rtl-sdr.com

SDR# must not be in "Program Files"
Alan

I suggest you try HDSDR v2.80.
Then report if it still has a problem.
Alan

This needs clarifying. IS it really a V3, the model with direct sampling? If so the -40000000 offset makes no sense. I note https://www.rtl-sdr.com/rtl-sdr-quick-start-guide/ mentions counterfeit ones. I do not know about RTL direct sampling with HDSDR just that a particular DLL has to be used and d...

" difficulties in getting HDSDR to match the sensitivity of SDRSharp" This I do not understand. The waterfall displays of various SDR software vary, some might be better at showing weaker signals visually but I never read any comments about the basic sensitivity varying between programs. This is set...

With raw IQ it can cover 48Khz or, with limitations, 192KHz.

1 RF Front End calibration
2 Think so, not sure
3 Presumably audio is the same? Sliders under the display adjust.
Alan

Bob,
Why the insistence on Sigmira?
If SDR# works why not use that?
Or HDSDR or SDR Console? These are far more popular, better known and work well.
Sigmira is only useful for the few odd modes it can decode, if you can find them on the air. If you can get it to work...
Alan

Stereo Mix act as a single cable.
Alan

"navigate to different bandwith's"? Sorry that makes no sense to me, you tune to frequencies. Bandwidth is basically the width of a signal depending on the mode. Too many questions, I can't help with DSD but there are frequencies where you might receive it? I guess the plugin helps you with all that...

About 2MHz is all you get in real time. There are programs that build up a spectrum in slices but that would take a long time to do 400MHz even if any actually is capable of such a scan.
I guess the RF Explorer uses a much higher sample rate.
Alan