> Better to say Reflector dishes instead of reflecting disks.

I took your advice.

> All these dishes have essentially a parabolic meridian,...

if that means the surface is a surface of revolution. If so, the focus
must be in the center. But that TV disk has the receiving bar a bit
below the center, thus prompted me to suspect that the surface is not
parabolic. i.e. not a surface of revolution exactly.

Xah


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Better to say Reflector dishes instead of reflecting disks.

The TV dish receiver is not necessarily parabolic, since the focus is
below the center of the dish as we can clearly see in the photo.

Not clear what this means. All these dishes have essentially a parabolic
meridian, truncated at various depths. Dish designs have focal length f
/ Dish diameter d ratio ( known as f/d in the industry ) between say 0.5
for shallow dishes to .25 for deep dishes terminated at latus rectum,
normal value is around 0.3.

Regards
Narasimham

Xah Lee <xah@...> wrote:
just created this page:
http://xahlee.org/Whirlwheel_dir/reflecting_disks/reflecting_disks.html

a photo gallery of reflecting disks. (radio dishes, solar dishes)

Xah