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

Skip Tavakkolian skip.tavakkolian at
Sun Aug 25 16:11:37 UTC 2013

if you are trying to process ADS-B from two different dongles, running two
dump1090's isn't a problem. i routinely run dump1090 and rtl_acars using
two dongles on the same machine simultaneously. when running two dump1090
process you must provide the device id for each and make sure both aren't
running their web servers on the same port.

a more useful setup is to have multiple receivers running on cheap servers
(e.g. raspberry pi) at different locations and then collecting and
correlating the data.  having receivers at different locations should yield
a larger coverage area.

On Sun, Aug 25, 2013 at 7:13 AM, Jiao Xianjun <putaoshu at> wrote:

> basically you are right.
> But there is signal processing algorithm to track two dongles
> sampling/oscillator error separately and compensate them separately. Thus
> we can get them synchronized finally after signal processing algorithm.
> What I need actually is that how to get two streams of sample from two
> dongles.
> Actually I notice that in dump1090 it put rtlsdr_read_async in a new
> created background thread, then there is a possibility that I create two
> thread to operate two dongles. But in this method, there should be some
> mechanisms to synchronize two threads. It is complicated.
> Anyone has simpler solution?
> Thank you.
> On Sun, Aug 25, 2013 at 9:49 PM, Thierry Leconte <
> thierry.leconte at> wrote:
>> Le 25/08/2013 15:13, Jiao Xianjun a écrit :
>>  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?
>>>  Each dongle have its own clock, so it will never be synchronized at the
>> sample level.
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