Ramsey Electronics BS1 Manual de instrucciones descargar pdf (Pagina 30)

SG7• 30

FINAL CALIBRATION:

To put it simply, the SG7 is calibrated by adjusting the control while pointing

the antenna unit at a vehicle traveling at a steady, known speed. Obviously,

the accuracy of the radar unit depends on the steadiness of the test drive

and the accuracy of the vehicle's speedometer. To verify speedometer

accuracy, use a stopwatch to time how long it takes the vehicle to travel a

given distance and carry out the appropriate calculations.

If the speedometer accuracy seems questionable, and no other test vehicle

is easily available, simply set up a safe test-run course to clock the car for a

certain speed. For a test speed of 30 mph., the car would cover half of 5280

feet in a minute, (that is 2640 feet in 60 seconds) which would result in

these test runs which are reasonable in length and sufficient time for

accuracy:

2640/6 = 440 feet in 10.0 seconds

2640/10 = 264 feet in 6.0 seconds

2640/12 = 220 feet in 5.0 seconds

Believe the time-distance results rather than the speedometer. If the car

consistently covers 440 feet in 10.0 seconds with the speedometer reading

27 mph, then have the driver drive at an indicated 27 mph as you calibrate

the SG7 for 30 mph. You can use any test speed which is safe for the

purpose, and the same procedure is used for kilometer/hour calibrations as

well. A bicyclist maintaining an accurate speed in the 15-20 mph range can

also do the job. If you are curious as to how radar guns are otherwise

calibrated, the procedure requires the use of a test device able to generate

a "false target"; simply a microwave signal of a known frequency that is

different from the fundamental frequency of the radar gun being calibrated.

Differences between the radar gun's frequency and the standard test

frequencies of the calibrating device are marked as test standard speeds

(25,35,55 mph, etc). A very informative construction article for exactly such

a test device was published in the Electronics Experimenters Handbook, an

annual publication of Radio-Electronics Magazine (Gernsback Pub., Inc.,

500-B Bi- County Blvd. Farmingdale, NY 11735)

Gain control adjustment:

After calibration, point the unit up into the air and adjust the gain control

clockwise until you just start to see a reading of 3 or 4. This will set the gain

at just below the maximum unstable point and give the best range. This

adjustment is somewhat critical, so take your time in doing it.

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Ramsey Electronics BS1 Manual de instrucciones Pagina 30