How to get IQ samples from multiple rtl-sdr dongles in a synchronized manner?

Sdr Guru sdrguru1 at gmail.com
Mon Dec 30 11:01:38 UTC 2013


Hi

Are you using a common clock?
http://kaira.sgo.fi/2013/09/16-dual-channel-coherent-digital.html

I've modified some of the RTL dongles, played with GNURadio and Octave.
The results are promising, sample level correlation (2.4M/10, FM radio
signal).

On Mon, Dec 30, 2013 at 9:38 AM, Jiao Xianjun <putaoshu at gmail.com> wrote:

> Hi guys,
>
> For the multiple dongles synchronization in signal level instead of
> bits/packets level, I setup a working repo in github, and write a initial
> demo framework. See below:
>
> https://github.com/JiaoXianjun/multi-rtl-sdr-udp-relay.git
>
> You may find information and instruction of demo quickly by reading the
> README.
>
> My initial purpose is performing in-fly calibration for multiple dongles
> according to some pre-known signal (GSM, ADS-B?) to let them work together
> coherently.
>
> An ideal scheme may be that we should generate a very narrow band and very
> week signal in (or just located at the edge of) target working band of
> dongles, and perform the software in-fly calibration in background (or
> driver level). This would be user friendly.
>

Cheap (8USD+PP), simple, computer-controlled and legal FM band "marker"
http://blog.palosaari.fi/2013/08/naked-hardware-12-usb-audio-transmitter.html

 I know it is far from final state currently, and many things are not clear
> yet (See TODO). But please join me if you also think this is a good idea.
> Just check out the demo and run it to have a look.
>
Testing it and I'll let you know.


> Currently I just test the demo in Ubuntu-Linux.
>
>  BR
>
> Jiao Xianjun
>
>
> On Mon, Sep 2, 2013 at 8:23 PM, Sylvain AZARIAN <sylvain.azarian at gmail.com
> > wrote:
>
>> Thanks.
>>
>> sylvain
>>
>>
>> 2013/9/2 Sdr Guru <sdrguru1 at gmail.com>
>>
>>> The second way, use MLAT enabled dump1090
>>> https://github.com/antirez/dump1090/pull/23
>>> http://www.satsignal.eu/raspberry-pi/dump1090.html
>>>
>>>
>>> On Sun, Aug 25, 2013 at 4:13 PM, Jiao Xianjun <putaoshu at gmail.com>wrote:
>>>
>>>> Hi,
>>>>
>>>> I want to use multiple rtl-sdr dongles to do some multi-antenna
>>>> experiments.
>>>>
>>>> Is it possible to read IQ samples from multiple rtl-sdr dongles in a
>>>> synchronized manner?
>>>>
>>>> I already have a glance at dump1090 codes, which is a project using
>>>> rtl-sdr to decode aircraft broadcasting ADS-B messages in 1090MHz.
>>>>
>>>> Seems that I should use rtlsdr_read_async() instead of
>>>> rtlsdr_read_sync(), because that if rtlsdr_read_sync() is used, I have to
>>>> call it multiple times sequentially. That looks not synchronized.
>>>>
>>>> But rtlsdr_read_async() function only accept one rtl-sdr device as
>>>> input parameter, and it will be blocked after it is called. So seems that
>>>> it also can't be used for my purpose directly.
>>>>
>>>>  Also welcome any opinion on how to improve rtl-sdr lib/driver to
>>>> support this feature.
>>>>
>>>> Thank you.
>>>>
>>>> BR
>>>>
>>>> Jiao Xianjun
>>>>
>>>
>>>
>>
>
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