The datasheet. for the feedhorn states it has an adjustable beam width

F/D of 0.32 to 0.43. Now, the calculator here tells me that my 2.4m dish

has a F/D of 0.38, OK so far. There are 2 graphs on the datasheet.

From the first one, I can see that for a F/D of 0.38, I need to screw the

feedhorn in for a 4mm protrusion. (I guess this means the thread is

protruding 4mm proud of the corrugations).

The problem I have is with the second graph. The "Y" axis has no units.

The 4mm protrusion from graph 1 seems to correspond to "120" on the

second graph - but I don't know what it's 120 of. Can anyone shed any

light on what this graph signifies?

Thanks,

Pete