How do you calibrate a radar gun/unit?

[Hockey9019]

Just wondering about this. A buddy of mine from HS got a radar gun thats a few years old and was moving so he asked me if I wanted it. Of course I said sure and I'll be getting it tomorrow.

Well I was looking around and noticed eBay had several radar guns/units for sale. Some with tuning forks and some without.

How do you use tuning forks and how do you adjust it?

For the LEO's that use radar at work, do you use tuning forks still? I know the majority auto-calibrate themselves or whatever.


Here are the pics he sent me:



Kinda beat up but he says it works. I know the model is a X-band and most departments don't use it and use better and more accurate systems. I thought about donating it to a department, but like I said, its outdated and doubtful they would use it.

Thought about cleaning it up, and selling it on eBay maybe?

[Aussie George]

Firstly, get in your car and drive past a cop doing radar at about 20 mph over the limit. Take real good notice of what your speedo reads as you go past him. Preferable that you use cruise control and a digital readout.

When he gives you the ticket for speeding, see if it matches your speedo reading. If it does, then you know your car speedo is 100%.

If it does not then you can calculate what your speedo reads at a certian speed.

For instance if you were doing 60mph past the Po-po and your ticket reads 62 mph, then you know you have a 2 mph variation on your speedo.

Then get your radar unit and find a long straight bit of road out of town with a large road sign on the side. Get a good run up and set your cruise control to 60 mph. Set your radar to static mode (if possbile). As you go past the sign, hit it with the radar and see what it reads. You can then use this to see if the radar is as accurate as the officer that gave you the speeding ticket.

if the radar unit you have has no static mode, you may need a friend to drive at you at 60 mph while you test the speed of your car with your radar.

Or you could try and buy some tuning forks....either way!:D

[mobrien316]

We sent ours out to be calibrated.

At the beginning of the shift and after each ticket, we check them internally and externally for proper calibration, but we don't calibrate them.

[ChesCopPodz]

They are calibrated by the state.

We test to make sure it's still accurate by hitting the internal test button which should always show a certain speed. Then put the tuning fork(s) in front of it to make sure it's registering the speed set by the fork.

If both tests show the speeds they're supposed to, it's tested accurate.

[greenlead]

Remember that radar units are radio transmitters and are governed by the FCC.

[APDSarge]

The rules governing the "calibration" will vary by state when used by law enforcement. (For instance some states may require certification1 time a year, some states just verify speed with tuning forks before using the unit, other states test more or less frequently.)

In Florida we (the police) do not "calibrate" the radar. The radar is taken to a certified FCC radio technician (every 6 months). The technician uses various equipment to ensure the unit is working properly and within specific tolerances.

Officers before their shift, verify the unit is working properly by running the internal tests, and verifying a speed with tuning forks. The tuning forks DO NOT "calibrate" the unit. They just ensure the unit is continuing to operate properly. The same tests are done at the end of the shift to ensure the unit is still functioning. (That way all speeds obtained during the shift are presumed accurate.) The officers are required to keep a running log of the tests, and have it and all the certificates available for court purposes.

Florida does not use "X" band.

[Hockey9019]

Thanks for the replies everyone.

I got it yesterday and played with it for a bit. It seems pretty accurate. Its about a mile or so off but not that bad.

Range is not the best but its the older technology. Wonder how much I could get on eBay for this?


Theres no audio so it couldn't be used for LE purposes anyway

[Valor55]

You can't "calibrate" the RADAR. That has to be done by the manufacturer or another laboratory.

The tuning forks test the RADAR that it is functioning properly. At the start and end of every shift, and when we change locations, our policy dictates that we test the unit and verify it is working properly. Every 6 months our tuning forks are tested for proper calibration and replaced if they aren't. If your tuning forks are calibrated properly then you will know your RADAR unit is functioning properly.

The procedure is that you gently tap the tuning fork on a solid surface. It will begin vibrating and you hold it in front of the antenna. The tuning fork is supposed to create a known reading on your RADAR unit (i.e. 35 MPH or 55 MPH.) You do this in each of the RADAR modes (stationary, moving opposite direction, moving same direction etc.) This test procedures with the tuning forks will help you determine that your RADAR is properly calibrated.

It would cost my agency over $20K per year to send all our RADAR units to the manufacturers for calibration. It only costs several $$$ for getting the tuning forks calibrated. They are only $35 per pair for replacing too.

[Oldbillplod]

We use a tuning fork, drive through, area check (pointing the radar in various directions to see if there is any interference) and a measured distance check.

[Coastie 585]

I remember seeing an officer(Member of the forum) "Tune" his radar. Pretty cool, but you have to know what you are doing if you want to gt it right.

[Hockey9019]

I think KenK was the one who said something to the effect of: I once was clocking everybody at 88mph. Finally we found out it was the fan of my patrol vehicle. That was a lot of tickets I gave out on mistake :D



I tried that with my vehicle but couldn't get it to do that

[Valor55]

I remember seeing an officer(Member of the forum) "Tune" his radar. Pretty cool, but you have to know what you are doing if you want to gt it right.

How were they doing that?

[Darin]

I think KenK was the one who said something to the effect of: I once was clocking everybody at 88mph. Finally we found out it was the fan of my patrol vehicle. That was a lot of tickets I gave out on mistake :D

Thats one fast fan....


Sometimes my RADAR will pick up my fan but only at about 12mph. As it tracks a vehicle, moving considerably faster, that 12mph reading goes away.

[Hockey9019]

Thats one fast fan....


Sometimes my RADAR will pick up my fan but only at about 12mph. As it tracks a vehicle, moving considerably faster, that 12mph reading goes away.

I'll look for that post. I had it as my sig for some time

[citcop]

My unit registers the fan in my vehicle quite often, but it's a week signal (and reads up to 39mph). The RADAR unit is going to display the strongest signal (unless you have the option of displaying 'fastest speed' on your unit) so it displays a vehicle as soon as it registers due to the much stronger signal.
We also send our forks out every six months to have them checked and replaced as needed. As for testing, we test at the beginning of shift, after each stop resulting in a citation, and at the end of shift.