fhss utilities they have an FFT Peak block that does what you want

https://github.com/sandialabs/gr-fhss_utils

Kyle Logue

Senior Engineering Specialist

⚝ The Aerospace Corporation

From: Discuss-gnuradio <discuss-gnuradio-bounces+kyle.a.logue=aero.org@gnu.org> on behalf of james jordan <james.jordan.999@hotmail.com>
Sent: Monday, November 16, 2020 19:09
To: discuss-gnuradio@gnu.org <Discuss-gnuradio@gnu.org>
Subject: how to auto detect peak frequency in QT FFT sink

Hi all,

i want to see the fft of the signal and also want to detect the peak frequency if there is a peak signal.

how to achieve this?

From:	james jordan
Subject:	Re: how to auto detect peak frequency in QT FFT sink
Date:	Thu, 3 Dec 2020 13:50:30 +0000