Effect of shields on ferrites
A simple S21 test reveals conductive shields do not change the behavior or ability of a ferrite to perform the role of common-mode rf current choke.
type 61
Fair-Rite 2661480002 Type 61 Ferrite Slide-on Chokes
A closer look at type 61 ferrite material in various configurations for RG58 reveals the benefits and insufficiencies of chokes in series.