Speed Radar
Test and Calibration

Police radars should be tested at shift start. Some departments also require testing at shift end. For a dual antenna radar the operator should test each antenna, front and rear, separately.

Required Test

• Ensure Radar and Tuning Forks are in Calibration Period.
  Most states require a radar and it's tuning forks be tested by a certified shop, typically once or twice a year.
• Run and Pass Radar Self-Test.
  Self test automatically runs on power-up. Some departments require self test after a citation is issued and/or at end of shift.
• Test Radar with Tuning Forks.
  A full tuning fork test should be conducted at start of shift. Radar front and rear antennas should be tested separately.

Range Control Setting.

The Range Control Setting should be adjusted as needed. This setting is actually the receiver sensitivity setting. The Long Range setting is the most sensitive, and may make the radar susceptible to local interference.

Optional Test

• Test Radar against Vehicle of Known Speed.
  Test vehicle should have a calibrated speedometer. Best to run test at operational location.
• Interference Test.
  Set radar to Receive Only mode and scan for interference in area radar is operating (stationary mode).

Self-test

The degree a radar self-test and automatically adjust circuits varies with model and ranges from none or little to testing 50 percent or more of the electronics. Self-test only checks and adjusts a portion of the electronics. The radar should also be tested with tuning forks before use.

A police or sports microwave Doppler radar will register a speed from a vibrating tuning fork's narrow side, the higher the tone the higher the speed. A radar will also measure a tone from an audio speaker diaphragm. The radar is measuring the microwave reflection of the fork or speaker diaphragm - a complete end-to-end test.

All police radars come with 2 tuning forks (different speeds) tuned for that radar. The forks should be labeled with, Speed, Radar Frequency, and Serial Number for tracking and accountability.

Tuning Forks

- - - -

Speed (55 mph) Radar Band (Ka) Frequency (35.5 GHz) Serial Number (82243)

Stationary Mode Test
Testing the radar stationary mode is straight forward. Place a vibrating fork a few inches from the front of the antenna, the radar should read the speed the fork is calibrated to induce. To start the fork vibrating gently strike the top side against a hard object such as wood or plastic, not metal. Once the fork is vibrating place it a few inches in front of the antenna. The fork's "side" must be facing the antenna to register a speed reading. Repeat the test using the other tuning fork.

Moving Mode Test
Two tuning forks with different tones are required to test moving mode. One fork simulates the patrol car speed, the other fork simulates a moving target reflection. The moving mode opposite direction traffic test is slightly different from the same-lane traffic test.

Opposite Direction mode
1	Strike both forks
2	Place SLOWER larger fork in front of the antenna.
3	Radar should read the fork as PATROL SPEED.
4	Place FASTER smaller fork in front of the antenna.
5	Radar should read the speeds DIFFERENCE .

Same-Lane mode
1	Strike both forks
2	Place FASTER smaller fork in front of the antenna.
3	Radar should read the fork as PATROL SPEED.
4	Place SLOWER larger fork in front of the antenna.
5	Radar should read the speeds SUM .

Tuning Fork Test using
30 and 55 mph Forks

Display	Radar Mode
	Opposite	Same-Lane
Patrol Speed: Target Speed:	30 mph 25 mph	55 mph 85 mph

Tuning Fork Equations
The tuning fork resonance is equivalent a Doppler shift the radar converts to speed. The speed reading is based on;
- Radar Frequency
- Tuning Fork Tone (resonance)

Radar frequency can be estimated from speed and tuning fork resonance. This is an estimate because there is some tolerance in the fork tone, and the equation has inherent rounding errors when calculating transmit frequency.

Periodically (at least once or twice a year) the radar and it's tuning forks should be tested (calibrated) by a certified shop. Testing records should be maintained that include radar and forks tested, dates, test results, and the shop or laboratory that performed the test.