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02-10-2007

Active Antenna for AM, FM, SW

"Popular Electronics" magazine, July 1989

This simple little circuit can be used for AM, FM, and Shortwave(SW). On the shortwave band this active antenna is comparable to a 20 to 30 foot wire antenna. It is further more designed to be used on receivers that use untuned wire antennas, such as inexpensive units and car radios.

simple little circuit antenna AM, FM, SW

Parts List:

  • R1 = 1 M
  • C1 = 470 pF
  • C2 = 470 pF
  • L1 = see text
  • Q1 = MPF102, or NTE451

L1 can be selected for the application. A 470 uH coil works on lower frequencies and lie in AM, for shortwave try a 20 uH coil. This unit can be powered by a 9 volt alkaline battery. If a power supply is used, bypass the power supply with a 0.04 uF 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.

JFET-N-Channel UHF/VHF amplifier NTE451

The heart of this circuit is Q1, a JFET-N-Channel, UHF/VHF amplifier in a TO-92 case. It can be replaced with an NTE451.

Output is taken from jack J1 and run to the antenna-input of your receiver.

printed circuit board antenna

layout diagram antenna

Although this little circuit can easily be mounted on a piece of vero-board, I have supplied the printed circuit board and layout diagram if you wish to make a printed circuit board.

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