People keep upgrading their PC monitors, and a lot of monitor cables are being thrown away. First  VGA, and now DVI. Many of them have EMI suppression ferrite cores of various sizes.
They come essentially for free if you know where to look. I accumulated a dozen or so of these, planned to use them for common mode suppression chokes. The material is unknown, but seems to work well on HF frequencies.
Have anybody in this group tried to use these cores in a loopstick antenna? They can be glued together to form a "rod" of sorts.

73, Mike AF7KR