couple alligator clips and a slinky toy will do in a pinch. although it is possible to construct a jam-proof and noise-reducing antenna for shortwave with a few strips of aluminum foil and some paper or wax paper (ideally). It lays flat on a floor or bed, and you "tune" it by moving the "frame" shape closer or further apart. there's a book involved.

It was used to have secret, covert, etc radios. It's believed to be used by assets in the field to receive numbers stations, especially when there's a lot of man made noise in the area.