I'm not too familiar with the RF front end on your particular device. I was thinking the spikes were perhaps intermods. Is your receiver OTA or cabled? You can change the gain and check the amount the peaks drop to see if that's the issue. There's some good info in the DRS sponsor presentation from GRCon 2015 [1]
[1] http://www.trondeau.com/grcon15-agenda Paul Garver On Jan 19, 2017, at 7:03 PM, Marc Pàmies Massip <[email protected]<mailto:[email protected]>> wrote: Thank you Cinaed, After doing the test with a sample rate of 8MHz I saw that both columns are not always equal (as you can see in the image). I am not using any hub, does it mean that I should use another computer or it doesn't suppose a big problem? The hackrf_info command tells me that my hackrf's version is 2014.08.1. I will ask in the other mailing list if I should do a firmware update because I don't know how to check which is the latest version. Marc. On 19/01/2017 23:34:18, Cinaed Simson <[email protected]<mailto:[email protected]>> wrote: On 01/19/2017 01:28 AM, Marc Pàmies Massip wrote: > Oh, really? I was using a HackRF-One and sampling at 10MHz. I was betting on a RTL dongle. And I'm guessing SDR# is running on Windows. You should also try a WBFM channel - between 88-108 MHz. There could be Windows USB driver issues - or the version of the HackRF One libraries and utilities doesn't match the firmware. Try hackrf_transfer -r NUL -s 8000000 The two columns should be equal in magnitude - otherwise the USB/computer are to slow for 8 MHz sampling - which is minimum requirement. Don't use a USB hub. And post hackrf_info on the above information on the mailing list [email protected]<mailto:[email protected]> - someone on the list may have seen the problem before. I know next to nothing about Windows. > > Now I've tried with different sample rates (8MHz, 10MHz, 12.5MHz and > 16MHz) and the peaks are always there. Maybe it's true that they appear > more often for higher sample rates, but I am not able to make them > disappear. > > Marc. >> >> On 19/01/2017 9:38:34, Cinaed Simson wrote: >> >> On 01/18/2017 01:31 PM, Marc Pàmies Massip wrote: >> > Hi, >> > >> > Maybe this is a stupid question for experts in SDR, but I haven't >> find a >> > clear explanation yet. I know it is normal to have a DC offset in the >> > center of the spectrum, but I am surprised by the amount of static >> peaks >> > that I see sometimes in specific bands (you can find attached some >> > images to better understand what am I talking about). It is obvious >> that >> > those are not "real" signals, in fact when I re-tune the SDR peripheral >> > they don't move according to the frequency displacement. I want to >> > understand if it is due to a software problem (the screenshots were >> > taken from SDR#) or if it has something to do with the hardware (maybe >> > those are just harmonics from some kind of square signal, i.e clock). I >> > am worried because they are extremely strong and because of this I >> could >> > have trouble detecting weaker signals nearby. >> > >> > Summarising, my questions are: >> > >> > - What causes those peaks? >> > - Is it necessary to remove them for a proper signal detection? >> > >> > Thanks in advance, >> > >> > Marc. >> >> You haven't indicated what hardware you used or the sampling rate. >> >> Try reducing the sampling rate - the sampling rate used may be unstable. >> >> > >> > >> > _______________________________________________ >> > Discuss-gnuradio mailing list >> > [email protected]<mailto:[email protected]> >> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> [email protected]<mailto:[email protected]> >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio <test1.PNG> _______________________________________________ Discuss-gnuradio mailing list [email protected]<mailto:[email protected]> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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