This easy small circuit could be applied for AM, FM, and Shortwave(SW). On the shortwave band, this kind of active antenna is similar to a 20 to 30 foot wire antenna. It is additional more designed to be put into use on receivers which use untuned cable antennas, like affordable units and automobile radios.
L1 can be selected for the application. A 470µH coil functions on lower frequencies and lie in AM, for shortwave try a 20µH coil. This unit could be powered by a 9 volt alkaline battery. If a power supply is used, bypass the power supply having a 0.04µF capacitor to stop noise pickup. The antenna that being 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.
The main of this circuit is Q1, a JFET-N-Channel, UHF/VHF amplifier in a TO-92 case. It can be changed with an NTE451. The output is taken from jack J1 and should be connected to the input of the receiver.