So I have an incoming signal of 137.9 MHz and a sampling frequency of 1.4 MHz. Once sampled how do I calculate the aliased signal's new frequency? Bandwidth is 38 kHz with a subcarrier of 2400 Hz, if that information is relevant. Just looking for an equation to calculate the aliased frequency.

The hardware used is a RTL-SDR into a computer sampling at 1.4 MSPS.

This is the signal's information page:


  • $\begingroup$ If you're using RTL-SDR or some other SDR, it is almost surely doing some frequency shifting before the sampler. Can you clarify what your setup is? $\endgroup$ – MBaz Jul 16 '19 at 23:35
  • $\begingroup$ @MBaz Just update it $\endgroup$ – hevansa98 Jul 16 '19 at 23:38
  • $\begingroup$ OK, so the SDR is doing band-pass filtering and frequency shifting. You shouldn't have any aliases. If you have any, they depend on which signals are in the passband of your BPF, and your intermediate frequency. $\endgroup$ – MBaz Jul 16 '19 at 23:40
  • $\begingroup$ Look at this document if helps: aaronscher.com/wireless_com_SDR/RTL_SDR_AM_spectrum_demod.html $\endgroup$ – Fat32 Jul 17 '19 at 0:07
  • $\begingroup$ Oh wow! Thank you! $\endgroup$ – hevansa98 Jul 17 '19 at 1:36

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