Conical Scalar Ring vs. Scaler Ring

[spongella]

When using mini-Buds most folks use a conical scalar ring vs. just a regular scalar ring. What is the scientific/physical basis for this, does the shape of the conical, which resembles a funnel, channel more signal to the LNB due to it's shape or is it a type of wave guide of smaller concentric circles that channel the signal in a specific way?

If one made a larger conical scalar ring, let's say 50% bigger, would it work better? I'd imagine up to a certain extent, but size would be a problem. Has anyone out there home brewed their own conical scalar ring?

 

[Magic Static]

Conical scalars are designed for offset dishes and flat scalars are designed for prime focus dishes.

 

[Titanium]

Scalars are not signal funnels, they are tuned frequency chokes. A conical scalar design is used for high FD reflectors and a flat scalar for lower FD. The purpose is to accept only desired (on axis) signals from the reflector surface. Off axis signals are nulled and defused. Over-illuminate past the reflector edges and terrestrial noise is introduced. Under-illuminate, and the feedhorn is not receiving all of the reflected signals.

There have been several scalar discussions on the forum over the years, but this description by AcWxRadar is very well done:
http://www.satelliteguys.us/xen/posts/2322382/

Many homemade or modified scalar projects on this and other forums.

 

[FaT Air]

FWIW: The door of your microwave oven also has a 1/4? slot around the door perimeter. Traps in 'seals in' the RF energy. Works under the same principle.