Title: AM/FM/SW active antenna
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. 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.
Source: "Popular Electronics" Magazine, Jul,89 issue. (C)Copyright
Gernsback Publications,Inc., 1989 - Please read their disclaimers before
implementing this circuit.