Re: [Discuss-gnuradio] static peaks spectrum

[Cinaed Simson]

On 01/19/2017 04:01 PM, Marc Pàmies Massip 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?

It's close enough.

You should use a binary search and find the maximum sampling rate.

This is the maximum sampling rate without the CPU load of the SDR on the
computer.

Then a crude rule of thumb would be to use half the maximum sampling
rate as a starting point.

We don't know anything about your computer so we can't comment.

Have you tried listening to a wide band FM station - or listening to
audio on any other band than 900 MHz?


> 
> 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 <address@hidden> 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
>>
>> address@hidden
>>
>> - 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
>> >> > address@hidden
>> >> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>> >> >
>> >>
>> >>
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