Hi Jeff. If you do a Google search for sports radar gun, you can find numerous ones for sale. Personally, I don't think it's worth the few $100 dollars even up to $500. May I ask why you would buy one? How fast a person serves has always been a curiousity, and adds to bragging rights, but if you can't get it in the service box, hitting a fast serve doesn't really do much good. There's also been lost of sports studies as documented in the book Physics and Technology of Tennis, $20. It talks about string tension, racquet stiffness, weight and how it affects the speed of the ball. Basically it comes down to swing speed and racquet head velocity. Very interesting reading.
Hi, Thank you for your input. I did find one. It's actually a bet between friends. ;) Of course, we only measure the speed of the balls that we serve in the box. No box, no point. Thank you for the book referral, yes, I am very familiar with the physics and technology of tennis. It is very interesting. ~Jeff