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Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of
From: |
Juha Vierinen |
Subject: |
Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles |
Date: |
Thu, 26 May 2016 07:28:13 -0600 |
I was using a dongle with r820.
juha
> On May 25, 2016, at 23:27, Piotr Krysik <address@hidden> wrote:
>
> Juha,
>
> What type of demodulator did you have in the dongles used for the test?
>
> --
> Piotr
>
> W dniu 25.05.2016 o 14:46, Juha Vierinen pisze:
>> In my testing, this phase rate difference seemed constant and I could
>> simply calibrate it out by looking at the phase rate term estimated
>> from the phase of the cross-correlated noise. The samples stay aligned
>> for hours, so the issue is caused by the tuner or the DDC. One theory
>> that I had was that the multi-rtl driver somehow sets up the dongles
>> differently, but I never got around to looking at the code.
>>
>> I think this was the script I used to figure out what the phase drift was:
>> https://github.com/jvierine/chirpsounder/blob/master/apps/passive_radar/rnoise.py
>>
>> Here's the IQ plot to prove that the cross correlated phase is stable
>> over 6000 seconds:
>>
>> http://kaira.sgo.fi/2013/09/16-dual-channel-coherent-digital.html
>>
>> juha
>>
>> On Wed, May 25, 2016 at 12:14 PM, <address@hidden
>> <mailto:address@hidden>> wrote:
>>
>> From our own experience with dual-dongle measurements, the phase drift
>> seems to be strongly related to R820T(2) temperature. We reduced
>> significantly
>> the phase drift by gluing a large heat sink common to both chips
>> on both
>> dongles, without completely removing this effect (we aim at
>> measurements lasting
>> multiple hours). At the moment the only option we could think of
>> (mail to this
>> mailing list dated 28 May 2015) is switching to a reference clock
>> to calibrate
>> for the phase difference between the local oscillators, but the
>> actual cause
>> of the drift remains a mistery (probably due to the implementation
>> of the PLL,
>> but I cannot understand why Phase Locked Loops would drift in
>> Phase !).
>>
>> JM
>>
>>> It wouldn't be as simple as it was for me as a developer and as it
>>> (hopefully) is for the end user without your hardware mod.
>>>
>>> Can you say something more about the residual center frequency
>>> difference? Where might it come from? I prepared little test of
>>> coherency between the receivers
>> (multi-rtl/examples/test_multirtl.m).
>>> Among all the figures that it shows there is a plot of relative
>> phase
>>> offset of signals coming from the receivers. In fact I have seen
>> linear
>>> phase change on that plot - that corresponds to some central
>> frequency
>>> offset. If I know what is the source of this offset maybe I will
>> be able
>>> to find some way to fix it in software.
>>>
>>> --
>>> Piotr
>>>
>>> W dniu 25.05.2016 o 08:24, Juha Vierinen pisze:
>>>> This is awesome! I'll definitely try this out soon. I use one off
>>>> python scripts to find the sample offset and the small
>> residual center
>>>> frequency difference. This simplifies the process significantly.
>>>>
>>>> This should make it much easier to implement a passive radar
>> block, or
>>>> an interferometry block.
>>>>
>>>> juha
>>>>
>>>> On Tue, May 24, 2016 at 4:03 PM, Piotr Krysik <address@hidden
>> <mailto:address@hidden>
>>>> <mailto:address@hidden <mailto:address@hidden>>> wrote:
>>>>
>>>> Hi all,
>>>>
>>>> I want to announce new GNU Radio related project prepared
>> by me -
>>>> Multi-rtl:
>>>> https://github.com/ptrkrysik/multi-rtl
>>>>
>>>> It is a Gnu Radio block that combines multiple RTL-SDR
>> receivers into
>>>> one multi-channel receiver.
>>>>
>>>> Only hardware modification to RTL-SDR dongles required is
>> connecting
>>>> them to a common clock source (i.e. one of the dongles'
>> oscillator as
>>>> Juha Verinen showed once). Each channel can work on a
>> different
>>>> central
>>>> frequency.
>>>>
>>>> Everyone who wants to know how it was achieved is invited
>> to read my
>>>> github page:
>>>>
>>>> https://ptrkrysik.github.io
>>>>
>>>> Best Regards,
>>>> Piotr Krysik
>>>>
>>>> _______________________________________________
>>>> Discuss-gnuradio mailing list
>>>> address@hidden <mailto:address@hidden>
>> <mailto:address@hidden <mailto:address@hidden>>
>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>
>>>
>>> _______________________________________________
>>> Discuss-gnuradio mailing list
>>> address@hidden <mailto:address@hidden>
>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>>
>> --
>> JM Friedt, FEMTO-ST Time & Frequency/SENSeOR, 26 rue de
>> l'Epitaphe, 25000 Besancon, France
>
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, (continued)
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, Piotr Krysik, 2016/05/25
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, jean-michel.friedt, 2016/05/25
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, Sylvain Munaut, 2016/05/25
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, Marcus Müller, 2016/05/25
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, mleech, 2016/05/25
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, Piotr Krysik, 2016/05/25
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, mleech, 2016/05/25
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, Piotr Krysik, 2016/05/26
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, Juha Vierinen, 2016/05/25
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles, Piotr Krysik, 2016/05/26
- Re: [Discuss-gnuradio] Multi-rtl - making multi-channel receiver out of multiple RTL-SDR dongles,
Juha Vierinen <=