Ferrite core Amidon FT-140-43. Works down to 1.8MHz. Note the winding style for
2 x 9 turns PTFE wire held in parallel. Common mode reactance
XL = firstname.lastname@example.orgMHz and email@example.comMHz
Coaxial connector screwed to insulation support. I don't use
any water shield, it will last long without that.
Toroidal core fixed with straps thru the support. Extra holes
will arrest the antenna wires.