Cost estimate: $8

Here is a simple electronic alternative for those lacking space to string up 30-50 ft. of wire for reception of shortwave radio signals. The performance of this streamlined active antenna rivals that of my outdoor dipole .

Construction & Operation:The photo and schematic are pretty much self-explanatory; the only oddball part is the miniature choke. For shortwave frequencies any value around 50uH should perform well, but if out-of-band interference is experienced replace it with a choke of lower value. Use a higher value coil (about 470uH) for improved performance of broadcast AM radios. Make all connections as short as possible and be sure to ground the unit when using it with receivers that require ground connections such as the Simplest Ham Receiver.

Source:
Covington, Michael A. N4TMI, "AM/FM/SW ACTIVE ANTENNA" 
     Popular Electronics, Vol.6, No.7, July 1989, pp.73 & 106