otnmbrd wrote:
The other "blanking" is done by the computer to blank off the picture
over certain areas of the scan rotation where the radar image would
just show a more or less solid land return of no value to the viewer.
In both cases these are used on shore based sets and to be honest I
can see little if any value for underway shipboard use.

I believe (dredging up details from a distant memory of school) this is
called *masking*, whereas blanking is turning off the transmitter during
part of the rotation. Blanking is to prevent high powered returns
bouncing back into the receiver from metal objects in very close
proximity like mast-mounted antennas, and masking is to remove unwanted
clutter. The masking I remember was performed by the receiver ignoring
returns that were too close in time from being transmitted, like
stern-mounted antenna returns from the mast or rigging. Modern radars
(as opposed to the ones I learned on) also have a computer-controled, I
think processing that can selectively mask several types of returns like
sea returns that cause clutter. Of course this is all from rusty
memories, so it could be incorrect.