Near Intersection of I-35 & I-90 Southern Mn. | The one you show in your picture is very old. Back in those days the calibration number in many monitors was a fixed number so you adjusted the angle on the pipe to get the speed to work out correctly.
Later when monitors had the ability to allow the operator to input the calibration number, they started using a fixed angle for the bracket. The fixed angle that DJ used with their next model the RVS II was 37 degrees downward from "flat".
This is the classic 3-4-5 right triangle. In other words if you measured 4" forward and dropped down 3", the angle would be 37 degrees. Multiples of those numbers will be easier to work with. So for every 12" forward drop down 9". The radar gun can be pointed backwards if obstacles are involved. When using one with saddle tanks it is often hard to get an unobstructed view of the ground. Although not the most desirable, we found that as long as the obstacle (pipe bracket etc.) doesn't block off the area completely and doesn't move, the gun may work acceptably. A clear shot is always desirable.
Other angles could work if the calibration number was changed accordingly but I would try to get roughly the 37 degree angle and then adjust the calibration number as needed. An angle of 45 degrees is probably too steep.
I saw one instance where the angle used was the complement or 53 degrees down. This sort of worked by using a different cal number but the speed was not very stable and jumped around more than one wants. I recommend trying to get in the ball park of 37 degrees. From your picture I'm guessing you might be a bit more than that right now but possibly good enough.
Although this old radar gun might work fine for you, most of those that age have failed. I suggest having a backup plan such as a GPS hockey puck available in case this one fails for you.
Edited by tedbear 1/3/2024 15:54
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Old Dickey-John radar mounting specifications
