I first found Jack audio on Linux, this video shows it on Windows. Simple use may only need the ASIO Bridge, for that skip to 10m49s
HERE ARE THE LINKS MENTIONED IN THIS VIDEO:
1. download for windows version of JACK AUDIO CONNECTION KIT
http://jackaudio.org/downloads/
2. tutorial on installing JACK AUDIO on windows
http://www.jackaudio.org/faq/jack_on_windows.html
3. download for KXSTUDIO Carla, and Cadence(Catia) for windows
http://kxstudio.sourceforge.net/Downloads
5. download VB-AUDIO ASIO BRIDGE
http://vb-audio.pagesperso-orange.fr/Cable/
6. download ASIO4ALL (optional) if you don't have a "true" ASIO SOUND CARD
http://www.asio4all.com/
In SDR, you may need to patch from one application to another. Here are some other ways to do it:
http://www.rtl-sdr.com/a-list-of-5-free-virtual-audio-cable-software-programs/