I would imagine it's illegal because you're transmitting without a licence?.

But all you would need is a small microwave transmitter on the correct frequency, and the detectors are pretty crude.

Pranks are done by stupid little kids who don't think about consequences.

The speeder's radar detector goes off by your device, he slams on his brakes and causes a huge traffic accident with people being maimed and killed.
Please grow up.

Yeah, thats what our professor said, they used a garage door opener, and modified it. I see no difference in using one, vs. a cop.!?!?!?

Some drivers cause accidents when a little squirrel runs across the road.
Sure they slam on the brakes when their radar detector alarms.

I've done this before. I started with a surplus X band Gunn diode waveguide mount, which is a small chunk of waveguide split down the middle with a gunn diode mount on one side and sometimes a detector diode on the other side. This is the hard part already built. In my case i was building a speed measuring device, so I added more circuitry to form a complete receiver. One day, after the project had long since been completed, I was annoyed at the speeders roaring down my street, so I took my little waveguide device, sat it on the tailgate of my truck out at the end of the driveway and wired a pushbutton switch in line with the DC power. Then as drivers came down the street I would push the button and watch them hit the brakes. Great fun. Believe me I had no sympathy for those that felt it necessary to go into a four-wheels-locked panic skid on my 30mph residential street.

X band is around 10.5 GHz. Back in those days part of my job was repairing radar guns for the police department that I worked for. I sometimes would test the finished units by taking them out on my off hours. I would park on the side of a high speed but not too busy section of road and operate the unit hanging off the side of my driver's side window. You should have seen the looks of passing motorists as they wondered why the police were now using 240Z ghost cars.

Here's an example of the hardware I used:
X-BAND MICROWAVE OSCILLATOR WAVEGUIDE CAVITY GUNN - eBay (item 110304681350 end time Nov-26-08 02:42:55 PST)

You need an antenna, but you can make a horn antenna by soldering some pcb material together.

Originally Posted by RadioRon

Believe me I had no sympathy for those that felt it necessary to go into a four-wheels-locked panic skid on my 30mph residential street.

Did the grannies driving behind the speeder survive rear-ending him and each other?

Originally Posted by audioguru

Did the grannies driving behind the speeder survive rear-ending him and each other?

Yes, happily they did.

I have seen grannies driving their electric wheelchairs faster than 30km.

*cough* cell phone jammer *cough*

My section of Canada has a new law that condemns using a cell phone when driving.
Everybody continues to chat on the phone while swerving around on the road and going thru red lights.

The traffic cops aren't looking. Maybe they should jam cell phones.