How do I download xcode 7.3 w/o paid developer account?

I need to install Xcode 7.something (let's say 7.3.1).

I'm still running OS X Yosemite - the App store only shows Xcode 8, even my Yosemite doesn't meet the requirements.

I'm not a paid developer, how can I get the older Xcode version (which is the only one that will run?)

I just need the tools to run the GNU Radio environment, so I don't need swift, or any IOS development tools.