how do you know the little tilt knob is set right?
If you can't do the telegraph
then i guess we shouldn't expect you to be able to do the math but:
For ludites like Buzzy, if you want to check out the radar's calibration. Say you are at 40,000' and put the antenna 10 deg down (-8.5 tilt) you should see the ground return at 40nm.
That is how you know the little tilt knob is set right. Then a bit more remedial math will give you the cloud tops (liquid water).