Polarization of microwave door openers...

[MEM-TEK]

Hi everyone,

I decided to film a video showing the strong effects of the polarized radar emanating from microwave door openers. I used my 9500i for this video. You will see that orientating a modern RD (my 9500i) vertically versus horizontally greatly reduces the received signal strength from the door opener. Here is the video:

Microwave Door Opener Polarization Demonstration

Before you think of mounting your RD vertically to greatly reduce false alerts from modern K band microwave door openers, consider the fact that the off-axis sensitivity of your vertically mounted RD will be different compared to when it is mounted horizontally in its "normal" orientation. I haven't yet taken the time to either test or make videos of the differences in off-axis sensitivity when a RD is mounted vertically versus horizontally. Also consider the fact that very few RDs use neutrally flared horn designs. Most RD horn designs feature a predominately upward or downward flare. This means that, if you orient your RD vertically, off-axis sensitivity will be different towards the left of your car versus towards the right of your car.

[jimbonzzz]

Nice video...

In addition to the things that MEM-TEK mentioned, also consider the fact that modern radar detectors are designed to be mounted horizontally in the vehicle (with vertical polarization) for a very good reason: because of the effects the windshield plays on the microwave signals passing through it. The windshield has effects which are somewhat similar to commercial microwave "rotary vane attenuators". Horizontal components are heavily attenuated by the windshield, while vertical components pass through much more easily.

Most police radar is circular polarized, and will have both vertical and horizontal components. As stated above, because of the windshield's effects, the vertical components pass through easily, while the horizontal components are attenuated by several dB depending on the windshield's slope.

If you mount your detector vertically, it will be horizontally polarized, which doesn't match the polarization of the vertically polarized waves which more easily pass through the windshield. The result? Not only do you get reduced range from vertically-polarized motion sensors, but from circular polarized police radar as well. And of course, vertically-polarized police radar sources like the Stalker ATR.

Of course, if horizontally-polarized photo radar is your primary threat, then by all means mount your detector vertically.

[kgalvin]

wow, but how does it moving veritcal change the way it pick ups a singal

[MEM-TEK]

wow, but how does it moving veritcal change the way it pick ups a singal

If the radar source is polarized (door opener, Stalker ATR, and some photo radar and speed sign systems), then rotating your RD 90 degrees will either decrease or increase your RD's ability to pick up the signal since the horns in RDs are polarized too.

Its just like wearing polarized sun glasses. If you hold the glasses so that you can look through one of its lenses while rotating the glasses, you will see that the brightness of the sky changes or that the intensity of sunlight reflections off of water changes as you rotate them.

[kgalvin]

hmm, that is sum thing i would have never tought of. thanks for sharing the info.

[Freebird]

I was looking at the off axis test from gol on the STI, and here is something I had not considred. Mounted vertically I figured I could lose some off axis sensativity, but looking at the off axis diagrams, could it be possible to gain a little in the over the hill test. Seems like it would perform better in the over the hill and perform worse in the off axis.

Also you tested a 9500i against a automatic door and got less signal mounted vertically, but my STI picks up automatic doors more often and with more signal on the meter mounted vertically.. Could we be seeing different results from different detectors?

I would be interested to see if an STI mounted vertically performs better in over the hill, straight ahead and off axis testing. If it loses performance
or gains performance would be interesting.

[MEM-TEK]

I was looking at the off axis test from gol on the STI, and here is something I had not considred. Mounted vertically I figured I could lose some off axis sensativity, but looking at the off axis diagrams, could it be possible to gain a little in the over the hill test. Seems like it would perform better in the over the hill and perform worse in the off axis.

Also you tested a 9500i against a automatic door and got less signal mounted vertically, but my STI picks up automatic doors more often and with more signal on the meter mounted vertically.. Could we be seeing different results from different detectors?

I would be interested to see if an STI mounted vertically performs better in over the hill, straight ahead and off axis testing. If it loses performance
or gains performance would be interesting.

I don't think that you would see any change in distance in over-the-hill encounters since nearly all police radar guns are circularly polarized. I did also try my STi in the same test setup with the door opener and noted that the STi horn design for some reason was almost as good at picking up the polarized door opener radar compared to the 9500i when it was oriented vertically. I suspect the reason is that each STi horn uses a LNA. Jimbonzzz, what do you think?

[Freebird]

I have not noticed any difference in performance on ka at all Vertical.I parked on the shoulder testing with a 34.7 clone sign and mounted on the winshield or vertical didnt result in any noticable differance. But I seem to get more 1 to 3 beep alerts from automatic doors Vertical where making another few passes horizonal I get no alert at all.. I have a k band speed sign a block from home I can do a little more testing on... I think the only difference we will notice is automatic doors and no difference to actual police radar due to the circular polarization.... thanks for your input.

[Freebird]

I did some more testing with the k-band speed sign with interesting results. Mounted vertically I get 30% or more alert distance on every pass. When I had it mounted horizontal I stopped when the alert was 3 lights on the meter and turned it vertical and it goes from 3 lights to full alert all lights. It is amazing how much differance on this speed sign how being vertical is much more sensative. I would assume the difference must be the polarization, circular to vertical. Too bad this does not work with police radar, would be nice to get 30% more sensativity

[Eloi]

would be nice to get 30% more sensativity

With Via Gra ...you can