Speed Enforcement Cameras

There are 3 schemes in use. The most common is a LOW-POWER radar that has a limited range of about 1000 feet (330 meters). The second method is LIDAR or laser detection, again a very low-power to hobble detectors. The third we are hearing about uses magnetic sensors in the street and those cannot be detected by normal devices.

There may be a ray of hope for the magnetic detector based units though. Many loop detectors radiate RF energy, and because they do, they may be subject to regulation by the FCC and Industry Canada.

I've been told (but to chicken to find out if true) that the low power systems do not work in inclimate weather. anyone else heard this?

Now why wouldn't radio waves travel the same distance in rain or fog? Well, yes there can be some impairment, but not enough to change the distance by more than 1 or 2 percent.

I haven't heard about the low power systems 'not working' in inclement weather, but I have heard that high and microwave rf are affected by rain & fog. I'm also interested in where the 1 or 2 percent figures come from.

A basic intro is at
http://en.wikipedia.org/wiki/Radio_propagation , http://en.wikipedia.org/wiki/Radio_propagation#Rain_scatteri...
and http://en.wikipedia.org/wiki/Radio_propagation#Absorption

Real world experience. The density of the rain or fog along with the size of the water drop affects the propagation. Unless you can't see the effective range distance, there isn't going to be much in the way of attenuation. K and L band and any operating above 12 GHz will be more affected by rain and fog than those operating at the lower frequencies.