A simple active hidden antenna
computer science crazy|
Joined: Dec 2008
28-11-2009, 06:23 PM
This circuit shows an active antenna that 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. [img]hard-core-dxnordicdx/antenna/hidden/active2.gif[/img]
This circuit is 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 470uH coil works on lower frequencies ( AM ). For shortwave, try a 20uH coil.
The unit can be powered by a 9 volt battery. If a power supply is used, bypass the power supply with a .04uF capacitor to prevent noise pickup.
The antenna used on this circuit is a standard 18" telescoping type.
Output is taken from jack J1 and run to the input on the receiver.
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