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Peak in FFT.

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	Peak in FFT. by Kóczián Gergely :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message Hi all! I use my usrp without antenna. I just want to meassure the noise but, at 0Hz has always a peak. I saw that, this was a probleme in the past also, but i didn't found the solution. Attached picture: http://img4.imageshack.us/img4/2493/messung11.png What did I wrong? Best Regreads: Gergely _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@... http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
	Re: Peak in FFT. by Matt Ettus :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message Kóczián Gergely wrote: > Hi all! > > I use my usrp without antenna. I just want to meassure the noise but, > at 0Hz has always a peak. > > I saw that, this was a probleme in the past also, but i didn't found > the solution. > > Attached picture: > > http://img4.imageshack.us/img4/2493/messung11.png > > What did I wrong? What daughterboard are you using? Matt _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@... http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
	Re: Peak in FFT. by Karthik-28 :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message On Thu, Nov 5, 2009 at 10:25 PM, Matt Ettus <matt@...> wrote: > Kóczián Gergely wrote: >> >> Hi all! >> >> I use my usrp without antenna. I just want to meassure the noise but, >> at 0Hz has always a peak. >> >> I saw that, this was a probleme in the past also, but i didn't found >> the solution. >> >> Attached picture: >> >> http://img4.imageshack.us/img4/2493/messung11.png >> >> What did I wrong? > > What daughterboard are you using? > > Matt > From the attached screen shot it looks like you are using a LFRX daughterboard. Do you have 50ohm output impedance from your source? You can try terminating your channel with a 50ohm terminator and see if the peak goes away. Karthik _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@... http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
	Re: Peak in FFT. by Kóczián Gergely :: Rate this Message: Reply to Author \| View Threaded \| Show Only this Message Yes I use LFRX. Thanks the suggestion, i will try. 2009/11/7 Karthik <karthik1024@...>: > On Thu, Nov 5, 2009 at 10:25 PM, Matt Ettus <matt@...> wrote: >> Kóczián Gergely wrote: >>> >>> Hi all! >>> >>> I use my usrp without antenna. I just want to meassure the noise but, >>> at 0Hz has always a peak. >>> >>> I saw that, this was a probleme in the past also, but i didn't found >>> the solution. >>> >>> Attached picture: >>> >>> http://img4.imageshack.us/img4/2493/messung11.png >>> >>> What did I wrong? >> >> What daughterboard are you using? >> >> Matt >> > > From the attached screen shot it looks like you are using a LFRX > daughterboard. Do you have 50ohm output impedance from your source? > You can try terminating your channel with a 50ohm terminator and see > if the peak goes away. > > Karthik > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@... http://lists.gnu.org/mailman/listinfo/discuss-gnuradio