Active Antenna for AM/FM/SW

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 30foot wire antenna. It is further more designed to be used on receivers that use untuned wire antennas, such as inexpensive units and car radios.

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

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 input on the receiver.

FM Radio Antenna Amplifier

Active FM-Amplifier:

With only a small handful of parts you can built this trusty FM Amplifier. It works with only 1 UHF/VHF type transistor, MFE201. This amplifier will pull in all distant FM stations clearly. The circuit is configured as a common-emitter tuned RF pre-amplifier wired around VHF/UHF transistor MFE201. There are a couple other models that probably would work too, like the NTE107, 2SC2570, etc. but I have not tried it.

Adjust capacitor trimmers C1 and C2 for maximum gain. Input coil L1 consists of 4 turns of 20SWG enameled copper wire over a 5mm diameter former. It is tapped at the first turn from ground lead side. Coil L2 is similar to L1, but has onlythree turns. Pin configuration is shown in the diagram.

99.6MHZ J-power FM transmitter antenna

99.6MHZ J-Power FM transmitter antenna

99.6MHZ J-power FM transmitter antenna 99.6MHZ J-power FM transmitter antenna

10 mm diameter brass refrigeration production with a total length of 3.5 M 10 mm diameter brass refrigeration production with a total length of 3.5 M

Active Antenna AA-7 HF/VHF/UHF, 3-3000MHz

If you have a shortwave or high-frequency receiver or scanner that is struggling to capture signals with a short, whip antenna, and you'd like the kind of performance that a 60-foot 'longwire' antenna can provide but lack the space to put one up, consider building the AA-7 HF/VHF/UHF Active Antenna described in this article. The AA-7 is a relatively simple antenna that is designed to amplify signals from 3 to 3000 MegaHertz, including three recognized ranges: 3-30Mhz high-frequency (HF) signals; 3-300Mhz very-high frequency (VHF) signals; 300-3000MHz ultra-high (UHF) frequency signals. Those bands are typically occupied by shortwave, ham, government, and commercial radio signals.

Active Antenna

An antenna with an integrated RF pre - amplifier