To reduce PC-induced noise entering the SDR-RTL via USB and antenna, the RTL-SDR should not be mounted directly to the PC's or any other USB host's (e.g. display) USB connector, but via USB extension cable and ferrite filter element at some distance (say at least half a meter). 

When installing the RTL-SDR this way and connecting a long antenna it may tople over. I designed a simple holder to avoid this.

This holder fits the RTL-SDR V3 from www.rtl-sdr.com. You may adapt it to other RTL-SDR dongles, see below.

As always I include the OpenSCAD source file for you to adapt and/or improve:

• Download and install OpenSCAD from https://www.openscad.org
• Launch OpenSCAD and open the enclosed OpenSCAD source file (/File/Open).
• Amend the parameters at the top of the source file or even code.
• Save your changes (/File/Save).
• Render the design (/Design/Render).
• Export the rendered design e.g. as a .stl file (/File/Export/Export as STL).
• Slice and print.

See my other designs at
https://www.thingiverse.com/thinger13/designs