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Sample rate / filtering interaction on the xA4

Posted: Wed Sep 20, 2023 4:37 pm
by shc
Is there any documentation on how filtering configuration is handled on the xA4? I am using SDRangel as a test bed and am seeing behavior I do not understand. The receiver configuration is shown in the linked images. The input signal is at -60 dBm in all cases.

Sample rate 2083335 Hz and above:
  • The spectrum for a 1000.2 MHz signal looks like this. The signal strength is about right, but the noise floor looks strange.
  • At 1001.1 GHz we get this. The signal is aliased to ~999.02 MHz and is down by only ~15 dB.
Sample rate 2083334 Hz and below (1 Hz less than the case above):
  • The spectrum looks like this. The noise floor shape is textbook and there is no aliasing of out-of-band signals, but the amplitude is about 11 dB too high.
Receiver configuration takes noticeably longer when the sample rate crosses the 2083334-to-2083335 boundary. This magic frequency is 6.25/3 MHz, which seems more than coincidental.

Re: Sample rate / filtering interaction on the xA4

Posted: Thu Dec 14, 2023 8:46 pm
by adamusa
You can also find documents on how to handle filtering mapquest directions configuration on xA4 on the websites of FPGA chip manufacturers, such as Xilinx, Intel, Altera,...

Re: Sample rate / filtering interaction on the xA4

Posted: Sat Jan 27, 2024 10:07 am
by pablito1
I had such a thing, a long time tortured with the settings but in the end just bought a new( https://papas-games.com

Re: Sample rate / filtering interaction on the xA4

Posted: Tue Aug 26, 2025 8:46 pm
by HeadSoccer123
pablito1 wrote: Sat Jan 27, 2024 10:07 am I had such a thing, a long time tortured with the settings but in the end just bought a new( Head Soccer
I should probably look for something new too.