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.
S21
Where a choke chokes
I measure one example of a ferrite coax choke for response over frequency to understand its suitability for VHF and UHF.
Aluminum RF power splitters under test
Two examples of square aluminum RF power splitters built from 1973 plans reveal a 15 MHz difference from the claimed design frequency.