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

Jiao Xianjun putaoshu at
Mon Aug 26 02:56:32 UTC 2013


Yes, you are right. The thought is kind of message combination or
information fusion, diversity receiving. In this situation, large distance
spaced antennas/dongles are required to get enough diversity.
But in some application, such as beam forming, direction finding, we want
to have antennas/dongles located in a strict relation ship, such as
lambda/2 spaced antenna array. In this case we want to detect carrier
phases of each channels.

On Mon, Aug 26, 2013 at 12:11 AM, Skip Tavakkolian <
skip.tavakkolian at> wrote:

> 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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