loud spurs in audio output
Posted: Wed Aug 15, 2018 5:11 am
Hi All,
I've been doing some great things with my relatively new RSP1A, using linux and cubicsdr program. Ever since the first time I got it running, I've been noticing high pitched audio whine in the speaker from my system whenever I use the RSP1A however. Today, I learned why the whine is so annoying using audacity to plot the output spectrum. Note that the whine IS NOT dependent on the frequency of operation of the RSP1A.
The whine is so annoying because it is about 5 different frequencies, not just one. And, the 2 largest spike in the audio output spectrum are many db above the average baseline!
I made 2 plots on 2 different aircraft band frequencies. I have attached the screen captures of the cubicsdr screen used to take the measurements and the spectral analysis of the output frequencies as displayed with the audacity 'analyze' command. And, I've attached 3 second .wav files for both the different receiver frequencies.
What the spectrum plots show is a nasty output spike at 999Hz and a second nasty output spike at 1904Hz. The spikes are 14.5 db above the noise floor at 999Hz and 13db above the noise floor at 1904Hz, the other spikes are higher in frequency, but range from 4 to 7db above the noise floor. Plots from both frequencies show the same frequencies and amplitudes.
I very often do plots of audio spectrum on my punchbox, the frequency spikes seen from the RSP1A are not due to any quirk in my computers sound system.
Does anyone know why these spikes are there or how to eliminate them?? They're annoying as heck::>
Regards,
Art
Please note, I tried to submit all five files, including the .wav files, so others could hear what I was hearing. The forum software will not allow submission of the other file types, so I could only upload the spectral analysis screen captures. I'll happily supply the other attachments by email-drop me a line if you'd like to have the other wav file and documents....ky1k attt myfair-point ddoott nett......delete the '-' in 'fair-point'.
I've been doing some great things with my relatively new RSP1A, using linux and cubicsdr program. Ever since the first time I got it running, I've been noticing high pitched audio whine in the speaker from my system whenever I use the RSP1A however. Today, I learned why the whine is so annoying using audacity to plot the output spectrum. Note that the whine IS NOT dependent on the frequency of operation of the RSP1A.
The whine is so annoying because it is about 5 different frequencies, not just one. And, the 2 largest spike in the audio output spectrum are many db above the average baseline!
I made 2 plots on 2 different aircraft band frequencies. I have attached the screen captures of the cubicsdr screen used to take the measurements and the spectral analysis of the output frequencies as displayed with the audacity 'analyze' command. And, I've attached 3 second .wav files for both the different receiver frequencies.
What the spectrum plots show is a nasty output spike at 999Hz and a second nasty output spike at 1904Hz. The spikes are 14.5 db above the noise floor at 999Hz and 13db above the noise floor at 1904Hz, the other spikes are higher in frequency, but range from 4 to 7db above the noise floor. Plots from both frequencies show the same frequencies and amplitudes.
I very often do plots of audio spectrum on my punchbox, the frequency spikes seen from the RSP1A are not due to any quirk in my computers sound system.
Does anyone know why these spikes are there or how to eliminate them?? They're annoying as heck::>
Regards,
Art
Please note, I tried to submit all five files, including the .wav files, so others could hear what I was hearing. The forum software will not allow submission of the other file types, so I could only upload the spectral analysis screen captures. I'll happily supply the other attachments by email-drop me a line if you'd like to have the other wav file and documents....ky1k attt myfair-point ddoott nett......delete the '-' in 'fair-point'.