MOST OF US ARE familiar with the radar speed guns used by
traffic police to detect speeding motorists. If you’ve been caught speeding
yourself and have had to pay a hefty fine, you probably don’t want to know any
more about them. But if you’re a car or bike racing enthusiast, you may well
have wanted one of them yourself, so you could measure the speed of cars or
bikes.
In these articles we’re going to show you how to build a Radar
Speed Gun of your own – for much less than the cost of a professional unit. It
can measure the speed of cars, bikes, horses, runners or even boats with a bit
of ingenuity. It’s compact and light in weight, can read directly in either km/h
(kilometres/hour) or mph (miles per hour), and operates from 12V DC. There’s
also a hold switch to enable you to freeze the reading.
The system is in two parts. There is a microwave head unit in a
small shielded box which is mounted on the underside of a cylindrical antenna
housing made from two 500g coffee cans joined end-to-end, to form the radar gun
assembly. This is linked by a cable to a counter/display unit housed in a UB1
jiffy box.
