Active antennas are of interest to a wide range of users, from shortwave listeners (SWLs) and radio amateurs to designers of aircraft radios. SWLs and radio amateurs living in confined areas such as apartments or in communities having antenna restrictions find small antennas and especially active antennas to be a practical solution.
Physically small antennas that have a directional radiation pattern can be very useful when nulling out interference is desired. Small loop antennas have this characteristic, and small shielded loop antennas provide a good degree of immunity from low frequency electric field noise, which is highly desireable in urban environments. Both forms of loop antennas require some form of tuning in order to accomodate
the high inductive reactance of the terminal ipedance. Designs that employ parallel tuning require an amplifier to couple the resultant high antenna impedance to the feed line, while those that employ series tuning can be passively matched to the feedline and have exceptional noise figure (NF) and intermodulation distortion (IMD) performance.
The purpose of this paper is to present an alternative small directional antenna that is capable of both wideband and tuned narrow-band perfromance and which can be made with readily available and inexpensive parts and materials.