# Thread: what would happen if....

1. ## what would happen if....

you purchased a Ka unit (same frequency as used by your state/town) and stuck it in your car and transmited (i know its illegal to opperate) at the same time you were being targeted by an LEO running the same gun?

2. ## Re: what would happen if....

Originally Posted by againstme!
you purchased a Ka unit (same frequency as used by your state/town) and stuck it in your car and transmited (i know its illegal to opperate) at the same time you were being targeted by an LEO running the same gun?

Long answer: Could cause a false speed reading on the officer's unit, maybe in one case in a million (if you're lucky).

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. So, one radar unit would have to be VERY close to the other one in frequency. Really about the maximum two units could apart in frequency for one to cause a speed reading on the other (stationary mode) is 21KHz @ 35.5 GHz and 200MPH. But in practice this almost NEVER happens. Most of the time, even two of the same model of radar unit are different in frequency by many MHz, since Gunn oscillators just aren't that stable, hence the +/- 100 MHz bandpasses. Even trying to tune two units to be this close to each other on purpose would probably be nearly impossible.

For example, if the officer had a K-Band radar unit at exactly 24.150000000 GHz, to display a false speed of 55 MPH on the police radar (stationary), your gun would have to be at 24.150003962 GHz. So, not too likely :cry:

BUT, if you happened to be legally operating your own licensed radar unit in the vehicle at the same time you were ticketed for speeding, this might make a good argument in court :wink:

Jim

3. A freind and I once tested it with two K band units, although one was a MPH unit, and one was a Kustom unit.

There was no noticeable difference in the way they operated or measured the other cars speed. When the MPH unit was in standby, it did have a doppler audio tone when it was in the Kustom units radar beam, indicating it was getting some signal.

Ed

5. Originally Posted by ltilaser
If the unit was in moving mode, the situation would generally be the same as above. All that would change in moving mode is where the unit looks for a doppler return frequency. Still an extremely low possibility of it causing a false reading.

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