2 RTL-SDR dongles at the same time with GRC

GNU Radio
1

Hello

I am considering using 2 RTL SDR compliant dongles + GRC for some simple
interferometric application.
Having two
of such dongles, does anybody know if it is possible to have both
running as GRC sources?
If not, would it be possible
in theory (to be developed) or there is a strict architectural reason
preventing this?

Thanks in advance
Alberto

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2

On 08/23/2012 05:51 PM, Alberto T. wrote:

Assuming that you’re using the gr-osmosdr source block, you can specify
multiple devices:

rtl=0
rtl=1

And so on.

But be aware, there’s no way to identify a “specific” RTL device –
those numbers just mean “the first one that enumerated this time,
the second one that enumerated, etc”. For you application it may not
matter whether you know on any given run which one is
which.

Also, unless you can find a way to:

 (A)  Synchronize the reference clocks for the two RTL-SDR dongles

(relatively easy using a shared 28.8MHz oscillator)
(B) Synchronize the sample stream (HARD!)

You aren’t going to have much fun with interferometry.

–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

3

Concerning the B issue, may be you could synchronize the input sample
stream using an external reference pulse received by both sticks at the
same time?

Best,
Rafael D.