Dear all, I'm calculating the RMS value of a signal with the following setup
RF vector signal generator -> USRP/rtl-sdr/... -> "RMS" block in GRC. Please bear with me - I'm not interested in the exact (absolute) voltage level. What I can't explain is why the calculated RMS value consistently shows a higher value when the signal is modulated (e.g. has a higher peak/average power ratio) compared to CW (unmodulated sine wave) For instance, RMS value shown in GRC for band-limited Gaussian noise is always around 2.5 dB _higher_ than RMS of CW of equivalent power (equivalent power according to the generator level setting and a spectrum analyzer with a power meter function). Similarly, 100% AM modulated signal shows around 1.3 dB _higher_ RMS. This effect appears with a USRP, rtl-sdr dongle as well as some custom hardware, so it doesn't seem to be something device-specific. Also, all hardware effects on the receiver side I can imagine result in _lower_ gain for modulated signals. If anything, I would expect to see a _lower_ RMS when turning on the modulation. Some more details are in this blog post: https://www.tablix.org/~avian/blog/archives/2015/04/signal_power_in_gnu_radio/ Any ideas would be welcome. At this point I have a feeling I'm missing something obvious here... Thanks, Tomaž _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
