Ferrite Cores. Wrap a tube of 24wt printer paper around the antenna itself. Flush the PVC tubes. Secure with Scotch tape. Apply a layer of copper foil tape, available on Amazon, which you can solder to... or aluminum tape, from Lowes, which you can't. Leave a tiny gap length ways. Don't cover the ends. Ground alum tape with an 'S' bend of wire, secured with a patch of the same alum tape. Ground it to the amp antenna ground. Shielding ain't gonna work with Navy transmitters. or other M signals, if they're that close.
Ya can't shield E field Probe.
If it don't work, you can simply tear off the printer paper tube, flush it, and the 'shielding' and find other mediation. And you won't screw over your pretty ferrites.
Been There. Done That. Designed the Tee Shirt, which are available on a PM request.