This simple AM/FM/SW Active Antenna circuit are able to be used for AM, FM, and Shortwave(SW). For the shortwave band, this kind of active antenna is comparable to a 20 to 30 ft wire antenna. It’s in addition designed to be used on receivers which use untuned wire antennas, for example cheap models and car radios.
L1 can be chosen for the application. A 470µH coil works on lower frequencies and lie in Am, for shortwave try a 20µH coil. This AM/FM/SW Active Antenna circuit can be powered by a 9 volt battery pack. If a power supply is used, bypass the power supply using a 0.04µF capacitor to prevent noise pickup. The antenna used on this circuit is a standard 18-inch telescoping type, but a thick piece of copper, bus-bar, or piano wire will also work fine.
