Opinion ID: 1710982
Heading Depth: 2
Heading Rank: 2

Heading: Manual Tuning Fork

Text: A special tuning fork can be used to check the calibration of traffic radar. The special tuning fork is not to be confused with the forks used to tune musical instruments. The radar check fork is specially calibrated for checking a radar unit. The fork is tuned to vibrate at a frequency equal to the doppler frequency for some set speed, usually at 60 M.P.H. The speed check value will be stamped into the handle of the fork. The calibration fork is used as follows: Aim the antenna head upward away from any targets. Strike the fork on a plastic or wooden object to get it vibrating. Hold the vibrating fork in the radar beam approximately 4 in front of the radar head. Be careful not to move the fork while checking the meter reading. Check the meter reading; it should read the same speed as stamped on the fork handle. If it does not, the radar unit must be recalibrated as described in the operator manual. The use of the fork, as outlined above, modulates the radar beam so that the receiver is supplied with a signal equivalent to the normal doppler signal. The radar unit thus sees a signal equal to that coming from a vehicle traveling at a speed exactly equal to the speed stamped on the fork. When using a manual fork, care should be taken not to strike the fork hard enough to dent or damage it. A typical 60 M.P.H. manual tuning fork will have an accuracy of ± 0.2 M.P.H.