I found this from 2010, that uses GNU radio piped into a soft modem: http://oz9aec.net/radios/gnu-radio/connecting-gnu-radio-to-the-multimon-software-modem http

I found this from 2010, that uses GNU radio piped into a soft modem: http://oz9aec.net/radios/gnu-radio/connecting-gnu-radio-to-the-multimon-software-modem http://oz9aec.net/radios/gnu-radio/connecting-gnu-radio-to-t... Which would be the easiest way, unsure if you could do it purly in GNU Radio as not that up upon it, though software modems been around for a while, and more optimised code for the task. Historically the earliest software modems date back to the 90's.