CHIRP

RT systems cables often don't work; they have built-in circuitry to make them work only with proprietary software.

You should look into purchasing a (good quality) cable from other sources. Ensure that you don't fall for a cheap product: these might come with rip-off versions of USB-to-Serial circuits, which might be refused by the corresponding driver detecting a fake.

Also, please refer to these Wiki documents:
Cable guide [[[https://chirp.danplanet.com/projects/chirp/wiki/CableGuide]]]
FTDI and RTSystems cable guide [[[https://chirp.danplanet.com/projects/chirp/wiki/CableGuide_FTDI_OEM_Cables]]]
RTSystems cables and OSX [[[https://chirp.danplanet.com/projects/chirp/wiki/RTSystemsCablesAndMavericks]]]