Re: [Discuss-gnuradio] Why is fft output complex?
On 10/11/2014 05:38 PM, k1...@comcast.net wrote: I can't wrap my head around why fft transform of complex signal produces a complex output. After all the output reflects the amount of energy per frequency bin and frequency bins and energy are both real numbers, no? I'm trying to write a python script to analyze the energy across frequency bins but I don't know where to insert a complex to mag block. I think if I can understand the fft I will know to put the complex to mag. The output of an FFT is complex because it contains magnitude _and_ phase. If the output is I,Q (cartesian coordinates) then the magnitude is the length of the vector from 0,0 to I,Q or sqrt(i^2 + q^2). The phase of the signal is atan2(Q,I). Note that the FFT transforms Voltage samples into Voltages per frequency bin. When you say energy you may mean power which is the magnitude squared or (i^2 + q^2). jeff, wa1hco Thanks Brad. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] GNU Radio Live SDR Environment 2014-0419 snapshot released
Hi John... Does the live CD run in a Virtualbox VM? It starts, but seems to hang the whole OS after trying almost anything. I'm trying this under Ubuntu 14.04. jeff On 04/20/2014 12:55 PM, Johnathan Corgan wrote: The GNU Radio Live SDR Environment has been updated with a snapshot of the latest master branch version of GNU Radio, two new third party SDR applications, and corrections for hardware support of RTL-SDR dongles and some older Ettus Research USRPs. Produced by Corgan Labs, the Live SDR Environment is a bootable Ubuntu Linux DVD with GNU Radio and third party software pre-installed. It is designed for quick and easy testing and experimentation with GNU Radio without having to make any modifications to a PC or laptop. The latest version of the ISO image needed to create your own DVD is available via a Bittorrent client using: http://downloads.gnuradio.org/releases/gnuradio/iso/ubuntu-12.04.3-desktop-amd64-gnuradio.torrent This release includes the gr-dvbt DVB-T transmitter/receiver application by Bogdan Diaconescu and the experimental gr-mac MAC layer implementation by John Malsbury. Further information may be found at: http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioLiveDVD ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] UDP Interface to Linrad
Linrad (http://www.sm5bsz.com/linuxdsp/linrad.htm) transmits UDP packets containing a some header information and a stream of I/Q samples in a variety of formats. It seemed like an interesting exercise to use GnuRadio and GRC to source from those packets and build some digital receivers. I'm new to GnuRadio and ran into some problems that maybe people on the list can explain. - How to strip the header for every packet not just the first? - Why no int to xxx conversions? Seems like too be a hole not to have a workaround? - Are there coding examples for adding python code to top_block as a light weight alternative to developing a new block? - Labview has a wrapper block that loops over all the blocks within. Didn't see that concept in GRC, did I miss it? thanks, jeff ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
