Question about radar interference X and K band

[OpenRoad]

I was wondering - though I need someone who really knows....

Considering all of the X and K band sources, if a LEO sets up shop adjacent say to the local Walgreens that has K-band door sensors, would his gear be interfered with the signals from the nearby transmitter? Enough so that you could take it to court and just say - 'hey, he was using a K band radar gun and was using it next to an external source of K band signal'...... Or is the gear so tuned that those adjacent frequencies are not a problem?

[Freebird]

The x and k band sources at wallgreens are a low power source of radar. The leo will be using the same band, K for example, but the Leo's radar is a different frequency in most cases. Even if he was using the same exact freq as wallgreens it will not interfere with the operation of his radar gun and his ability to capture vehicles speed in the same area of the wallgreens k-band doors.



If it were that easy we could mount a k-band radar gun on our dash in constant on mode and it would become a k band radar jammer... But it doesn't work this way.

[nr2d]

I can't answer your question BUT I have wondered the same thing.

[djrams80]

I was wondering - though I need someone who really knows....

Considering all of the X and K band sources, if a LEO sets up shop adjacent say to the local Walgreens that has K-band door sensors, would his gear be interfered with the signals from the nearby transmitter? Enough so that you could take it to court and just say - 'hey, he was using a K band radar gun and was using it next to an external source of K band signal'...... Or is the gear so tuned that those adjacent frequencies are not a problem?

The quick answer is super duper unlikely. The professor answered this question quite eloquently in this thread:

http://www.radardetector.net/forums/...nsitivity.html

Because of the doppler shift, the police radar guns are looking for the reflected signal to be a number of Hz or KHz off of the transmitted signal. Anything outside this range is basically ignored by the gun.

The doppler shift for K-Band for 1 MPH is (approximately) 72 Hz. So the highest practical doppler shift would be around 14 KHz, the doppler shift for K-Band at 199 MPH (the approximate operational limit for many guns). For a motion sensor to interfere with the police radar, it would have to be within 14 KHz of the police radar. Most of the time, even two same-model radar guns are different in frequency by many MHz, since Gunn oscillators just aren't that stable, hence the +/- 100 MHz bandpass for K-Band. Even trying to purposely tune a motion sensor to be this close to the radar would probably be nearly impossible.

For example, if the officer had a K-Band radar unit at exactly:
24.150000000 GHz,

For a motion sensor to interfere it would have to be at:
24.150014328 GHz

... or closer in frequency.

For some rough odds, divide the 200 MHz wide police K-Band by 14328 Hz, and you end up with a 1 in 13,958 chance that a motion sensor's frequency would happen to fall close enough to the radar gun's frequency to interfere. Not likely to happen, but it IS possible.

[jimbonzzz]

Thx man, I was going to reply but you beat me to it

[djrams80]

Thx man, I was going to reply but you beat me to it

I replied with one of your replies. No way in hell I would know that kind of stuff if it weren't for you.

[OpenRoad]

Thanks. I figured as much but it sounded plausible.