Subreflector Gain Characteristics
Jim Breakall
April 19, 2015
Subreflector is modeled as a circular parabolic reflector with various focal lengths. Focal Length chosen for original design is 136 feet. The depth of the parabolic reflector can be found from the following formula:
Depth = Diameter ^2 / (16 * Focal Length)
Diameter of Subreflector at widest is 370.4 feet. That is used here for the circular parabolic reflector.
Focal Length (ft) 
Subreflector Depth (ft) 
Gain (dBi) 
50 
171.4 
17.67 
100 
85.7 
20.63 
136 
63.0 
22.14 
150 
57.1 
22.36 
200 
42.9 
22.26 
300 
28.6 
21.21 
Flat Disk 

17.9 
Gain (dBi) 

150 
13.27 
175 
20.62 
200 
21.65 
225 
20.88 
250 
19.68 
260 
19.99 
270 
21.02 
280 
22.17 
284 
22.14 
290 
21.74 
300 
21.14 
350 
20.24 