This AM/FM antenna booster circuit amplify the broadband signal from antenna. This antenna booster should work fro FM, AM, and SW receivers. Here is the schematic diagram of the circuit:
Using this antenna booster circuit, for short wave reception, an 8″ antenna would produce a strong signal level equivalent to a 20 to 30 feet wire antenna. This antenna booster circuit is designed for general radio receiver, which its antenna is not tuned for specific frequency but for a wide band frequency. Try around 470uH for L1 coil for AM, and around 20uH for shortwave or FM frequency band. Use a standard 18″ telescoping type for this booster circuit. Bypass the supply to ground using 47nF capacitor? as close as possible to the L1 coil to prevent any noise picked up from the power cable. Install this booster circuit as close as possible to the antenna, shorter cables for better performance.
Source: http://www.hqew.net/circuit-diagram/Antenna-Booster-for-FM$2c-AM$2c-and-SW-Receiver_3397.html
