Clear Waves is described as 'is the next generation of PC-based, RF spectrum analyzer for the wireless pro audio and video industries that offers automatic charting of open white space, frequency coordination and channel assignment'. There are three alternatives to Clear Waves for Windows, Linux, Mac and Online / Web-based. The best alternative is WaveTower. It's not free, so if you're looking for a free alternative, you could try HackRF.
WaveTower® (formerly Vantage) is a patented platform from RF Venue that allows you to remotely monitor and manage RF spectrum activity over the web and on your Mac desktop. Monitor and manage local RF conditions from across town or across the globe.