Well, you can still do it. You just have to dig a little for the code. And you can use Active radar. Commercial radar guns that are available for consumers, so

Well, you can still do it. You just have to dig a little for the code. And you can use Active radar. Commercial radar guns that are available for consumers, so there must be frequencies allocated to use this legally https://www.amazon.com/Bushnell-101911-Velocity-Speed-Gun/dp/B0002X7V1Q https://www.amazon.com/Bushnell-101911-Velocity-Speed-Gun/dp... (though if you build your own device, it won't have specific FCC certification, but if you operate with in the same parameters -- frequency and power -- you're extremely unlikely to be noticed or penalized.)