Cost estimate: $12
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
Construction & Operation: Solder the electronic components on a circuit board
and put it inside a small project box (be sure to leave room for the battery). Mount the switch, jack, and
antenna (an 18" telescoping kind looks best, but a stiff wire will do) on the box.
Attach the output to the receiver's corresponding connections and flip the switch - that's all.
Keep all connections as short as possible. The diagram is
pretty much self-explanatory; the only oddball
part is the miniature choke. For shortwave frequencies any value around 50uH (microhenries)
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.
Covington, Michael A. N4TMI, "AM/FM/SW ACTIVE ANTENNA"
Popular Electronics, Vol.6, No.7, July 1989, pp.73 & 106