How to prevent Radio test from stopping with cli disconnected?

Hi Devzone:

We put the radio test project on our custom battery powered board and encountered a problem.

When we disconnect the usb cable, the tone emitted by radio test project disappeared.

We want to disconnect the cable as the cable could act as an antenna.

Why the radio test needs usb cable connected to keep running? Where can I modify the code so that disconnecting cable would not stop the test?