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ManInTan
10-28-2008, 06:41 PM
Can anyone explain how/what a tuning fork is used for with Police Radar Units? We have one car that has a tuning fork hardmounted to the dash. I thought maybe they were only used for initial installation... Anyone know whats up with this?

SoCalSheriff
10-28-2008, 06:56 PM
While I do not know the exact procedure, I saw one of our traffic guys playing with the tuning forks one day. He told me they use two different frequencies (sorry, I do not know which two). One represents 35mph, the other 55mph. He would hit the fork and pass it by the radar reciever. The display would sow the speed. I believe the speed had to be within 1mph of the intended reading to be considered calibrated. He told me he checks them at the start of every shift.

Hopefully someone with a little more experience can clear it up or answer better than I can.

ManInTan
10-28-2008, 11:46 PM
I'd buy that, Thanks!

31221J
10-29-2008, 12:59 AM
I use them every time before every shift. I know the tuning forks are set to the frequency of 35 mph and 55mph. They use the same frequency that the radar picks up a car with. When the tuning fork is struck (I use the dash) then put in front of the radar (while your radar is set to stationary) it should read what the frequency speed of the fork is. It is basically just a way of assuring your radar is in working order.

Groove
10-29-2008, 01:28 AM
So what your saying is I should mount a huge tuning fork to the hood of my car and i'm safe to fly home after work?

Guams
10-29-2008, 02:41 AM
I thought the tuning forks were set for 30mph and 55mph? Maybe they're different, but mine are 30 and 50. And, like has been noted, they're used to check the calibration of the radar unit. I do it during my squad check at the start of my shift and make a note in my patrol log.

Sabre
10-29-2008, 03:07 AM
For some reason, we don't do the "tuning-fork test" in Michigan. My radar instructor said that the Michigan Speed Measurement Task Force doesn't allow it.

Anybody know why?

(We're also not allowed to use the "fastest target" window. What gives?)

nebraska_deputy
10-29-2008, 03:34 AM
For some reason, we don't do the "tuning-fork test" in Michigan. My radar instructor said that the Michigan Speed Measurement Task Force doesn't allow it.

Anybody know why?

(We're also not allowed to use the "fastest target" window. What gives?)

It must be a state thing.

Most places around here your taught to do it at least at the start and end of your shift. A lot of officers do it after every stop that they cite someone on. Always remember the forks along with the other test, Audible Tone, and lights are to CHECK the accuracy of the calibration of the unit.

If one of the three are not working, or the forks are off by more than a mile you shouldn't be using the radar unit. It should be placed out of service. As was told to me several times we don't calibrate the radars the manufacture comes out once a year and does that.

We were taught not to strike the tuning forks on one another to do our accuracy check either. Your suppose to use a hard surface, but not the other fork because it could change your readings or damage the forks. But from personally seeing other officers do it, I know it happens. There are several ranges of tuning forks that can be used. It all depends on what the department buys and or what the radar manufactures sell to the department.

Monty Ealerman
10-29-2008, 08:11 AM
http://tf.nist.gov/timefreq/general/pdf/87.pdf

Lawenforcer72
10-29-2008, 09:07 AM
you need to get your tuning fork from the maker of the radar. They are specially made to assure calibration of the radar. Its a must if you want to do traffic stops, and every defense attorney worth anything will ask you if you verified calibration.

Red Swan
10-29-2008, 11:15 PM
state law or radar law whatever requires radar to be calibrated with the forks before the start of every shift and ur suppost to keep a log of miles on the car, date, and results of the test.... but nobody really does that:D good reason to get a ticket thrown out here... ah whens the last time u calibrated ur radar officer..murr about once a month.. not guilty!

aaron1085
10-29-2008, 11:21 PM
dude, any GOOD judge will ask if you test your radar before your shift...testing it involves using a tuning fork.