I have two SDRs hooked up to two different computers, both radios tuned to the same frequency. They sample at 2Msps. What I would like to do is start up both (at 'about the same time'), and, after adjusting for the inevitability that one started before the other (cropping part of a signal), compare and see that I have the same signal.

I theorize that I won't, actually, have the same signal. Because while both radios are sampling at the same sample rate, the samples aren't captured at exactly the same time. Am I correct?

The target signal is flexible, but DVB, and FM radio stations are examples.

  • $\begingroup$ You will definitely not have the same samples: the radios are different, their clocks are different, and they see different noise; if you're in a fading environment, they're likely to see different fading. However, the baseband signals obtained by both radios should be very similar, if the noise and fading are not too bad. You can see this in practice: you can swap cell phones and move around, and the calls you get sound roughly the same. $\endgroup$ – MBaz Jan 23 '18 at 2:59
  • $\begingroup$ @MBaz - here: panoradio-sdr.de/tdoa-transmitter-localization-with-rtl-sdrs the author uses three different radios, and correlates the output signals. Given that the signals (sample values) are entirely different (as you've just described), how does he do this? I get he's using correlation but, the digital samples will be a totally different set for each. $\endgroup$ – horse hair Jan 23 '18 at 3:02
  • $\begingroup$ @horsehair well, that's what a correlation does. Can't put it better than "he does a correlation to correlate", to be honest. $\endgroup$ – Marcus Müller Jan 23 '18 at 9:34
  • $\begingroup$ @horsehair You should have included that information in your question. Notice that the three radios used for TDOA are very carefully synchronized. $\endgroup$ – MBaz Jan 23 '18 at 14:35
  • $\begingroup$ @MBaz - they're synchronized to a GPS tower - but regardless the values for each are different because, as you mentioned, there are things like fading, interference from other signals, etc.... $\endgroup$ – horse hair Jan 23 '18 at 17:13

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