RDR-4B Wx Rdr Interpretation

[extricate]

Hi there,

I'm looking through the RDR-4B manual. Any idea what does the graphic below mean? Does it mean if the range is set at 20nm, the radar will look down 6,900ft below?

Side question: How do I understand the link between radar tilt and range? Am I right to think in terms of trigo? Say i'm at 40nm, if my tilt is 2 deg down, wx radar is scanning 8,487ft down? If I set it at 80nm, wx radar is scanning more downwards? And how do I operationalise this in real wx ops?

Thanks

[RUMBEAR]

The diagram is referring to RADAR Beam diameter. At 20NM its 6900', which means if you set the tilt to 0 then the beam will be 3500' above and 3500' below (I think RADAR experts would say is the simple description), or alternatively set tilt to -3.5 degrees and now it is scanning 6900' below the aircraft at 20NM.

Looks like the beam width is 3.5 degrees. So you can estimate the beam width in feet versus distance (from the aircraft/range) with simple mathematics.

[Skyjob]

As RUMBEAR said, too many people however not being aware of the beam width and what thus the information on the screen in front of them represents