[BC] chain link fence effect on satellite dish?

[r.j.carpenter]

I don't believe anyone has mentioned that the dish is probably not 
uniformly illuminated by the feed.  They don't want to illuminate the 
earth behind the dish and get 300-deg K noise from it instead of sky 
noise temp. I think this means that the outer portions of the dish 
contribute less to the gain that their area would suggest. Obscuring s 
bit of the outer area of the dish shouldn't decrease the gain a lot, but 
might increase the noise temperature.

Or am I as stupid as usual?