My “antenna” (if you can call it that) for short-wave listening, is thrown together using an indeterminate length of “speaker”-wire I scrounged from somewhere-or-other. It was your typical conductor (stranded) stuff. I just pulled the two conductors apart, and combined them into what is effectively one length of wire, arranged in a configuration that (vaguely) approximates the number “7” (a straight length, with one end eye-bolted into a nearby tree, with the second length of wire run through a hole, into the house here.
For what it is, it “works” (after a fashion). At first, I believed that my RFI issues were mostly related to the switching power-supply “wall wart” for the cable-modem, so I got some of those clip-on RFI-suppressor toroids.
Adding those to the power-cord (and the power-cord for the charging unit for the cordless phone, did — something: it reduced the RFI from the cable-modem enough for me to to notice the fact that my (crappy) antenna was hearing the house-wiring. (Something at least vaguely approximating 60-cycle hum from approximately 1600 hz. to 6000 or so.
I may have to attempt to build an “unun”, if possible.