Scalar rings are under "image rejection" when it comes to satellite
signal reception. When the wave, (which looks to the dish like a "s"
or "z"), enters the focal point of the feed, the satellite you want
signals should be the "S" or "Z" wave only located on the inside of
the feedhorns round middle part, which is its' waveguide. The scalar
rings reject any other satellites, or any other signal, of the same
wavelength, or larger wavelength (which in satellite signal terms is
lower or high in freq.) reflected from the middle of the dish, by
absorbing and intercepting these "larger" waves, not allowing them
to enter the middle of the feedhorn where the wanted signals are.
That is about all I can say about the "scalar" rings mounted on a
feedhorn. These other rejected signals can be point-to-point towers
on the same, or lower frequencies, that carry communications to
different areas; or it can be an adjacent satellite signal not rejected
by the dish itself, which if it does not have its' main lobe of signal
within 2 degrees of the wanted satellite, does pick up signal from
the adjacent one. This has to do with both the dishes design (F/D),
and its size (say 7 campared to 10 feet in diameter) which gives
the dish its beamwidth, the amount the main lobe of the dish picks
up in degrees of width, like 2 or 3 or 4 degrees, depending on its
size and design of F/D.
It boost the signal by10-15% and it works Ku and cband...