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There is a new RTLSDR.dll file that can allow an R820T USB tuner to go down as low as 4 or 5 MHz. Performance may not be as good as a real expensive wideband SDR that low, but it does receive lower frequencies. This works great in SDRSharp but if I put this DLL in the directory with this program, it does not enable low band scanning. I am trying to check the noise floor on CATV return path which is normally 5-42 MHz and without this modified open source DLL, I can only use this application to check 24 MHz and up.

Is there any way to build this application with support for the lower frequencies? Here is the original article I followed to get the new DLL that enables the direct sampling modes for pre 24 MHz tuning in this dongle: http://www.rtl-sdr.com/direct-sampling-mode-hardware-modifcations/

Thank you for your help!